TY - CONF A1 - Mishurova, Tatiana T1 - 3D imaging and residual stress analysis of AM materials at BAM N2 - The overview of the activity of group 8.5 Micro-NDT (BAM, Belin, Germany) in the field of additively manufacturing material characterization will be presented. The research of our group is focused on the 3D imaging of AM materials by means of X-ray Computed Tomography at the lab and at synchrotron, and the residual stress characterization by diffraction (nondestructive technique). T2 - Seminar at Chalmers University and Centre for Additive Manufacture (CAM2) CY - Gothenburg, Sweden DA - 19.05.2022 KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress KW - Computed tomography KW - Synchrotron X-ray diffraction KW - X-ray refraction PY - 2022 AN - OPUS4-55019 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Serrano Munoz, Itziar T1 - Multiscale residual stress analysis and synchrotron X-ray refraction of additively manufactured parts N2 - The overview of the activity of group 8.5 Micro-NDT (BAM, Belin, Germany) in the field of additively manufacturing material characterization will be presented. The challenges in the residual stress analysis of AM components are discussed on the basis on the show studies performed in BAM. Also, the synchrotron X-ray refraction technique, available in BAM, is presented, showing example of in-situ heating test of Al10SiMg AM material. T2 - Seminar at Grenoble INP, Science et Ingénierie des Matériaux et Procédés (SIMaP) CY - Grenoble, France DA - 01.07.2022 KW - Additive manufacturing KW - Residual stress KW - X-ray refraction KW - Computed tomography PY - 2022 AN - OPUS4-55232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Bruno, Giovanni A1 - Mishurova, Tatiana A1 - Serrano Munoz, Itziar A1 - Roveda, Ilaria A1 - Fritsch, Tobias A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Schröder, Jakob T1 - Residual stresses and micromechanical properties of additively manufactured metals: why do we need a paradigm shift? N2 - An overview of the challenges and successes in the methodology to characherise residual stresses and micromechnical properties in additively manufactured metals T2 - CAM2 Annual Seminar 2022 - 5-year journey CY - Gothenburg, Sweden DA - 24.10.2022 KW - Additive Manufacturing KW - Residual stress KW - AGIL KW - MANUFACT KW - Micromechnical properties PY - 2022 AN - OPUS4-56466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Mishurova, Tatiana T1 - Influence of residual stress and microstructure on mechanical performance of LPBF TI-6AL-4V N2 - Additive manufacturing technologies provide unique possibilities in the production of topologically optimized, near-net shape components. The main limiting factors affecting the structural integrity of Laser Powder Bed Fusion (LPBF) parts are manufacturing defects and residual stress (RS) because both of them are virtually inevitable. Taking into account the complex thermal history of LPBF materials, a prediction of the material behavior is not possible without experimental data on the microstructure, defect distribution, and RS fields. Therefore, this thesis aims to understand the factors that influence the LPBF Ti-6Al-4V material performance the most, covering both the production and the post-processing steps of manufacturing. Indeed, a parametric study on the influence of manufacturing process and post-processing on RS, defects and microstructure was performed. It was found that the volumetric energy Density (EV), commonly used for the LPBF process optimization, does neither consider the pore shapes and distribution, nor the influence of individual parameters on the volume fraction of pores. Therefore, it was recommended not to use EV without great care. It was shown that the Position on the base plate has a great impact on the amount of RS in the part. The micromechanical behavior of LPBF Ti-6Al-4V was also studied using in-situ Synchrotron X-ray diffraction during tensile and compression tests. Diffraction elastic constants (DEC), connecting macroscopic stress and (micro) strain, of the LPBF Ti-6Al-4V showed a difference from the DEC of conventionally manufactured alloy. This fact was attributed to the peculiar microstructure and crystallographic texture. It was therefore recommended to determine experimentally DECs whenever possible. Low Cycle Fatigue (LCF) tests at a chosen operating temperature were performed to evaluate the effect of post-treatment on the mechanical performance. Through the information on the microstructure, the mesostructure, and the RS, the LCF behavior was (indirectly) correlated to the process parameters. It was found that the fatigue performance of LPBF samples subjected to hot isostatic pressing is similar to that of hot-formed Ti-6Al-4V. The tensile RS found at the surface of LPBF as-built samples decreased the fatigue life compared to the heat-treated samples. The modification of the microstructure (by heat treatment) did not affect the Fatigue performance in the elastic regime. This shows that in the absence of tensile RS, the manufacturing defects solely control the failure of LPBF components and densification has the strongest effect on the improvement of the mechanical performance. KW - Additive manufacturing KW - Ti-6Al-4V KW - Residual stress KW - Computed tomography PY - 2021 SP - 1 EP - 143 CY - RWTH Aachen AN - OPUS4-54389 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Roveda, Ilaria A1 - Serrano Munoz, Itziar A1 - Kromm, Arne A1 - Madia, Mauro T1 - Investigation of residual stresses and microstructure effects on the fatigue behaviour of a L-PBF AlSi10Mg alloy N2 - Al-Si alloys produced by Laser Powder Bed Fusion (L-PBF) techniques allow the fabrication of lightweight free-shape components that find space in aerospace, automotive, biomedical and military applications. Due to the high cooling rates occurring during the building process, L-PBF AlSi10Mg alloys exhibit an ultra-fine microstructure that leads to superior mechanical properties in the as-built condition compared to conventional cast Al-Si materials. Nevertheless, L-PBF processing induces high thermal gradients, leading to deleterious residual stress levels that must be considered to avoid part distortion and unpredicted failures. In order to relax detrimental residual stress and to increase the ductility, post-processing stress relief treatments are generally performed. In as-built condition the hypoeutectic AlSi10Mg microstructure consist of fine α-Al cells containing uniformly dispersed silicon nanoparticles, which are, in addition, surrounded by a eutectic Si network. Above 260°C the silicon interconnectivity starts to breakdown into spheroidized particles and to coarsen. At the same time, the heating residual stresses are relieved. The objective of the contribution is to investigate, under different heat treatment conditions, the evolution of microstructure and residual stresses in view of optimizing the fatigue performance of the alloy. To this purpose various heat treatments in a range of temperatures between 265°C and 300°C for a duration between 15 minutes and 2 hours are performed. The microstructure modifications are analysed using a scanning electron microscope and the residual stress state is measured by laboratory X-ray diffraction. T2 - FATIGUE DESIGN 2021 CY - Online meeting DA - 17.11.2021 KW - AlSi10Mg alloy KW - Additive manufacturing KW - L-PBF KW - Residual stress KW - Heat treatment PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-544942 SN - 2452-3216 VL - 38 SP - 564 EP - 571 PB - Elsevier B.V. AN - OPUS4-54494 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Mishurova, Tatiana A1 - Serrano Munoz, Itziar A1 - Fritsch, Tobias A1 - Schröder, Jakob A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Residual Stresses in Additive Manufacturing (L-PBF) N2 - Additive manufacturing (AM) technologies are experiencing an exceedingly rapid growth, driven by their potential through layer wise deposition for transformational improvements of engineering design, leading to efficiency and performance improvements. Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing (AM) method which permits the fabrication of complex structures that cannot otherwise be produced via conventional subtractive manufacturing methods. Nevertheless, the rapid cooling rates associated with this process results in the formation of significant and complex residual stress (RS) fields. A large body of both experimental and simulation research has been dedicated in recent years to the control and mitigation of RS in AM. In order to validate simulations with the end goal of being able to model the residual stress state in AM components and to devise strategies for their reduction during manufacturing, experimental methods need to be able to accurately determine 3D residual stresses fields in complex geometries. Several destructive and non-destructive methods can be used to analyze the RS state, the choice of which depends on the geometry and the information required. Diffraction-based methods using penetrating neutron and synchrotron X-rays at large scale facilities offer the possibility to non-destructively spatially resolve both surface and bulk residual stresses in complex components and track their changes following applied thermal or mechanical loads. This presentation will overview the success stories of using large scale facilities by the BAM for the characterization of residual stresses in additively manufactured metallic alloys. In particular, the study of the influence of process parameters on the residual stress state and the relaxation of these stresses through heat treatment will be presented. However there remains challenges to overcome particularly of the hypotheses underlying the experimental determination of residual stresses, which will be discussed. T2 - 10th International Conference on Mechanical Stress Evaluation by Neutron and Synchrotron Radiation – MECASENS 2021 CY - Prague, Czech Republic DA - 25.11.2021 KW - Residual stress KW - Additive manufacturing KW - Diffraction KW - L-PBF KW - AGIL PY - 2021 AN - OPUS4-54105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Mishurova, Tatiana A1 - Serrano Munoz, Itziar A1 - Fritsch, Tobias A1 - Schröder, Jakob A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Residual Stresses in Additive Manufacturing (L-PBF) N2 - Metal Additive manufacturing (AM) technologies such as Laser Powder Bed Fusion (LPBF) enable the fabrication of complex structures, giving rise to potential improvements in component and manufacturing efficiency. However, the processes are typically characterized by the generation of high magnitude residual stress (RS) which can have detrimental consequences for subsequent applications. Therefore, the characterization of these RS fields and the understanding of their formation and mitigation through optimized processing is crucial for the wider uptake of the technology. Due to the potential complex nature and high value of components manufactured by LPBF, it is important to have suitable characterisation methods which can determine the spatial variations of RS in a non-destructive manner. Neutron diffraction is considered to be the best suited for these requirements. However, the microstructures developed in the complex thermal cycles experience in the production can pose challenges to the ND method for RS analysis. The BAM has conducted significant research over the past years to overcome these obstacles, enabling higher confidence in the RS determined in LPBF materials by neutron diffraction. This contribution will overview some of these advancements made recently at European neutron sources including on Stress-Spec at FRM2/MLZ. T2 - MLZ User Meeting 2021 CY - Online meeting DA - 07.12.2021 KW - Residual stress KW - Additive manufacturing KW - Diffraction KW - AGIL KW - Manufact PY - 2021 AN - OPUS4-54044 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Roveda, Ilaria A1 - Serrano Munoz, Itziar A1 - Kromm, Arne A1 - Madia, Mauro T1 - Investigation of residual stresses and microstructure effects on the fatigue behaviour of a L-PBF AlSi10Mg alloy N2 - Al-Si alloys produced by Laser Powder Bed Fusion (L-PBF) techniques allow the fabrication of lightweight free-shape components. Due to the high cooling rates occurring during the building process, L-PBF AlSi10Mg alloys exhibit an ultra-fine microstructure that leads to superior mechanical properties in the as-built condition compared to conventional cast Al-Si materials. Nevertheless, L-PBF processing induces high thermal gradients, leading to deleterious residual stress. In order to relax detrimental residual stress and to increase the ductility, post-processing stress relief treatments are performed. The objective of the contribution is to investigate, under different heat treatment condition, the evolution of microstructure and residual stresses in view of optimizing the fatigue performance of the alloy. To this purpose various heat treatments in a range of temperatures between 265°C and 300°C for a duration between 15 minutes and 2 hours are performed. T2 - Fatigue Design 2021 CY - Senlis, France DA - 17.11.2021 KW - AlSi10Mg KW - Additive manufacturing KW - L-PBF KW - Residual stress KW - Heat treatment PY - 2021 AN - OPUS4-53794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Fritsch, Tobias T1 - A Multiscale Analysis of Additively Manufactured Lattice Structures N2 - Additive Manufacturing (AM) in terms of laser powder-bed fusion (L-PBF) offers new prospects regarding the design of parts and enables therefore the production of lattice structures. These lattice structures shall be implemented in various industrial applications (e.g. gas turbines) for reasons of material savings or cooling channels. However, internal defects, residual stress, and structural deviations from the nominal geometry are unavoidable. In this work, the structural integrity of lattice structures manufactured by means of L-PBF was non-destructively investigated on a multiscale approach. A workflow for quantitative 3D powder analysis in terms of particle size, particle shape, particle porosity, inter-particle distance and packing density was established. Synchrotron computed tomography (CT) was used to correlate the packing density with the particle size and particle shape. It was also observed that at least about 50% of the powder porosity was released during production of the struts. Struts are the component of lattice structures and were investigated by means of laboratory CT. The focus was on the influence of the build angle on part porosity and surface quality. The surface topography analysis was advanced by the quantitative characterisation of re-entrant surface features. This characterisation was compared with conventional surface parameters showing their complementary information, but also the need for AM specific surface parameters. The mechanical behaviour of the lattice structure was investigated with in-situ CT under compression and successive digital volume correlation (DVC). The Deformation was found to be knot-dominated, and therefore the lattice folds unit cell layer wise. The residual stress was determined experimentally for the first time in such lattice structures. Neutron diffraction was used for the non-destructive 3D stress investigation. The principal stress directions and values were determined in dependence of the number of measured directions. While a significant uni-axial stress state was found in the strut, a more hydrostatic stress state was found in the knot. In both cases, strut and knot, seven directions were at least needed to find reliable principal stress directions. KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress KW - Surface roughness analysis KW - Computed tomography PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-470418 SP - 1 EP - 97 PB - Universitätsbibliothek Potsdam CY - Potsdam AN - OPUS4-53476 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pauzon, C. A1 - Mishurova, Tatiana A1 - Evsevleev, Sergei A1 - Dubiez-Le Goff, S. A1 - Murugesan, S. A1 - Bruno, Giovanni A1 - Hryha, E. T1 - Residual stresses and porosity in Ti-6Al-4V produced by laser powder bed fusion as a function of process atmosphere and component design N2 - The influence of the process gas, laser scan speed, and sample thickness on the build-up of residual stresses and porosity in Ti-6Al-4V produced by laser powder bed fusion was studied. Pure argon and helium, as well as a mixture of those (30% helium), were employed to establish process atmospheres with a low residual Oxygen content of 100 ppm O2. The results highlight that the subsurface residual stresses measured by X-ray diffraction were significantly lower in the thin samples (220 MPa) than in the cuboid samples (645 MPa). This difference was attributed to the shorter laser vector length, resulting in heat accumulation and thus in-situ stress relief. The addition of helium to the process gas did not introduce additional subsurface residual stresses in the simple geometries, even for the increased scanning speed. Finally, larger deflection was found in the cantilever built under helium (after removal from the baseplate), than in those produced under argon and an argon-helium mixture. This result demonstrates that complex designs involving large scanned areas could be subjected to higher residual stress when manufactured under helium due to the gas’s high thermal conductivity, heat capacity, and thermal diffusivity. KW - Additive manufacturing KW - Ti-6Al-4V KW - Residual stress KW - Process atmosphere KW - Helium PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-534209 VL - 47 SP - 2340 PB - Elsevier B.V. AN - OPUS4-53420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander A1 - Altenburg, Simon A1 - Mohr, Gunther A1 - Oster, Simon A1 - Sprengel, Maximilian T1 - Tales from Within: Residual Stress and Void Formation in LPBF 316L N2 - An unusual microstructure, inherent residual stresses and void formation are the three key aspects to control when assessing metallic parts made by LPBF. This talk explains an experiment to unravel the interlinked influence of the two mechanisms for the formation of residual stresses in LPBF: the temperature gradient mechanism and constricted solidification shrinkage. The impact of each mechanism on the shape and magnitudes of the residual stress distribution is described. Combined results from neutron diffraction, X-ray diffraction, computed tomography and in-situ thermography are presented. Also, influence of scan strategies as well as surface roughness of subjacent layers on void formation is shown. Results from computed tomography and in-situ thermography of a specimen dedicated to study the interaction of the melt pool with layers of powder underneath the currently illuminated surface are presented. T2 - 2nd Workshop on In-situ Monitoring and Microstructure Development in Additive Manufacturing CY - Online meeting DA - 19.04.2021 KW - Neutron diffraction KW - Laser powder bed fusion KW - In-situ thermography KW - Computed tomography KW - X-ray diffraction KW - Residual stress KW - Pore formation KW - AISI 316L PY - 2021 AN - OPUS4-52819 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Launert, B. A1 - Rhode, Michael A1 - Kromm, Arne A1 - Pasternak, H. A1 - Kannengießer, Thomas T1 - Measurement and numerical modeling of residual stress distribution in welded HSLA component-like I-girders N2 - Welded I-girders are used in many applications in steel construction, especially a tailored mixture of different plate thicknesses is difficult to manufacture by rolling. Residual stresses are mainly caused by welding and it is in most cases impractical to anneal the structures. Eurocode 3 (EC 3) does not provide any specific residual stress pattern. Hence, the decision for a particular problem has to be taken by the designer. Stability failures are often decisive in the design of steel beam and column members. Many standards, including EC 3, permit the use of non-linear FEA for the design of structures. Load influencing imperfections are mainly geometric deviations from the ideal shape and residual stresses(both due to assembly or weld manufacturing). Currently the residual stresses are considered by simplified “robust” procedures fixed in common standards(such as EC 3. Models mostly based on specimens from mild steel. Information about high-strength steels is less available for realistic assessment of residual stresses in full-scale I-girders. Hence, the scope of this work is the measurement of residual welding stresses on component-like I-girders S355 and S690 by sectioning method and global structural welding simulation. T2 - 69th IIW Annual Assembly, Meeting of Subcommission II-A CY - Melbourne, Australia DA - 10.07.2016 KW - Residual stress KW - Welding KW - Load bearing capacity KW - Numerical modeling KW - Measurement PY - 2016 AN - OPUS4-37025 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dixneit, Jonny A1 - Kromm, Arne A1 - Boin, M. A1 - Kannengießer, Thomas A1 - Gibmeier, J. T1 - Influence of heat control on residual stresses in low transformation temperature (LTT) large scale welds N2 - Independent from the interpass temperature residual stresses in longitudinal direction were lower than in transverse direction. This applies for the surface as well as for the bulk of the welds. Residual stresses in the bulk were in general lower compared to stresses found on the surface. Compressive residual stresses as a result of the martensite formation were formed in the bulk weld metal, only. Independent from the LTT filler used high interpass temperatures were beneficial to reduce the stresses mainly in longitudinal direction. Lower interpass temperatures tend to narrow the tensile zone in the weld metal but they also prevent the formation of compressive residual stresses. T2 - ICRS10 CY - Sydney, Australia DA - 03.07.2016 KW - Phase transformation KW - LTT KW - Welding KW - Heat control KW - Residual stress PY - 2016 AN - OPUS4-37312 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dixneit, Jonny A1 - Kromm, Arne A1 - Boin, M. A1 - Kannengießer, Thomas A1 - Gibmeier, J. T1 - Effect of interpass temperature on residual stresses in LTT welded joints N2 - Independent from the interpasstemperature residual stresses in longitudinal direction were lower than in transverse direction. This applies for the surface as well as for the bulk of the welds. -Residual stresses in the bulk were in general lower compared to stresses found on the surface. •Compressive residual stresses as a result of the martensite formation were formed in the bulk weld metal, only. •Independent from the LTT filler used high interpasstemperatures were beneficial to reduce the stresses mainly in longitudinal direction. •Lower interpasstemperatures tend to narrow the tensile zone in the weld metal but they also prevent the formation of compressive residual stresses. T2 - IIW2016 CY - Melbourne, Australia DA - 10.07.2016 KW - Phase transformation KW - Interpass temperature KW - LTT KW - Residual stress KW - Welding PY - 2016 AN - OPUS4-37313 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Schasse, R. A1 - Xu, Ping A1 - Mente, Tobias A1 - Kannengießer, Thomas T1 - Influence of weld repair by gouging on the residual stresses in high strength steels N2 - Carbon arc-air gouging is a common technology when repairing defects in welded structures. Often this technique is applied in repeated cycles even on the same location of the joint. Due to the multiple heat input by gouging and subsequent re-welding, the residual stresses are strongly influenced. This can become crucial when microstructure and mechanical properties are adversely affected by multiple weld reparations. Knowledge about the relation of gouging and residual stresses is scarce but important when high strength steels, which are sensitive to residual stresses, are processed. The present study shows the effect of repair welding on a high strength steel structural element. The weld and the heat affected zone were subjected to multiple thermal cycles by gouging and subsequent repair welding. The residual stresses were determined by X-ray diffraction at different positions along the joint. The results showed that the residual stress level has increased by the repair cycles. This is most pronounced for the heat affected zone. Adapted welding procedures may prevent detrimental residual stress distributions. T2 - International Conference on Residual Stresses 10 CY - Sydney, Australia DA - 03.07.2016 KW - Repair welding KW - Residual stress KW - Carbon arc-air gouging PY - 2016 AN - OPUS4-36886 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Rhode, Michael A1 - Launert, B. A1 - Dixneit, Jonny A1 - Kannengießer, Thomas A1 - Pasternak, H. T1 - Combining sectioning method and x-ray diffraction for evaluation of residual stresses in welded high strength steel components N2 - Residual stresses and distortions in welded I-girders for steel construction are relevant when evaluating the stability of steel beams and column members. The application of high strength steels allows smaller wall thicknesses compared to conventional steels. Therefore, the risk of buckling has to be considered carefully. Due to the lack of knowledge concerning the residual stresses present after welding in high strength steel components conservative assumptions of their level and distribution is typically applied. In this study I-girders made of steels showing strengths of 355 MPa and 690 MPa were welded with varying heat input. Due to the dimension of the I-girders and the complex geometry the accessibility for residual stress measurement using X-ray diffraction was limited. Therefore, saw cutting accompanied by strain gauge measurement has been used to produce smaller sections appropriate to apply X-ray diffraction. The stress relaxation measured by strain gauges has been added to residual stresses determined by X-ray diffraction to obtain the original stress level and distribution before sectioning. The combination of both techniques can produce robust residual stress values. From practical point of view afford for strain gauge application can be limited to a number of measuring positions solely to record the global amount of stress relaxation. X-ray diffraction can be applied after sectioning to determine the residual stresses with sufficient spatial resolution. T2 - International Conference on Residual Stresses 10 CY - Sydney, Australia DA - 03.07.2016 KW - Residual stress KW - Sectioning method KW - X-ray diffraction PY - 2016 AN - OPUS4-36887 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dixneit, Jonny A1 - Kromm, Arne A1 - Hannemann, Andreas A1 - Friedersdorf, Peter A1 - Kannengießer, Thomas A1 - Gibmeier, J. T1 - In-situ load analysis in multi-run welding using LTT filler materials N2 - Modifying the level of mostly detrimental welding residual stresses already during the welding process would be highly attractive as time- and cost-consuming post processing may be prevented. The nature of stress buildup during welding-associated cooling is highly affected by phase transformations. Up to now, it is not clear in which way this is applicable to real component welding exhibiting high shrinkage restraint and complex heat input. In this study, two different low transformation temperature (LTT) alloys have been investigated concerning the stress development in restrained multi-run butt welding in order to evaluate the potential of stress reduction. Pulsed gas metal arc welding (P-GMAW) welding was executed on a testing facility designed to simulate real lifelike restraint conditions of component weldments. The effect of reducedMS-temperatures and the heat control on the globally acting stresses was monitored by in-situ measurement of the reaction forces during welding fabrication. Additional local residual stress measurements allowed analyzing global as well as local loading of the welded construction. Although phase transformation has a significant influence on unloading the joint during each weld pass, the reaction stress upon cooling to room temperature seems to be determined mainly by the heat input. On the surface, low longitudinal residual stresses were observed in case of LTT whereas transverse residual stresses are less affected. T2 - 69th IIW Annual Assembly and International Conference CY - Melbourne, Australia DA - 10.07.2016 KW - Phase transformation temperature KW - Residual stress KW - Welding KW - Dilution KW - Restraint PY - 2016 U6 - https://doi.org/10.1007/s40194-016-0373-1 SN - 0043-2288 VL - 60 IS - 6 SP - 1159 EP - 1168 PB - Springer CY - Heidelberg AN - OPUS4-37892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Nolze, Gert ED - Sen Gupta, S. P. ED - Chatterjee, P. T1 - The determination of residual stress N2 - X-ray stress analysis on crystalline materials is based on the determination of elastic lattice strains. The strains described by the shift of peak positions are converted to stresses by the means of theory of elasticity. The development of the sin2ψ-method of X-ray stress analysis introduced an enormous progress in X-ray stress analysis during the last decades. This report outlines some important elements of X-ray physics and fundamentals of theory of elasticity. The Standard measuring procedure are described and special experimental differences to the common powder diffractometry are outlined. KW - XRD KW - Residual stress PY - 2002 SN - 81-7764-262-6 SN - 9788177642629 SP - 77 EP - 83 PB - Allied Publishers CY - Kolkata, India AN - OPUS4-38036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dixneit, Jonny T1 - Observation of martensite formation by combined use of synchrotron diffraction and dilatometry N2 - Welding residual stress engineering by means of an adjusted martensite phase transformation would be highly attractive as detrimental tensile residual stresses may be prevented already during welding without time and cost intensive post processing. The present study shows a synchrotron diffraction analysis of a martensitic steel subjected to thermo-mechanical load cycles. Experiments were conducted regarding the microstructural strain response during the austenite to martensite transformation. The strains are a function of the temperature and the specific loads applied during cooling. The relation between the transformation plasticity of the material, the amount of martensite formed and the arising strains can thus be assessed. The lattice plane specific strains were compared to experimental findings from (macro) dilatation tests. It is shown that the microscopic material behavior differs remarkably from the one observed on the macroscopic scale, what leads to characteristic residual stresses in the material. T2 - Material Science & Technology (MS&T16) 3rd International Workshop of In-situ Studies with Photons, Neutrons and Electrons Scattering CY - Salt Lake City, UT, USA DA - 23.10.2016 KW - Residual stress KW - Martensite KW - Dilatometry KW - Synchrotron diffraction KW - Neutron diffraction PY - 2016 AN - OPUS4-37999 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Lyamkin, Viktor A1 - Bruno, Giovanni A1 - Wimpory, Robert A1 - Boin, Mirko A1 - Pittner, Andreas A1 - Kuffel, Mareike A1 - Kreutzbruck, Marc T1 - Characterization of residual stress state by neutron diffraction and residual magnetic field mapping N2 - Based on the residual stress characterization of tungsten inert gas welded S235JRC+C plates by means of neutron diffraction, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors is discussed. The experiments performed indicate a correlation of residual stress changes and local residual magnetic stray fields. T2 - Eighth Joint BER II and BESSY II User Meeting CY - Berlin, Germany DA - 07.12.2016 KW - Residual stress KW - Magnetic stray fields KW - GMR KW - Neutron diffraction PY - 2016 AN - OPUS4-38676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Lyamkin, V. A1 - Bruno, Giovanni A1 - Pittner, Andreas A1 - Wimpory, Robert A1 - Boin, M. A1 - Kreutzbruck, Marc T1 - Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings N2 - The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction(ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth. KW - GMR KW - Magnetic stray field KW - Neutron diffraction KW - Residual stress KW - TIG-welding PY - 2017 U6 - https://doi.org/10.1016/j.jmmm.2016.11.102 SN - 0304-8853 SN - 1873-4766 VL - 426 SP - 580 EP - 587 PB - Elsevier CY - Amsterdam AN - OPUS4-38678 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Bruno, Giovanni A1 - Artzt, Katia A1 - Haubrich, J. A1 - Requena, G. T1 - Surface residual stresses analysis in SLM Ti–6Al–4V bridges N2 - Selective Laser Melting (SLM) technique allows to produce parts with complex geometry. Due to the rapid solidification and heat gradient during production, SLM results in presence of residual stress. The present study shows the influence of manufacturing parameters on surface residual stress of Ti-6Al-4V SLM parts. High tensile stresses in the front surface are found. Heat Treatment conditions relax residual stresses almost to zero. High scanning speed during manufacturing results in higher tensile stresses in the surface. T2 - HZB User Meeting CY - BESSY II, Berlin, Germany DA - 08.12.2016 KW - Additive manufacturing KW - Residual stress KW - Selective laser melting PY - 2016 AN - OPUS4-38657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Bruno, Giovanni T1 - Residual stress characterization of IN718 part obtained by selective laser melting N2 - Additive Manufacturing (AM) by Selective Laser Melting (SLM) offers ample scope for producing geometrically complex parts as compared to the traditional subtractive manufacturing strategies. However, the residual stresses developed during the processing can reduce the load bearing capacity as well as induce unwanted distortion, limiting the application of SLM parts. IN718 manufactured by SLM process can show high tensile residual stresses in the surface as high as the yield strength of the wrought alloy. On the other hand, residual stresses in the bulk Show considerably lower stress values, even in compression, indicating a stress re-distribution during deposition of the SLM layers. T2 - HZB User meeting CY - BESSY II, Berlin, Germany DA - 08.12.2016 KW - Additive manufacturing KW - Residual stress KW - Selective laser melting KW - Neintron diffraction PY - 2016 AN - OPUS4-38660 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Sonntag, Nadja A1 - Waikom Singh, Sharatchandra A1 - Bruno, Giovanni A1 - Skortzki, Birgit A1 - Kreutzbruck, Marc T1 - Metal magnetic memory technique - prospects and restrictions N2 - Magnetic testing methods are frequently applied in non-destructive evaluation of ferromagnetic materials. In the past decade, metal magnetic memory (MMM) technique according to ISO 24497 is gaining considerable interest in the magnetic NDT community. In contrast to traditional Magnetic Flux Leakage (MFL) testing, the inspection objects are not intentionally magnetized by an external magnetic field. Due to physical coupling between mechanical stress and magnetization in ferromagnetic materials, it is assumed that the distribution of the “natural” MFL (self-magnetic-leakage field, SMLF) indicate zones of different remanent magnetization, which in turn, correspond to the internal stress of specimen or in the most general sense to material degradation. Usually, MMM measurements are performed by relatively bulky magnetic inspection sensors providing a spatial resolution in millimetre range. High precision GMR (Giant Magneto Resistance) measurements in the micrometer regime along with image based representation and evaluation can provide a higher degree of information. We present a concise summary of a broader research project aimed at studying the correlation of magnetic structure and microstructure of steels. Particularly, we compare residual stress measurements in S235JR steel by means of neutron diffraction with high resolution magnetic field measurements. In addition, we discuss the influence of deformation-induced magnetization in plastically deformed specimens with and without notches due to various quasi-static and cyclic load levels. Furthermore, comparative measurements with common non-destructive testing methods are presented. Despite of a quantitative evaluation of material degradation, the in the field inspection by MMM remains problematic due to substantial influences on such as external magnetization, anisotropy of internal magnetization and material degradation, as well as geometry and surface effects of the inspection objects on SMFL signals. The prospects and restrictions of the MMM technique are discussed in this contribution. T2 - 19th World Conference on Non-Destructive Testing (WCNDT 2016) CY - Munich, Germany DA - 13.06.2016 KW - Materials characterisation KW - Standards and training (certification, qualification) KW - Residual stress KW - Magnetic testing KW - Neutron diffraction KW - GMR sensor (Giant Magneto Resistance) PY - 2016 AN - OPUS4-38356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cabeza, Sandra A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Bruno, Giovanni T1 - Development of residual stresses in IN718 parts obtained by SLM N2 - Additive Manufacturing by Selective Laser Melting (SLM) offers ample scope for producing geometrically complex parts as compared to the traditional subtractive manufacturing strategies. However, the residual stresses (RS) developed during the processing can reduce the load bearing capacity as well as induce unwanted distortion, limiting the application of SLM parts. In the present work, residual stresses in additivly manufactured IN718 part were analised by means of neutron diffraction and synchrotron X-ray diffraction. T2 - ISAM 2017 CY - Dresden, Germany DA - 07.02.2017 KW - Additive manufacturing KW - Residual stress KW - Inconel 718 KW - Netron diffraction KW - Microstructure PY - 2017 AN - OPUS4-39139 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiede, Tobias A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Bode, Johannes A1 - Haberland, C. A1 - Bruno, Giovanni T1 - An assessment of bulk residual stress in selective laser melted Inconel 718 N2 - Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. The residual stress distribution in the bulk of IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-build condition (on a build plate) and after removal from the build plate. The absolute values of all stress components decreased after removal from the build plate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component depending on the thermal gradient in the respective direction. T2 - ECNDT 2018 CY - Göteborg, Sweden DA - 11.06.2018 KW - Residual stress KW - Selective laser melting KW - Neutron diffraction KW - IN718 PY - 2018 UR - http://cdn.ecndt2018.com/wp-content/uploads/2018/05/ecndt-0315-2018-File001.pdf SP - 1 AN - OPUS4-45325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Artzt, Katia A1 - Bruno, Giovanni A1 - Haubrich, Jan A1 - Requena, Guillermo T1 - Subsurface Residual Stress Analysis in Ti-6Al-4V Additive Manufactured Parts by Synchrotron X-ray Diffraction N2 - Synchrotron X-ray diffraction is a powerful non-destructive technique for the analysis of the material stress-state. High cooling rates and heterogeneous temperature distributions during additive manufacturing lead to high residual stresses. These high residual stresses play a crucial role in the ability to achieve complex geometries with accuracy since they can promote distortion of parts during manufacturing. Furthermore, residual stresses are critical for the mechanical performance of parts in terms of durability and safety. In the present study, Ti-6Al-4V bridge-like specimens were manufactured additively by selective laser melting (SLM) under different laser scanning speed conditions in order to compare the effect of process energy density on the residual stress state. Subsurface residual stress analysis was conducted by means of synchrotron X-ray diffraction in energy dispersive mode for three conditions: as-built on base plate, released from base plate, and after heat treatment on the base plate. The quantitative residual stress characterization shows a correlation with the qualitative bridge curvature method. Computed tomography (CT) was carried out to ensure that no stress relief took place owing to the presence of porosity. CT allows obtaining spatial and size pores distribution which helps in optimization of the SLM process. High tensile residual stresses were found at the lateral surface for samples in the as-built conditions. We observed that higher laser energy density during fabrication leads to lower residual stresses. Samples in released condition showed redistribution of the stresses due to distortion. T2 - ECNDT 2018 CY - Göteborg, Sweden DA - 11.06.2018 KW - Additive manufacturing KW - Selective laser melting KW - Residual stress KW - Computed tomography KW - Ti-6Al-4V PY - 2018 AN - OPUS4-45202 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, Katia A1 - Bruno, Giovanni A1 - Requena, Guillermo A1 - Haubrich, Jan T1 - Subsurface residual stress analysis in Ti-6Al-4V additive manufactured parts by synchrotron x-ray diffraction N2 - Synchrotron X-ray diffraction is a powerful non-destructive technique for the analysis of the material stress-state. High cooling rates and heterogeneous temperature distributions during additive manufacturing lead to high residual stresses. These high residual stresses play a crucial role in the ability to achieve complex geometries with accuracy since they can promote distortion of parts during manufacturing. Furthermore, residual stresses are critical for the mechanical performance of parts in terms of durability and safety. In the present study, Ti-6Al-4V bridge-like specimens were manufactured additively by selective laser melting (SLM) under different laser scanning speed conditions in order to compare the effect of process energy density on the residual stress state. Subsurface residual stress analysis was conducted by means of synchrotron X-ray diffraction in energy dispersive mode for three conditions: as-built on base plate, released from base plate, and after heat treatment on the base plate. The quantitative residual stress characterization shows a correlation with the qualitative bridge curvature method. Computed tomography (CT) was carried out to ensure that no stress relief took place owing to the presence of porosity. CT allows obtaining spatial and size pores distribution which helps in optimization of the SLM process. High tensile residual stresses were found at the lateral surface for samples in the as-built conditions. We observed that higher laser energy density during fabrication leads to lower residual stresses. Samples in released condition showed redistribution of the stresses due to distortion. T2 - 12th ECNDT 2018 CY - Göteborg, Sweden DA - 11.06.2018 KW - Additive manufacturing KW - Selective laser melting KW - Residual stress KW - Synchrotron X-ray diffraction KW - Ti-6Al-4V PY - 2018 UR - http://cdn.ecndt2018.com/wp-content/uploads/2018/05/ecndt-0213-2018-File001.pdf SP - 1 EP - 8 AN - OPUS4-45217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fernández, R. A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Fernández-Castrillo, P. A1 - González-Doncel, G. A1 - Bruno, Giovanni T1 - Residual stress and yield strength evolution with annealing treatments in an age-hardenable aluminum alloy matrix composite N2 - We investigated the possibility of minimizing tensile matrix residual stresses in age hardenable aluminum alloy metal matrix composites without detrimentally affect their mechanical properties (such as yield strength). Specifically, we performed thermal treatments at different temperatures and times in an age-hardenable aluminum matrix composite 2014Al-15vol%Al2O3. Using X-ray synchrotron radiation diffraction and mechanical tests, we show that below a certain treatment temperature (250 °C) it is possible to identify an appropriate thermal treatment capable of relaxing residual stress in this composite while even increasing its yield strength, with respect to the as processed conditions. KW - Residual stress KW - X-ray diffraction KW - Annealing treatment KW - Metal matrix composite KW - Yield strength PY - 2018 U6 - https://doi.org/10.1016/j.msea.2018.06.031 SN - 0921-5093 SN - 1873-4936 VL - 731 SP - 344 EP - 350 PB - Elsevier CY - Amsterdam AN - OPUS4-45255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Bode, Johannes A1 - Cabeza, Sandra T1 - Influence of deposition hatch length on residual stress in selective laser melted Inconel 718 N2 - The present study aims to evaluate the bulk residual stresses in SLM parts by using neutron diffraction measurements performed at E3 line -BER II neutron reactor- of Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. Together with microstructure characterization and distortion measurements, it is possible to describe the stress state throughout the whole sample. The sample was measured in as-build condition (on a build plate) and after releasing from the build plate. The used material is the nickel based superalloy 718. This alloy is widely used in aerospace and chemical industries due to its superior corrosion and heat resistant properties. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component. The normal and transversal component exhibits a rather compressive behavior while the longitudinal was tensile in the center part of the sample and became compressive towards the tip. As expected, the absolute values of all stress components decreased after releasing the sample from the building plate. A surface scan utilizing a coordinate-measuring machine (CMM) allowed us to present top surface distortion before and after releasing. The top surface showed a distortion around ±80µm after releasing. Microstructure evolution in the scanning-building cross-section is largely dominated by columnar grains. In addition, many small random orientated grains are prominent in the regions of a laser overlap during SLM. In summary, for the sample of superalloy 718 manufactured by SLM, a small distortion occurred when removing the sample from the build plate whereby the residual stress state decreases. Moreover, the observed columnar grains in the building direction could give a reason for the lowest stress values in that normal direction. However, the most important parameter controlling the residual stresses is the temperature gradient. Hence, future investigations are planned for a different scan strategy to distribute the laser impact in a more homogenous manner. T2 - WAM2018 CY - Grenoble, France DA - 09.04.2018 KW - Additive manufacturing KW - SLM KW - Residual stress KW - In718 PY - 2018 AN - OPUS4-44694 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni T1 - Starting new adventures at BAM. The focus area projects PROMOAM and AGIL N2 - While additive manufacturing (AM) is blossoming in nearly every industrial field, and the most different process are being used to produce components and materials, little attention is paid on the safety concerns around AM materials and processes. Leveraging on our leading expertise in non-destructive testing (NDT) and materials characterization, we approach AM at BAM under two important viewpoints: first the on-line monitoring of the process and of the product, second the evolution of the (unstable) microstructure of AM materials under external loads. These two subjects are the core of the two new-born internal projects ProMoAM and AGIL, respectively. A detailed view of the goals and the organization of these two projects will be given, together with the expected output, and some preliminary results. T2 - Vortragsveranstaltung Bauhaus Universität, im Rahmen der Kolloquien der Fakultät Bauwesen. CY - Weimar, Germany DA - 01.06.2018 KW - Thermography KW - Additive Manufacturing KW - Non-destructive testing KW - On-line monitoring KW - Residual stress PY - 2018 AN - OPUS4-45118 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Thiede, Tobias A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Klaus, Manuela A1 - Genzel, Christoph A1 - Haberland, Christoph A1 - Bruno, Giovanni T1 - The influence of the support structure on residual stress and distortion in SLM Inconel 718 parts N2 - The effect of support structure and of removal from the base plate on the residual stress state in selective laser melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after removal from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support, stress redistribution took place after removal from the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress-relieving heat treatments are still needed. KW - Additive manufacturing KW - SLM KW - Residual stress KW - Synchrotron X-ray diffraction KW - IN718 PY - 2018 U6 - https://doi.org/10.1007/s11661-018-4653-9 SN - 1073-5623 VL - 49A IS - 7 SP - 3038 EP - 3046 PB - Springer Sciences & Business Media CY - New York, NY AN - OPUS4-45100 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artzt, K. A1 - Mishurova, Tatiana A1 - Bauer, P.-P. A1 - Gussone, J. A1 - Barriobero-Vila, P. A1 - Evsevleev, Sergei A1 - Bruno, Giovanni A1 - Requena, G. A1 - Haubrich, J. T1 - Pandora’s Box–Influence of Contour Parameters on Roughness and Subsurface Residual Stresses in Laser Powder Bed Fusion of Ti-6Al-4V N2 - The contour scan strategies in laser powder bed fusion (LPBF) of Ti-6Al-4V were studied at the coupon level. These scan strategies determined the surface qualities and subsurface residual stresses. The correlations to these properties were identified for an optimization of the LPBF processing. The surface roughness and the residual stresses in build direction were linked: combining high laser power and high scan velocities with at least two contour lines substantially reduced the surface roughness, expressed by the arithmetic mean height, from values as high as 30 μm to 13 μm, while the residual stresses rose from ~340 to about 800 MPa. At this stress level, manufactured rocket fuel injector components evidenced macroscopic cracking. A scan strategy completing the contour region at 100 W and 1050 mm/s is recommended as a compromise between residual stresses (625 MPa) and surface quality (14.2 μm). The LPBF builds were monitored with an in-line twin-photodiode-based melt pool monitoring (MPM) system, which revealed a correlation between the intensity quotient I2/I1, the surface roughness, and the residual stresses. Thus, this MPM system can provide a predictive estimate of the surface quality of the samples and resulting residual stresses in the material generated during LPBF. KW - Additive manufacturing KW - Ti-6Al-4V KW - Contour scan strategy KW - Surface roughness KW - Melt pool monitoring KW - Residual stress KW - Synchrotron X-ray diffraction PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-510585 VL - 13 IS - 15 SP - 3348 AN - OPUS4-51058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Sydow, B. A1 - Thiede, Tobias A1 - Sizova, I. A1 - Ulbricht, Alexander A1 - Bambach, M. A1 - Bruno, Giovanni T1 - Residual Stress and Microstructure of a Ti-6Al-4V Wire Arc Additive Manufacturing Hybrid Demonstrator N2 - Wire Arc Additive Manufacturing (WAAM) features high deposition rates and, thus, allows production of large components that are relevant for aerospace applications. However, a lot of aerospace parts are currently produced by forging or machining alone to ensure fast production and to obtain good mechanical properties; the use of these conventional process routes causes high tooling and material costs. A hybrid approach (a combination of forging and WAAM) allows making production more efficient. In this fashion, further structural or functional features can be built in any direction without using additional tools for every part. By using a combination of forging basic geometries with one tool set and adding the functional features by means of WAAM, the tool costs and material waste can be reduced compared to either completely forged or machined parts. One of the factors influencing the structural integrity of additively manufactured parts are (high) residual stresses, generated during the build process. In this study, the triaxial residual stress profiles in a hybrid WAAM part are reported, as determined by neutron diffraction. The analysis is complemented by microstructural investigations, showing a gradient of microstructure (shape and size of grains) along the part height. The highest residual stresses were found in the transition Zone (between WAAM and forged part). The total stress range showed to be lower than expected for WAAM components. This could be explained by the thermal history of the component. KW - Additive manufacturing KW - Neutron diffraction KW - Residual stress KW - Hybrid manufacturing KW - WAAM KW - Ti-6Al-4V PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-508245 VL - 10 IS - 6 SP - 701 PB - MDPI AN - OPUS4-50824 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hensel, J. A1 - Kromm, Arne A1 - Nitschke-Pagel, T. A1 - Dixneit, Jonny A1 - Dilger, K. T1 - Capability of martensitic low transformation temperature welding consumables for increasing the fatigue strength of high strength steel joints N2 - The use of low transformation temperature (LTT) filler materials represents a smart approach for increasing the fatigue strength of welded high strength steel structures apart from the usual procedures of post weld treatment. The main mechanism is based on the effect of the low start temperature of martensite formation on the stress already present during welding. Thus, compressive residual stress formed due to constrained volume expansion in connection with phase transformation become highly effective. Furthermore, the weld metal has a high hardness that can delay the formation of fatigue cracks but also leads to low toughness. Fundamental investigations on the weldability of an LTT filler material are presented in this work, including the characterization of the weld microstructure, its hardness, phase transformation temperature and mechanical properties. Special attention was applied to avoid imperfections in order to ensure a high weld quality for subsequent fatigue testing. Fatigue tests were conducted on the welded joints of the base materials S355J2 and S960QL using conventional filler materials as a comparison to the LTT filler. Butt joints were used with a variation in the weld type (DY-weld and V-weld). In addition, a component-like specimen (longitudinal stiffener) was investigated where the LTT filler material was applied as an additional layer. The joints were characterized with respect to residual stress, its stability during cyclic loading and microstructure. The results show that the application of LTT consumables leads to a significant increase in fatigue strength when basic design guidelines are followed. This enables a benefit from the lightweight design potential of high-strength steel grades. KW - Low transformation temperature KW - Welding KW - Fatigue strength KW - Residual stress PY - 2020 U6 - https://doi.org/10.3139/120.111562 VL - 62 IS - 9 SP - 891 EP - 899 PB - Carl Hanser Verlag AN - OPUS4-51180 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Burbank, John A1 - Woydt, Mathias T1 - Optimization of pre-conditioned cold work hardening of steel alloys for friction and wear reductions under slip-rolling contact N2 - The goal of reducing CO2 emissions in the automobile industry has led to the development of increasingly efficient lightweight material solutions that yield enhanced performance. In light of this goal, this current work involves the optimization of the pre-conditioning of novel, high toughness steel bearings without thermo-chemical treatment, with the aim of transferring the running-in phase into the final step of the mechanical finishing process. A case-hardened gear steel and two novel non-case-hardened steels were evaluated. KW - Work hardening KW - Steel KW - Gear KW - Bearing KW - Residual stress KW - Hardness PY - 2016 U6 - https://doi.org/10.1016/j.wear.2016.01.011 SN - 0043-1648 VL - 350-351 SP - 141 EP - 154 PB - Elsevier B.V. CY - Amsterdam, u.a. AN - OPUS4-35665 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Evsevleev, Sergei A1 - Sevostianov, I. A1 - Mishurova, Tatiana A1 - Hofmann, M. A1 - Garcés, G. A1 - Bruno, Giovanni T1 - Explaining Deviatoric Residual Stresses in Aluminum Matrix Composites with Complex Microstructure N2 - The residual stresses in multiphase metal Matrix composites with both random planar-oriented short fibers and particles were studied by neutron diffraction and by a model based on the reformulation of classic Maxwell’s homogenization method. Contrary to common understanding and state-of-the-art models, we experimentally observed that randomly oriented phases possess non-hydrostatic residual stress. The recently developed modeling Approach allows calculating the residual stress in all phases of the composites. It rationalizes the presence of deviatoric stresses Accounting for the interaction of random oriented phases with fibers having preferential orientation. KW - Metal matrix composite KW - Residual stress KW - Deviatoric KW - Micromechanics PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-506472 VL - 51 IS - 6 SP - 3104 EP - 3113 PB - Springer AN - OPUS4-50647 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, K. A1 - Haubrich, J. A1 - Requena, G. A1 - Bruno, Giovanni T1 - New aspects about the search for the most relevant parameters optimizing SLM materials N2 - Using non-optimum combination of manufacturing parameters in selective laser melting (SLM) may lead to reduction of quality of component: defects generation, distortion of geometry and even cracking. Usually, the optimization of parameters is performed by changing volumetric energy density (Ev) and selecting parameters giving low porosity values. However, not only low porosity but also stable microstructure and low residual stresses will help to achieve advanced mechanical behavior of the component. In present work, we investigated cuboid-shaped Ti-6Al-4V samples produced with different manufacturing parameters. The parameters leading to the same Ev were considered as well as parameters which are not included in Ev. Residual stresses in subsurface region were investigated by synchrotron X-ray diffraction, which allows to penetrate around 100 µm from the surface therefore overcome the problem of high roughness of SLM components without additional sample preparation. Only tensile stresses were found along the building direction, that can play critical role especially during cyclic loading. The pore shape and spatial distribution obtained by computed tomography varied for samples produced with the same Ev. However, by using some process parameters it was possible to decrease residual stresses and obtain uniform α+β Ti microstructure and relatively low porosity. Additionally, it was found that not included in Ev (e.g., base plate position, focus distance) should be considered as additional manufacturing parameters during SLM process. T2 - ESIAM 2019 CY - Trondheim, Norway DA - 09.09.2019 KW - Additive manufacturing KW - Computed tomography KW - Residual stress PY - 2019 AN - OPUS4-49216 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Lausch, T. T1 - Issues and challenges in component welding of high strength fine-grained structural steels N2 - When assessing the performance of welded components residual stresses are vital. The possibilities of transferring the real boundary conditions of welding, which influence the residual stress, into the laboratory are highlighted in this contribution. The potentials of a test system specially developed for this purpose are demonstrated. The component design induces global process-, geometry- and material-dependent stresses, which can be simulated and quantified in the system. In addition, the resulting local residual stress distribution can be exactly determined with high spatial resolution with the aid of X-ray diffraction. Examples are presented of how the conditions to be found during production are simulated in the laboratory. T2 - AJP 2019 CY - Ponta Delgada, Azores (Portugal) DA - 24.10.2019 KW - Residual stress KW - Welding KW - X-ray diffraction KW - Creep-resistant steel KW - Large-scale test PY - 2019 AN - OPUS4-50036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Bruno, Giovanni A1 - Sprengel, Maximilian A1 - Madia, Mauro A1 - Kromm, Arne T1 - Residual stresses in Laser Beam Melting (LBM) – Critical Review and outlook of activities at BAM N2 - Additive manufacturing (AM) technologies have experienced an exceedingly rapid growth, which is coupled with the knowledge about the resulting material properties and performance. In particular, residual stress (RS) was soon recognized as an important issue in AM parts, such that parts are usually subjected to a post build-heat-treated. Significant effort has been spent on simulations of RS in AM, especially using finite element methods. As a consequence, the experimental determination of RS has thereby become increasingly important as a validation tool for simulations, as well as a method for assessing the influence of process parameters. In particular, diffraction methods, which are fundamentally non-destructive, offer enormous possibilities to gain knowledge on the residual stress state in real components, since synchrotron radiation and neutrons can penetrate even heavy metals up to several millimeters or centimeters, respectively. Indeed, significant progress has been achieved, in the understanding of the origins of the RS fields as a function of process parameters, as well as their stability under thermal and/or mechanical exposure. In this paper, a few success stories will be outlined. It will be shown how the determination of RS in metallic parts (with the focus on those produced by laser powder bed fusion) has even revealed that process parameters that were previously considered unimportant (e.g. the position and orientation on the base plate) play a major role in the onset of residual stress accumulation. However, while RS characterization is starting to be considered in the component design, deposition strategy (e.g. build plate temperature), and even in the definition of the relevant metric to assess the quality of a part, much is still to be investigates about the hypotheses underlying its experimental determination. Therefore, some aspects to be aware of, or even those which to date are unclear, will also be discussed. These include the determination of the stress-free reference and of the principal axes of stress. All of these aspects will lead towards a comprehensive understanding of the process-structure-performance relationships in AM materials and parts. T2 - Fourth ASTM Symposium on Structural Integrity of Additive Manufactured Materials and Parts CY - Gaylord National Resort And Convention Center; National Harbor, MD DA - 07.10.2019 KW - Diffraction KW - Additive Manufacturing KW - Residual stress PY - 2019 AN - OPUS4-49367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yu, C.-H. A1 - Peng, R. L. A1 - Luzin, V. A1 - Sprengel, Maximilian A1 - Calmunger, M. A1 - Lundgren, J.-E. A1 - Brodin, H. A1 - Kromm, Arne A1 - Moverare, J. T1 - Thin-wall effects and anisotropic deformation mechanisms of an additively manufactured Ni-based superalloy N2 - Laser powder bed fusion (LPBF) of Ni-based superalloys shows great potential for high temperature applications, for example, as a burner repair application for gas turbines where the thin-walled structure is important. It motivates this work to investigate the evolution of microstructure and the anisotropic mechanical behavior when plate-like specimens are built with a thickness from 4 mm down to 1 mm. By performing texture analysis using neutron diffraction, a clear transition in fiber texture from <011> to <001> is indicated when the specimen becomes thinner. The residual stress shows no thickness dependence, and at the subsurface the residual stress reaches the same level as the yield strength. Due to the rough as-built surface, a roughness compensation method for mechanical properties of thin-walled structures is outlined and demonstrated. Tensile tests from room temperature up to 700 ◦C have been carried out. Anisotropic mechanical behavior is found at all temperatures, which is strongly related to the anisotropic texture evolution. Stronger texture evolution and grain rotations are discovered when the tensile loading is applied along the building direction. The mechanical behavior has been compared to a wrought material, where the high dislocation density and the subgrain structure of the LPBF material result in a higher yield strength. Combining the statistical texture analysis by neutron diffraction with mechanical testing, EBSD grain orientation mapping and the investigation of dislocation structures using transmission electron microscopy, this work illustrates the significance of texture for the thin-wall effect and anisotropic mechanical behavior of LPBF materials. KW - Hastelloy X KW - Hot tensile test KW - Crystallographic texture KW - Roughness KW - Residual stress KW - Dislocation density PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-518759 VL - 36 SP - 101672 PB - Elsevier B.V. AN - OPUS4-51875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander A1 - Altenburg, Simon A1 - Sprengel, Maximilian A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Fritsch, Tobias A1 - Mishurova, Tatiana A1 - Serrano Munoz, Itziar A1 - Evans, Alexander A1 - Hofmann, Michael A1 - Bruno, Giovanni T1 - Separation of the Formation Mechanisms of Residual Stresses in LPBF 316L N2 - Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured parts and important factors for the residual stress formation. This study examined the influence of heat accumulation on the distribution of residual stress in two prisms produced by Laser Powder Bed Fusion (LPBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two different border fill scan strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. The goal was to reveal the effect of different heat inputs on samples featuring the same solidification shrinkage. Residual stress was characterised in one plane perpendicular to the building direction at the mid height using Neutron and Lab X-ray diffraction. Thermography data obtained during the build process were analysed in order to correlate the cooling rates and apparent surface temperatures with the residual stress results. Optical microscopy and micro computed tomography were used to correlate defect populations with the residual stress distribution. The two scanning strategies led to residual stress distributions that were typical for additively manufactured components: compressive stresses in the bulk and tensile stresses at the surface. However, due to the different heat accumulation, the maximum residual stress levels differed. We concluded that solidification shrinkage plays a major role in determining the shape of the residual stress distribution, while the temperature gradient mechanism appears to determine the magnitude of peak residual stresses. T2 - MLZ User Meeting 2020 CY - Online meeting DA - 08.12.2020 KW - Computed tomography KW - Neutron diffraction KW - X-ray diffraction KW - Additive manufacturing KW - Residual stress KW - Thermography KW - LPBF KW - Laser Powder Bed Fusion PY - 2020 AN - OPUS4-51793 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro A1 - Bruno, Giovanni A1 - Evans, Alexander A1 - Sprengel, Maximilian A1 - Kromm, Arne T1 - Residual stresses in Laser Beam Melting (LBM) – Critical Review and outlook of activities at BAM N2 - Additive manufacturing (AM) technologies have experienced an exceedingly rapid growth, which is coupled with the knowledge about the resulting material properties and performance. In particular, residual stress (RS) was soon recognized as an important issue in AM parts, such that parts are usually subjected to a post build-heat-treated. Significant effort has been spent on simulations of RS in AM, especially using finite element methods. As a consequence, the experimental determination of RS has thereby become increasingly important as a validation tool for simulations, as well as a method for assessing the influence of process parameters. In particular, diffraction methods, which are fundamentally non-destructive, offer enormous possibilities to gain knowledge on the residual stress state in real components, since synchrotron radiation and neutrons can penetrate even heavy metals up to several millimeters or centimeters, respectively. Indeed, significant progress has been achieved, in the understanding of the origins of the RS fields as a function of process parameters, as well as their stability under thermal and/or mechanical exposure. In this paper, a few success stories will be outlined. It will be shown how the determination of RS in metallic parts (with the focus on those produced by laser powder bed fusion) has even revealed that process parameters that were previously considered unimportant (e.g. the position and orientation on the base plate) play a major role in the onset of residual stress accumulation. However, while RS characterization is starting to be considered in the component design, deposition strategy (e.g. build plate temperature), and even in the definition of the relevant metric to assess the quality of a part, much is still to be investigates about the hypotheses underlying its experimental determination. Therefore, some aspects to be aware of, or even those which to date are unclear, will also be discussed. These include the determination of the stress-free reference and of the principal axes of stress. All of these aspects will lead towards a comprehensive understanding of the process-structure-performance relationships in AM materials and parts. T2 - Fourth ASTM Symposium on Structural Integrity of Additive Manufactured Materials and Parts CY - Gaylord National Resort And Convention Center; National Harbor, MD, USA DA - 07.10.2019 KW - Residual stress KW - Additive Manufacturing KW - Diffraction PY - 2019 AN - OPUS4-49822 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Kromm, Arne A1 - Cabeza, Sandra A1 - Serrano Munoz, Itziar A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Bruno, Giovanni T1 - Residual stresses in am review and oulook of activities at BAM N2 - Critical discussion of residual stress Analysis in additive manufacturing from examples in literature and an overview of activities at BAM T2 - Workshop on Fatigue of Additive Manufactured Metallic Components CY - BAM, Berlin, Germany DA - 16.05.2019 KW - Diffraction KW - Additive Manufacturing KW - Residual stress PY - 2019 AN - OPUS4-49843 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander A1 - Altenburg, Simon A1 - Sprengel, Maximilian A1 - Thiede, Tobias A1 - Serrano Munoz, Itziar A1 - Mishurova, Tatiana A1 - Mohr, Gunther A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - How Temperature Gradient Influences the Formation of Residual Stresses in Metallic Parts Made by L-PBF N2 - Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured (AM) parts and important factors for residual stress formation which have implications on structural integrity. This study examined the influence of heat input on the distribution of residual stresses in two prisms produced by laser powder bed fusion (L-PBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two distinct helix scanning strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. Residual stresses were characterised at one plane perpendicular to the building direction at half of its build height using neutron diffraction. In addition, the defect distribution was analysed via micro X-ray computed tomography (µCT) in a twin specimen. Both scanning strategies reveal residual stress distributions typical for AM: compressive stresses in the bulk and tensile stresses at the surface. However, temperature gradients and maximum stress levels differ due to the different heat input. Regarding the X-ray µCT results, they show an accumulation of defects at the corners where the laser direction turned through 90°. The results demonstrate that neutron diffraction and X-ray µCT can be successfully used as non-destructive methods to analyse through-thickness residual stress and defect distribution in AM parts, and in the presented case, illustrate the influence of scanning strategies. This approach contributes to deeper assessment of structural integrity of AM materials and components. T2 - First European Conference on Structural Integrity of Additively Manufactured Materials (ESIAM19) CY - Trondheim, Norwegen DA - 09.09.2019 KW - AGIL KW - Neutron diffraction KW - Thermography KW - Additive manufacturing KW - Residual stress PY - 2019 AN - OPUS4-49805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Online-Observation of Martensite Formation by combined use of Synchrotron Diffraction and Dilatometry N2 - Welding residual stress engineering by means of an adjusted martensite phase transformation would be highly attractive as detrimental tensile residual stresses may be prevented already during welding without time and cost intensive post processing. The present study shows a synchrotron diffraction analysis of a martensitic steel subjected to thermo-mechanical load cycles. Experiments were conducted regarding the microstructural strain response during the austenite to martensite transformation. The strains are a function of the temperature and the specific loads applied during cooling. The relation between the transformation plasticity of the material, the amount of martensite formed and the arising strains can thus be assessed. The lattice plane specific strains were compared to experimental findings from (macro) dilatation tests. It is shown that the microscopic material behavior differs remarkably from the one observed on the macroscopic scale, what leads to characteristic residual stresses in the material. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Martensite KW - Synchrotron KW - Dilatometry KW - Residual stress KW - Phase transformation PY - 2019 SP - 83 EP - 84 PB - SEIEI Printing Co., Ltd CY - Osaka, Japan AN - OPUS4-49770 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schroepfer, Dirk A1 - Hannemann, Andreas T1 - In-situ Observation of Stress Evolution and Cracking during High Strength Steel Welding N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system with a load capacity of 2 MN specifically developed for online monitoring of stress formation and cracking are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be quantified in-situ during welding and post weld heat treatment. Examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. Elevated working temperatures significantly increase the tensile residual stresses in the heat affected zone (HAZ). The effect of mechanical stresses resulting from welding on stress relief cracking is demonstrated by the example of a creep resistant steel. Reheat cracks were monitored online during post weld heat treatment. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Residual stress KW - Restraint KW - Welding KW - Large-scale test KW - Reheat cracking PY - 2019 SP - 83 EP - 84 PB - SEIEI Printing Co., Ltd CY - Osaka, Japan AN - OPUS4-49773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schroepfer, Dirk T1 - In-situ Observation of Stress Evolution during High Strength Steel Welding N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system with a load capacity of 2 MN specifically developed for online monitoring of stress formation and cracking are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be quantified in-situ during welding and post weld heat treatment. Examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. Elevated working temperatures significantly increase the tensile residual stresses in the heat affected zone (HAZ). The effect of mechanical stresses resulting from welding on stress relief cracking is demonstrated by the example of a creep resistant steel. Reheat cracks were monitored online during post weld heat treatment. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Residual stress KW - Restraint KW - Welding KW - Large-scale test KW - Reheat cracking PY - 2019 AN - OPUS4-49763 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Online-Observation of Martensite Formation by combined use of Synchrotron Diffraction and Dilatometry N2 - Welding residual stress engineering by means of an adjusted martensite phase transformation would be highly attractive as detrimental tensile residual stresses may be prevented already during welding without time and cost intensive post processing. The present study shows a synchrotron diffraction analysis of a martensitic steel subjected to thermo-mechanical load cycles. Experiments were conducted regarding the microstructural strain response during the austenite to martensite transformation. The strains are a function of the temperature and the specific loads applied during cooling. The relation between the transformation plasticity of the material, the amount of martensite formed and the arising strains can thus be assessed. The lattice plane specific strains were compared to experimental findings from (macro) dilatation tests. It is shown that the microscopic material behavior differs remarkably from the one observed on the macroscopic scale, what leads to characteristic residual stresses in the material. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Martensite KW - Synchrotron KW - Dilatometry KW - Residual stress KW - Phase transformation PY - 2019 AN - OPUS4-49768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Cabeza, S. A1 - Nadammal, Naresh A1 - Bode, Johannes A1 - Kromm, Arne A1 - Haberland, C. A1 - Bruno, Giovanni T1 - Influence of deposition hatch length on residual stress in selective laser melted Inconel 718 N2 - Additive Manufacturing (AM) by Selective Laser Melting (SLM) offers ample scope for producing geometrically complex parts in comparison to the traditional subtractive manufacturing strategies. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. The present study aims to evaluate the bulk residual stresses in SLM parts by using neutron diffraction measurements performed at E3 line -BER II neutron reactor- of Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. Together with microstructure characterization and distortion measurements, it is possible to describe the stress state throughout the whole sample. The sample was measured in as-build condition (on a build plate) and after releasing from the build plate. The used material is the nickel based superalloy 718. This alloy is widely used in aerospace and chemical industries due to its superior corrosion and heat resistant properties. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component. The normal and transversal component exhibits a rather compressive behavior while the longitudinal was tensile in the center part of the sample and became compressive towards the tip. As expected, the absolute values of all stress components decreased after releasing the sample from the building plate. A surface scan utilizing a coordinate-measuring machine (CMM) allowed us to present top surface distortion before and after releasing. The top surface showed a distortion around ±80µm after releasing. Microstructure evolution in the scanning-building cross-section is largely dominated by columnar grains. In addition, many small random orientated grains are prominent in the regions of a laser overlap during SLM. In summary, for the sample of superalloy 718 manufactured by SLM, a small distortion occurred when removing the sample from the build plate whereby the residual stress state decreases. Moreover, the observed columnar grains in the building direction could give a reason for the lowest stress values in that normal direction. However, the most important parameter controlling the residual stresses is the temperature gradient. Hence, future investigations are planned for a different scan strategy to distribute the laser impact in a more homogenous manner. T2 - HZB User Meeting 2017 CY - Berlin, Germany DA - 15.12.2017 KW - AM KW - SLM KW - IN 718 KW - Neutron diffraction KW - Residual stress KW - Hatch length KW - Microstructure PY - 2017 AN - OPUS4-43475 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, Katia A1 - Haubrich, Jan A1 - Bruno, Giovanni A1 - Requena, Guillermo T1 - An assessment of subsurface residual stress in Selective Laser Melted Ti-6Al-4V parts N2 - In the present study, Ti-6Al-4V bridge-like specimens were manufactured additively by selective laser melting (SLM) under different laser scanning speed conditions in order to compare the effect of process energy density on the residual stress state. Subsurface residual stress analysis was conducted by means of synchrotron diffraction in energy dispersive mode for three conditions: as-built on base plate, released from base plate, and after heat treatment on the base plate. The quantitative residual stress characterization shows a correlation with the qualitative bridge curvature method. Computed tomography (CT) was carried out to ensure that no stress relief took place owing to the presence of porosity. CT allows obtaining spatial and size pores distribution which helps in optimization of the SLM process. High tensile residual stresses were found at the lateral surface for samples in the as-built conditions. We observed that higher laser energy density during fabrication leads to lower residual stresses. Samples in released condition showed redistribution of the stresses due to distortion. A method for the calculation of the stress associated to distortion of the parts after cutting from base plate is proposed. The distortion measurements were used as input for FEM simulations. T2 - Symposium Zerstörungsfreie Materialcharakterisierung. Charakterisierung additiv gefertigter Komponenten CY - Berlin, Germany DA - 28.11.2017 KW - Additive manufacturing KW - Selective laser melting KW - Residual stress KW - Synchrotron X-ray diffraction PY - 2017 AN - OPUS4-43214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Carstensen, J. A1 - Bergmann, L. A1 - dos Santos, J. F. A1 - Wu, C. S. A1 - Rethmeier, Michael T1 - Numerical simulation of thermally induced residual stresses in friction stir welding of aluminum alloy 2024-T3 at different welding speeds N2 - The paper deals with a numerical finite element simulation of the residual stress evolution in friction stir welding of 6 mm thick aluminum alloy AA2024-T3. The transient thermal field during the welding process was calculated with the commercial code COMSOL Multiphysics 5.0. Therefore, a thermal-pseudo-mechanical (TPM) heat source was implemented. A subsequent mechanical simulation was performed with varying hardening models for different welding speeds of 60 and 300 mm/min. The influence of softening of the material, which was due to hardening precipitation dissolution associated to the heating, was also investigated. Experiments in terms of thermocouple measurements as well as Vickers hardness and X-ray measurements of the residual stresses were conducted and compared to numerically obtained results. A qualitatively as well as quantitatively good agreement was found for different applied welding speeds. KW - Friction stir welding KW - Residual stress KW - Finite element simulation KW - Thermal softening KW - Aluminum alloy 2024-T3 PY - 2017 U6 - https://doi.org/10.1007/s00170-016-9793-8 SN - 0268-3768 SN - 1433-3015 VL - 91 SP - 1443 EP - 1452 PB - Springer CY - London AN - OPUS4-40511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Pelkner, Matthias A1 - Lyamkin, Viktor A1 - Sonntag, Nadja A1 - Bruno, Giovanni A1 - Skrotzki, Birgit A1 - Kreutzbruck, Marc T1 - Evaluation of high spatial resolution imaging of magnetic stray fields for early damage detection N2 - The paper discusses the evaluation of elastic and plastic strain states in two low-carbon steels of the same steel group with high spatial resolution GMR (giant magneto resistance) sensors. The residual stress distributions of tungsten inert gas welded plates were determined by means of neutron diffraction as a reference. The normal component of local residual magnetic stray fields arise in the vicinity of the positions of maximum stress. The experiments performed on flat tensile specimen indicate that the boundaries of plastic deformations are a source of stray fields. The spatial variations of magnetic stray fields for both the weld and the tensile samples are in the order of the earths magnetic field. T2 - 43rd Annual Review of Progress in Quantitative Nondestructive Evaluation, Volume 36 CY - Atlanta, Georgia, USA DA - 17.07.2016 KW - Plastic deformation KW - GMR KW - Neutron diffraction KW - Residual stress KW - Microstructure KW - Low carbon steel KW - TIG weld PY - 2017 SN - 978-0-7354-1474-7 U6 - https://doi.org/10.1063/1.4974688 SN - 0094-243X VL - 1806 IS - 1 SP - Article UNSP 110010-1 EP - 10 PB - AIP Publishing CY - Melville, NY 11747 AN - OPUS4-39279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Artzt, Katia A1 - Haubrich, J. A1 - Klaus, M. A1 - Genzel, Ch. A1 - Requena, G. A1 - Bruno, Giovanni T1 - An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V N2 - Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. KW - Selective laser melting KW - Additive manufacturing KW - Heat treatment KW - Ti-6Al-4V KW - Synchrotron X-ray diffraction KW - Residual stress PY - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-395759 SN - 1996-1944 VL - 10 IS - 4 SP - Article 348, 1 EP - 14 AN - OPUS4-39575 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schröpfer, Dirk A1 - Dixneit, Jonny A1 - Hannemann, Andreas A1 - Kannengießer, Thomas ED - Neu, Richard W. ED - Totten, George E. T1 - From the field to the lab: Real scale assessment of stresses in welded components N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system specifically developed for this purpose with a maximum capacity of 2 MN are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be simulated and quantified within the system. Additionally, X-ray diffraction can be applied to determine the resulting local residual stress distribution precisely with high spatial resolution. Two examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. It was possible to clarify why elevated working temperatures significantly increase the bending stresses in the welded joint and therefore the tensile residual stresses in the heat affected zone (HAZ). The effect of a heat treatment applied under mechanical stress resulting from welding is demonstrated by the example of a creep resistant steel. Reheat cracking is significantly increased in this case compared to small scale laboratory based tests. KW - Residual stress KW - Welding KW - Large-scale test KW - Creep resistant steel KW - High strength steel PY - 2018 U6 - https://doi.org/10.1520/MPC20170111 SN - 2379-1365 VL - 7 IS - 4 SP - 574 EP - 593 PB - ASTM International CY - West Conchohocken AN - OPUS4-46662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Cabeza, S. A1 - Kuntner, M. A1 - Mishurova, Tatiana A1 - Klaus, M. A1 - Kling e Silva, L. A1 - Skrotzki, Birgit A1 - Genzel, Ch. A1 - Bruno, Giovanni T1 - Visualisation of deformation gradients in structural steel by macroscopic magnetic domain distribution imaging (Bitter technique) N2 - Abstract While classically used to visualise the magnetic microstructure of functional materials (e.g., for magnetic applications), in this study, the Bitter technique was applied for the first time to visualise macroscopic deformation gradients in a polycrystalline low-carbon steel. Spherical indentation was chosen to produce a multiaxial elastic–plastic deformation state. After removing the residual imprint, the Bitter technique was applied, and macroscopic contrast differences were captured in optical microscopy. To verify this novel characterisation technique, characteristic “hemispherical” deformation zones evolving during indentation were identified using an analytical model from the field of contact mechanics. In addition, near-surface residual stresses were determined experimentally using synchrotron radiation diffraction. It is established that the magnetic domain distribution contrast provides deformation-related information: regions of different domain wall densities correspond to different “hemispherical” deformation zones (i.e., to hydrostatic core, plastic zone and elastic zone, respectively). Moreover, the transitions between these three zones correlate with characteristic features of the residual stress profiles (sign changes in the radial and local extrema in the hoop stress). These results indicate the potential of magnetic domain distribution imaging: visualising macroscopic deformation gradients in fine-grained ferromagnetic material with a significantly improved spatial resolution as compared to integral, mean value-based measurement methods. KW - Bitter technique KW - Deformation KW - Expanding cavity model KW - Indentation KW - Magnetic domain distribution KW - Residual stress PY - 2018 U6 - https://doi.org/10.1111/str.12296 SN - 1475-1305 VL - 54 IS - 6 SP - e12296, 1 EP - 15 PB - Wiley AN - OPUS4-46569 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Hannemann, Andreas A1 - Kannengießer, Thomas ED - Seefeldt, Marc T1 - In-situ determination of critical welding stresses during assembly of thick-walled components made of high-strength steel N2 - The performance and safety of welded high-strength low-alloyed steel (HSLA) components are substantially affected by the stresses occurring during and after welding fabrication, especially if welding shrinkage and distortion are severely restrained. The surrounding structure of the whole component affects loads in the far-field superimposing with welding stresses in the near-field of the weld. In this study a unique testing facility was used to restrain shrinkage and bending while analyse multiaxial far-field loads (max. 2 MN) during assembly of thick-walled component. A novel approach for the assessment of the in-situ-measured far-field data in combination with the actual weld geometry was elaborated. For the first time, analyses of the global bending moments of restrained welds based on the neutral axis of the actual weld load bearing section were achieved. Hence, far-field measurements offered the possibility to determine critical near-field stresses of the weld crosssections for the entire joining process. This work presents the approach for far-to-near field in-situ determination of stresses in detail for the 2-MN-testing system based on an extensive experimental work on HSLA steel welds, which demonstrates sources and consequences of these high local welding stresses. Thus, it was clarified, why the first weld beads are crucial regarding welding stresses and cold cracking, which is well known, but has never been measured so far. Accompanying analyses using X-ray diffraction (XRD) after welding show effects on local residual stress distributions. These analyses indicated viable prospects for stress reduction during assembly of thick-walled HSLA steel components. T2 - European Conference on Residual Stresses 2018 - ECRS-10 CY - Leuven, Belgium DA - 11.09.2018 KW - Residual stress KW - Welding KW - Large-scale test KW - X-ray diffraction KW - HSLA steel PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-466053 SN - 978-1-9452-9188-3 SN - 978-1-9452-9189-0 SN - 2474-395X SN - 2474-3941 VL - 6 SP - 191 EP - 196 PB - Materials Research Forum LLC CY - Millersville, PA, USA AN - OPUS4-46605 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Hannemann, Andreas A1 - Kannengießer, Thomas T1 - In-situ determination of critical welding stresses during assembly of thick-walled components made of high-strength steel N2 - The performance and safety of welded high-strength low-alloyed steel (HSLA) components are substantially affected by the stresses occurring during and after welding fabrication, especially if welding shrinkage and distortion are severely restrained. The surrounding structure of the whole component affects loads in the far-field superimposing with welding stresses in the near-field of the weld. In this study a unique testing facility was used to restrain shrinkage and bending while analyse multiaxial far-field loads (max. 2 MN) during assembly of thick-walled component. A novel approach for the assessment of the in-situ-measured far-field data in combination with the actual weld geometry was elaborated. For the first time, analyses of the global bending moments of restrained welds based on the neutral axis of the actual weld load bearing section were achieved. Hence, far-field measurements offered the possibility to determine critical near-field stresses of the weld crosssections for the entire joining process. This work presents the approach for far-to-near field in-situ determination of stresses in detail for the 2-MN-testing system based on an extensive experimental work on HSLA steel welds, which demonstrates sources and consequences of these high local welding stresses. Thus, it was clarified, why the first weld beads are crucial regarding welding stresses and cold cracking, which is well known, but has never been measured so far. Accompanying analyses using X-ray diffraction (XRD) after welding show effects on local residual stress distributions. These analyses indicated viable prospects for stress reduction during assembly of thick-walled HSLA steel components. T2 - European Conference on Residual Stresses 2018 - ECRS-10 CY - Leuven, Belgium DA - 11.09.2018 KW - Residual stress KW - Welding KW - Large-scale test KW - X-ray diffraction KW - HSLA steel PY - 2018 AN - OPUS4-46607 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Artzt, K. A1 - Haubrich, J. A1 - Requena, G. A1 - Bruno, Giovanni T1 - Exploring the correlation between subsurface residual stresses and manufacturing parameters in laser powder bed fused Ti-6Al-4V N2 - Subsurface residual stresses (RS) were investigated in Ti-6Al-4V cuboid samples by means of X-ray synchrotron diffraction. The samples were manufactured by laser powder bed fusion (LPBF) applying different processing parameters, not commonly considered in open literature, in order to assess their influence on RS state. While investigating the effect of process parameters used for the calculation of volumetric energy density (such as laser velocity, laser power and hatch distance), we observed that an increase of energy density led to a decrease of RS, although not to the same extent for every parameter variation. Additionally, the effect of support structure, sample roughness and LPBF machine effects potentially coming from Ar flow were studied. We observed no influence of support structure on subsurface RS while the orientation with respect to Ar flow showed to have an impact on RS.We conclude recommending monitoring such parameters to improve part reliability and reproducibility. KW - Additive manufacturing KW - Synchrotron X-ray diffraction KW - Residual stress KW - Ti-6Al-4V PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-474281 SN - 2075-4701 VL - 9 IS - 2 SP - 261, 1 EP - 13 PB - MDPI AN - OPUS4-47428 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vollert, J. A1 - Dixneit, Jonny A1 - Kromm, Arne A1 - Buslaps, Th. A1 - Kannengießer, Thomas T1 - In situ EDXRD study of MAG-welding using LTT weld filler materials under structural restraint N2 - Welding using low transformation temperature (LTT) filler materials is an innovative approach to mitigate detrimental welding residual stresses without cost-intensive post weldtreatments. Due to the local Generation of compressive residual stresses in the weld line by means of a delayed martensite transformation a significant enhancement of the cold cracking resistance of highly stressed welded components can be expected. For the effective usage of These materials a deeper understanding of the microstructural evolution inside the weld material is necessary to determine the complex processes that cause the residual stress formation during welding. Solid-state phase transformation kinetics and the evolution of strain in LTT weld filler materials are monitored in-situ at the instrument ID15A at the ESRF in Grenoble, France. The transferability to real components is implemented by using a realistic MAG welding process under consideration of structural restraint. During welding of multilayer joints, the phase Transformation and phase specific strain evolution of each individual layer is investigated in transmission geometry by means of energy-dispersive X-ray diffraction EDXRD using high energy synchrotron Radiation with a counting rate of 2.5 Hz. The measurement results of a 10% Cr / 10% Ni LTT weld filler are compared to data monitored for the conventional weld filler material G89. The in-situ data clearly indicate a strong effect on the local strain evolution and the formation of compressive strain. This results from the restraint volume expansion during the postponed austenite to martensite transformation of the LTT weld filler, which counteracts the thermal shrinkage. In contrast, for the conventional weld filler material the thermal contraction strains lead to tensile residual strain during welding. Furthermore, the results of in-situ observation during welding Show that the transformation kinetic is dependent on the welding sequence. KW - High energy synchrotron diffraction KW - Low transformation temperature KW - Weld filler KW - Residual stress KW - Welding PY - 2017 U6 - https://doi.org/10.4028/www.scientific.net/MSF.905.107 SN - 1662-9752 VL - 905 SP - 107 EP - 113 PB - Trans Tech Publications CY - Switzerland AN - OPUS4-41806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, Katia A1 - Haubrich, Jan A1 - Evans, Alexander A1 - Requana, Guillermo A1 - Bruno, Giovanni T1 - Influence of manufacturing parameters on microstructure and subsurface residual stress in SLM Ti-6Al-4V N2 - Residual stresses (RS) in SLM have a high impact on the chosen build strategy as well as on the mechanical performance of final product. RS are critical for the components since they can introduce distortion and cracking of the parts even during production. T2 - AAMS2018 CY - Sheffield, UK DA - 03.09.2018 KW - Residual stress KW - Selective laser melting KW - Synchrotron X-ray diffraction KW - Ti-6Al-4V PY - 2018 AN - OPUS4-45928 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Lausch, T. A1 - Dixneit, Jonny A1 - Hannemann, Andreas A1 - Kannengießer, Thomas T1 - From the Field to the Lab: Assessment of Residual Stresses in real-life Welded Components N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system specifically developed for this purpose with a maximum load capacity of 2 MN are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be simulated and quantified within the system. Additionally, X-ray diffraction can be applied to determine the resulting local residual stress distribution precisely with high spatial resolution. Examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. It was possible to clarify why elevated working temperatures significantly increase the tensile residual stresses in the heat affected zone (HAZ). The effect of a heat treatment applied under mechanical stress resulting from welding is demonstrated by the example of a creep resistant steel. Reheat cracking is significantly increased in this case compared to small scale laboratory based tests. T2 - European Conference on Residual Stresses - ECRS10 CY - Leuven, Belgium DA - 11.09.2018 KW - Welding KW - Residual stress KW - Large scale test PY - 2018 AN - OPUS4-45978 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Rhode, Michael A1 - Schröpfer, Dirk A1 - Steger, J. A1 - Lausch, T. A1 - Kannengießer, Thomas T1 - Residual stress Formation in component related stress relief cracking Tests of a welded creep resistant steel N2 - Submerged arc welded (SAW) components of creep-resistant low-alloyed Cr-Mo-V steels are used for thick-walled heavy petrochemical reactors (wall-thickness up to 475 mm) as well as employed in construction of modern high-efficient fossil fired power plants. These large components are accompanied by significant restraints during welding fabrication, especially at positions of different thicknesses like welding of nozzles. As a result, residual stresses occur, playing a dominant role concerning so-called stress relief cracking (SRC) typically during post weld heat treatment (PWHT). Besides specific metallurgical factors (like secondary hardening due to reprecipitation), high tensile residual stresses are a considerable influence factor on SRC. For the assessment of SRC susceptibility of certain materials mostly mechanical tests are applied which are isolated from the welding process. Conclusions regarding the influence of mechanical factors are rare so far. The present research follows an approach to reproduce loads, which occur during welding of real thick-walled components scaled to laboratory conditions by using Tests designed on different measures. A large-scale slit specimen giving a high restraint in 3 dimensions by high stiffness was compared to a medium-scale multi-pass welding U-Profile specimen showing a high degree of restraint in longitudinal direction and a small-scale TIG-remelted specimen. The small-scale specimens were additionally subjected to mechanical bending to induce loads that are found during fabrication on the real-scale in heavy components. Results show for all three cases comparable high tensile residual stresses up to yield strength with high gradients in the weld metal and the heat affected zone. Those high tensile stresses can be significant for cracking during further PWHT. T2 - European Conference on Residual Stresses - ECRS10 CY - Leuven, Belgium DA - 11.09.2018 KW - Welding KW - Residual stress KW - Creep resistant steel KW - Post weld heat treatment KW - Stress relief cracking KW - 13CrMoV9-10 PY - 2018 AN - OPUS4-45983 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Häberle, Nicolas A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Falkenberg, Rainer A1 - Kahlcke, Ole T1 - Application of multi-phase viscoplastic material modelling to computational welding mechanics of grade-s960ql steel N2 - The sound numerical prediction of welding-induced thermal stresses, residual stresses, and distortions strongly depends on the accurate description of a welded material’s thermomechanical deformation behaviour. In this work, we provide experimental data on the viscoplastic deformation behaviour of a grade-s960ql steel up to a temperature of 1000 ◦C. In addition, a multi-phase viscoplastic material model is proposed, which accounts for the experimentally observed isothermal deformation behaviour of grade-s960ql steel base and austenitised material, as well as for athermal contributions that originate from solid-state phase transformations. The multi-phase viscoplastic and a classic rateindependent isotropic hardening material model were applied in the numerical simulations of both-ends-fixed bar Satoh tests and a single-pass gas metal arc weld. The influence of material modelling choices on the agreement between numerical simulation and experimental results is discussed, and recommendations for further work are given. KW - Residual stress KW - Viscoplasticity KW - Material modeling KW - Grade S960QL steel PY - 2018 U6 - https://doi.org/10.1016/j.crme.2018.08.001 VL - 346 IS - 11 SP - 1018 EP - 1032 PB - Elsevier Masson SAS AN - OPUS4-46512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Cabeza, S. A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Haberland, C. A1 - Bode, Joannes T1 - An assessment of bulk residual stress in selective laser melted in 718 N2 - Having been introduced almost two decades ago, Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. The residual stress distribution in IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron (bulk) and laboratory X-ray (surface) diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-built condition (on a build plate) and after removal from the build plate. While surface stress fields seem constant for AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e. with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the baseplate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. We finally propose an explanation of those stress profiles based on the deposition strategy. T2 - ECRS10 CY - Leuven, Belgium DA - 09.09.2018 KW - Residual stress KW - Influence of rheology modifying admixtures on hydration of cementitious suspensions PY - 2018 AN - OPUS4-45997 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cabeza, Sandra A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Bruno, Giovanni T1 - Residual stress fields in AM Ni-718 in as built and after release from baseplate N2 - The residual stress distribution of IN718 parts produced by Selective Laser Melting (SLM) technique was studied by means of neutron diffraction. Two deposition hatching lengths were considered in the fabrication. Both lateral (building direction) and top (finishing) near-surface regions were characterized. Measurements on samples in as-built condition and after release from the plate proved the presence of stress gradients both in-plane and along the building direction. As-built samples presented in top region a longitudinal stress relief for large hatching, whereas small one showed tensile stresses around (200MPa) in the middle, evolving towards compression at the tip of the sample (down to -300MPa). Towards the lateral edge, longitudinal stresses shifted also to compression. The transverse stresses for large hatching were relief in the middle, whereas for small hatching shifted to compression at the edge. As for the normal component, this was more homogenous: stress-relief was proved for large hatching and, in contrast, was in compression (-200MPa) for small hatching. In the building direction (lateral region from base plate to top) of the sample with large hatching all stress components showed tensile values near the base plate (particularly high for normal component around 300MPa), decreasing towards compression to the top, where they were almost released. After release, in the top region, the longitudinal stress component for small hatching showed high compressive stresses in the central part (down to -250MPa). In contrast, for large hatching a stress relief was found. In the transversal direction, this behavior was inverted: a small hatching released stresses more effectively, while a large hatching presented high tensile stresses (around 200MPa). As for the normal component (i.e., building direction), the sample with small hatching was found in compression, while that with large hatching was stress-released or slightly in tension (around 100MPa). In the lateral surface region, all components showed similar behavior: a small hatching promoted high compressive stresses along the building direction, whereas a large hatching showed small tensile values at the bottom, which balance towards the top region. There is an overall shift of stresses in 3 directions towards tension when compared with as-built condition for top region. In contrast, the lateral region is stress-relief or shifted towards compression after cutting from baseplate. In conclusion, hatching length parameter strongly influenced the 3D distribution of residual stress in SLM produced parts. T2 - MECA SENS 2017 CY - Skukuza, South Africa DA - 19.09.2017 KW - Residual stress KW - Additive manufacturing KW - Selective laser melting KW - Neutron diffraction PY - 2017 AN - OPUS4-42033 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thiede, Tobias A1 - Cabeza, S. A1 - Mishurova, Tatiana A1 - Nadammal, N. A1 - Kromm, Arne A1 - Bode, Johannes A1 - Haberland, C. A1 - Bruno, Giovanni T1 - Residual stress in selective laser melted Inconel 718: Influence of the removal from base plate and deposition hatch length N2 - The residual stress distribution in IN718 elongated prisms produced by Selective Laser Melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed (RE) from the base plate were characterized. While surface stress fields seem constant for AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e. with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the baseplate. KW - Residual stress KW - Additive manufacturing KW - Neutron diffraction KW - Selective laser melting KW - Laboratory X-ray diffraction KW - Coordinate measurement machine KW - IN718 PY - 2018 U6 - https://doi.org/10.1520/MPC20170119 SN - 2379-1365 VL - 7 IS - 4 SP - 717 EP - 735 PB - ASTM International CY - USA, West Conshohocken AN - OPUS4-46673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Artzt, K. A1 - Haubrich, J. A1 - Requena, G. A1 - Bruno, Giovanni T1 - New aspects about the search for the most relevant parameters optimizing SLM materials N2 - While the volumetric energy density is commonly used to qualify a process parameter set, and to quantify its influence on the microstructure and performance of additively manufactured (AM) materials and components, it has been already shown that this description is by no means exhaustive. In this work, new aspects of the optimization of the selective laser melting process are investigated for AM Ti-6Al-4V. We focus on the amount of near-surface residual stress (RS), often blamed for the failure of components, and on the porosity characteristics (amount and spatial distribution). First, using synchrotron x-ray diffraction we show that higher RS in the subsurface region is generated if a lower energy density is used. Second, we show that laser de-focusing and sample positioning inside the build chamber also play an eminent role, and we quantify this influence. In parallel, using X-ray Computed Tomography, we observe that porosity is mainly concentrated in the contour region, except in the case where the laser speed is small. The low values of porosity (less than 1%) do not influence RS. KW - Additive manufacturing KW - Selective laser melting KW - Residual stress KW - Computed tomography PY - 2019 U6 - https://doi.org/10.1016/j.addma.2018.11.023 SN - 2214-8604 VL - 25 SP - 325 EP - 334 PB - Elsevier AN - OPUS4-46737 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Bruno, Giovanni T1 - BAM activities in material characterization by advanced X-ray imaging N2 - The overview of the activity of Federal Institute for Material Research and Testing (BAM, Belin, Germany) in the field of additively manufacturing material characterization will be presented. The research of our group is focused on the 3D imaging of AM materials by means of X-ray Computed Tomography at the lab and at synchrotron, and the residual stress characterization by diffraction (nondestructive technique). Also, two successful research project in collaboration with CAM2, Sweden are presented. T2 - CAM2 Annual Meeting CY - Gothenburg, Sweden DA - 25.10.2023 KW - Additive manufacturing KW - Residual stress KW - X-ray computed tomography PY - 2023 AN - OPUS4-58828 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro A1 - Roveda, Ilaria A1 - Serrano-Munoz, Itziar A1 - Haubrich, J. A1 - Requena, G. T1 - Prediction of the fatigue limit of additively manufactured metallic materials N2 - Structural alloys are largely employed in key industrial sectors and their demand is predicted to rise rapidly for the next decades. Most of these materials require a large amount of energy for extraction and manufacturing, which causes the emission of greenhouse gases and other pollutants. Therefore, strategies for improving the sustainability of structural metallic alloys are urgently needed. Additive Manufacturing (AM), in particular Laser Powder Bed Fusion (PBF-LB/M), aims to be a sustainable manufacturing process, as it allows the build-up of complex geometry in near net-shape from 3D models, while minimizing material waste and the energy required for the process and post-process treatments. Nevertheless, the application of additively manufactured parts in structural safety-relevant applications is still hindered by the poor fatigue performance. The cause of this has been mainly attributed to the presence of manufacturing defects and surface roughness. Therefore, a huge effort has been made to optimize the process parameters and to introduce post-process treatments to minimize the defect content. However, material flaws cannot be fully eliminated, but these can be considered in a damage tolerance framework for the prediction of the fatigue performance of additively manufactured metallic materials, which is essential for part design and qualification. This work aims at presenting different modelling strategies for the prediction of the fatigue limit of AM metals. Simple empirical models and more complex models based on fatigue short crack propagation are proposed. The investigated material is an AlSi10Mg alloy fabricated by PBF-LB/M and subjected to two different low-temperature heat-treatments (265°C for 1 h and 300°C for 2h). The results show that the models can provide good approximation of the fatigue limits and help in the interpretation of the scatter of fatigue data. T2 - ASTM International Conference on Advanced Manufacturing CY - Washington DC, USA DA - 30.10.2023 KW - Additive Manufacturing KW - AlSi10Mg KW - Fatigue KW - Residual stress KW - Microstructure PY - 2023 AN - OPUS4-58866 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Roveda, Ilaria A1 - Serrano Munoz, Itziar A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - Effect of heat treatment on residual stress in additively manufactured AlSi10Mg N2 - Al-Si alloys produced by Laser Powder Bed Fusion (PBFLB) allow the fabrication of lightweight free-shape components. Due to the extremely heterogeneous cooling and heating, PBF-LB induces high magnitude residual stress (RS) and a fine Si microstructure. As the RS can be deleterious to the fatigue resistance of engineering components, great efforts are focused on understanding their evolution in as-built state (AB) and after post-process heat treatments (HT). RS in single edge notch bending (SENB) subjected to different HT are investigated (HT1: 1h at 265°C and HT2: 2h at 300°C). T2 - ESRF User Meeting 2023 CY - Grenoble, France DA - 07.02.2023 KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress PY - 2023 AN - OPUS4-56982 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana T1 - 3D imaging and residual stress analysis for AM Materials N2 - The overview of the activity of Federal Institute for Material Research and Testing (BAM, Belin, Germany) in the field of additively manufacturing material characterization will be presented. The research of our group is focused on the 3D imaging of AM materials by means of X-ray Computed Tomography at the lab and at synchrotron, and the residual stress characterization by diffraction (nondestructive technique). T2 - Seminar at Integrated Additive Manufacturing center, Politecnico Torino CY - Turin, Italy DA - 14.02.2023 KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress KW - Computed tomography KW - Synchrotron X-ray diffraction PY - 2023 AN - OPUS4-57047 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Serrano Munoz, Itziar A1 - Roveda, Ilaria A1 - Requena, Guillermo A1 - Evans, Alexander A1 - Madia, Mauro A1 - Haubrich, Jan T1 - Influence of microstructure and residual stress state on the fatigue behaviour of a PBF-LB/M AlSi10Mg alloy N2 - The high cooling rates (~106 K/s) occurring during Laser Powder Bed Fusion (PBF-LB/M) of AlSi10Mg induce to the formation of a fine nanometric silicon network in the as-built condition. Such unprecedented microstructure enhances the mechanical strength when compared to equivalent as-cast materials. Nevertheless, PBF-LB/M also leads to high magnitude residual stress (RS) due to the extreme localized temperature gradients. The presence of RS can be detrimental to the fatigue life of engineering components, and great efforts are focused on understanding their generation and evolution after post-process heat treatments. Typically, T6 heat treatments are used to mitigate RS and improve mechanical performances by Mg2Si precipitation during ageing at 160-180°C. Nevertheless, the solutionizing at 500-540°C vanishes the fine silicon network, leading to the formation of micrometric (average of ~2-5 µm) polygonal Si particles, similar to those observed in T6 heat-treated Al-Si cast materials. Therefore, the aim of this work is to evaluate the ability of two so-called low temperature heat treatments (i.e., at 265°C and 300°C) to mitigate RS while retaining the fine as-built microstructure inherent to PBF-LB/M AlSi10Mg. The fatigue behavior of the as-built material is subsequently compared to the two low temperature conditions. T2 - LightMat 2023 CY - Trondheim, Norway DA - 21.06.2023 KW - AlSi10Mg KW - Fatigue crack propagation KW - Residual stress KW - Post processing heat treatment PY - 2023 AN - OPUS4-57807 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Serrano Munoz, Itziar T1 - 3D imaging and residual stress analysis for AM Materials N2 - Metal Additive Manufacturing (AM) technologies such as Laser Powder Bed Fusion (LPBF) are characterized by layer wise construction, which enable advancements of component design, leading to potential efficiency and performance improvements. However, the rapid cooling rates associated with the process consequently leads to the generation of high magnitude residual stresses (RS). Therefore, a deep understanding of the formation of RS, the influence of process parameters on their magnitude and the impact on mechanical performance is crucial for widespread application. The experimental characterization of these RS is essential for safety related engineering application and supporting the development of reliable numerical models. Diffraction-based methods for RS analysis using high energy synchrotron X-rays and neutrons enable non-destructive spatially resolved characterization of both surface and bulk residual stresses in complex components. This presentation will provide an overview of recent research conducted by the BAM at large scale facilities for the characterization of residual stresses in LPBF metallic alloys. Special focus will be given to the challenges posed by textured LPBF materials for the reliable choice of the diffraction elastic constants (DECs), which is crucial to the accurate calculation of the level of RS. T2 - Seminar at LTDS, Ecole Centrale de Lyon CY - Lyon, France DA - 15.06.2023 KW - Residual stress KW - Additive manufacturing KW - Diffraction methods PY - 2023 AN - OPUS4-57808 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Hensel, J. T1 - Consideration of manufacturing-related stresses and cold crack avoidance in high-strength steels WAAM components N2 - High-strength steels offer great potential in weight-optimised modern steel structures. Additive manufacturing processes, such as Wire Arc Additive Manufacturing (WAAM), enable near-net-shape manufacturing of complex structures and more efficient manufacturing, offering significant savings in costs, time, and resources. Suitable filler materials for WAAM are already commercially available. However, the lack of knowledge or technical guidelines regarding welding residual stresses during manufacturing and operation in connection with cold cracking risk limit their industrial application significantly. In a project of BAM and TU Chemnitz, the influences and complex interactions of material, manufacturing process, design and processing steps on residual stress evolution are investigated. By developing process recommendations and a special cold cracking test, economic manufacturing, and stress-appropriate design of high-strength steel WAAM components are main objectives. The present study focuses on determining the influence of heat control (interpass temperature, heat input, cooling time) and the design aspects of the components on the hardness and residual stresses, which are analysed by X-ray diffraction. Defined reference specimens, i.e., hollow cuboids, are automatically welded with a special WAAM solid wire. The influences of wall length, wall thickness and wall height on the residual stresses are analysed. Geometric properties can be selectively adjusted by wire feed and welding speed but cannot be varied arbitrarily. This was addressed by adapted build-up strategies. The results indicate a significant influence of the heat control and the wall height on the residual stresses. The interpass temperature, wall thickness and wall length are not significant. These analyses allow recommendations for standards and manufacturing guidelines, enabling a safe and economic manufacturing of high-strength steel components. T2 - European Steel Technology and Application Days CY - Düsseldorf, Germany DA - 14.06.2023 KW - DED-arc KW - Additive manufacturing KW - Heat control KW - High-strength filler metals KW - Residual stress PY - 2023 AN - OPUS4-57691 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Hensel, J. T1 - Influence of the WAAM process and design aspects on residual stresses in high-strength structural steels N2 - Wire arc additive manufacturing (WAAM) enables the efficient production of weight-optimized modern engineering structures. Further increases in efficiency can be achieved by using high-strength structural steels. Commercial welding consumables for WAAM are already available on the market. Lack of knowledge and guidelines regarding welding residual stress and component safety during production and operation leads to severely limited use for industry applications. The sensitive microstructure of high-strength steels carries a high risk of cold cracking; therefore, residual stresses play a crucial role. For this reason, the influences of the material, the WAAM process, and the design on the formation of residual stresses and the risk of cold cracking are being investigated. The material used has a yield strength of over 800 MPa. This strength is adjusted via solid solution strengthening and a martensitic phase transformation. The volume expansion associated with martensite formation has a significant influence on the residual stresses. The focus of the present investigation is on the additive welding parameters and component design on their influence on hardness and residual stresses, which are analyzed by means of X-ray diffraction (XRD). Reference specimens (hollow cuboids) are welded fully automated with a systematic variation of heat control and design. Welding parameters and AM geometry are correlated with the resulting microstructure, hardness, and residual stress state. Increased heat input leads to lower tensile residual stresses which causes unfavorable microstructure and mechanical properties. The component design affects heat dissipation conditions and the intensity of restraint during welding and has a significant influence on the residual stress. KW - DED-arc KW - Additive manufacturing KW - High-strength steel filler metal KW - Residual stress PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-572698 SN - 1878-6669 VL - 67 IS - 4 SP - 987 EP - 996 PB - Springer CY - Berlin AN - OPUS4-57269 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Evans, Alexander A1 - Kromm, Arne A1 - Sommer, Konstantin A1 - Werner, Tiago A1 - Kelleher, J. A1 - Bruno, Giovanni A1 - Kannengießer, Thomas T1 - Towards the optimization of post-laser powder bed fusion stress-relieve treatments of stainless steel 316L N2 - This study reports on the stress relaxation potential of stress-relieving heat treatments for laser powder bed fused 316L. The residual stress is monitored non-destructively using neutron diffraction before and after the heat treatment. Moreover, the evolution of the microstructure is analysed using scanning electron microscopy. The results show, that a strong relaxation of the residual stress is obtained when applying a heat treatment temperature at 900°C. However, the loss of the cellular substructure needs to be considered when applying this heat treatment strategy. KW - Residual stress KW - Additive manufacturing KW - Neutron diffraction KW - Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-536045 SN - 1543-1940 VL - 52 IS - 12 SP - 5342 EP - 5356 PB - Springer CY - Boston AN - OPUS4-53604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Mishurova, Tatiana A1 - Serrano-Munoz, Itziar A1 - Fritsch, Tobias A1 - Schröder, Jakob A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Residual stresses Analysis in Additively Manufactured alloys using neutron diffraction (L-PBF) N2 - An overview of recent progress at BAM of residual stress analysis in additively manufactured, in particular Laser Powder Bed Fusion of metallics materials, using neutron diffraction will be presented. This will cover important topics of the stress-free reference, the diffraction elastic moduli and principal stress determination. T2 - AWT-Fachausschuss 13 "Eigenspannungen" CY - Berlin, Germany DA - 28.03.2023 KW - AGIL KW - Residual stress KW - Additive manufacturing KW - Laser Powder Bed Fusion KW - Diffraction PY - 2023 AN - OPUS4-59177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zurcher, Theo A1 - Serrano-Munoz, Itziar A1 - Mishurova, Tatiana A1 - Abreu Faria, Guilherme A1 - Degener, Sebastian A1 - Fridrici, Vincent A1 - Charkaluk, Eric A1 - Bruno, Giovanni T1 - Sliding wear resistance and residual stresses of parts repaired by laser metal deposition N2 - Large temperature gradients inherent to additive manufacturing (AM) processes induce large residual stress (RS) in the final part. Because RS can influence the tribological properties, this study focuses on the relationship between wear sliding properties and RS in IN718 coatings. Such coatings were deposited with a Laser metal deposition (LMD) machine using two different scanning strategies. The wear resistance and RS state were investigated after surface milling. RS were measured before and after wear tests on a reciprocating sliding test apparatus. Two different X-ray diffraction techniques were employed to measure the surface and subsurface state RS: Laboratory Energy Dispersive X-ray Diffraction (LEDXD) and Synchrotron X-ray Energy Dispersive Diffraction (SXEDD). Due to the milling process, the coatings show similar depth distributions of RS from 22 to 92 μm depth, but exhibit different magnitudes depending on the scanning strategy used. Reciprocating sliding wear tests induced high compressive residual stresses that erased the initial RS state, and a similar wear behavior was observed in the two samples. These samples possess similar texture and grain morphology. This demonstrates that the influence of RS on wear resistance is a second-order effect. Nevertheless, it was observed that RS can still impact the wear performance at the early testing stages of the repaired parts. KW - Additive manufacturing KW - Wear resistance KW - Residual stress PY - 2023 U6 - https://doi.org/10.1007/s10853-023-09129-4 SN - 0022-2461 SP - 1 EP - 18 PB - Springer AN - OPUS4-59084 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wandtke, Karsten ED - Becker, Amadeus ED - Schröpfer, Dirk ED - Kromm, Arne ED - Kannengießer, Thomas ED - Scharf-Wildenhain, R. ED - Hälsig, A. ED - Hensel, J. T1 - Residual Stress Evolution during Slot Milling for Repair Welding and Wire Arc Additive Manufacturing of High-Strength Steel Components N2 - High-strength steels offer potential for weight optimization due to reduced wall thicknesses in modern constructions. Additive manufacturing processes such as Wire Arc Additive Manufacturing (WAAM) enable the resource-efficient production of structures. In the case of defects occurring in weld seams orWAAM components due to unstable process conditions, the economical solution is local gouging or machining and repair welding. It is important to understand the effects of machining steps on the multiaxial stress state in conjunction with the design-related shrinkage restraints. Research into how welding and slot milling of welds andWAAM structures affects residual stresses is still lacking. For this reason, component-related investigations with high-strength steels with yield strengths ≥790 MPa are carried out in our research. In-situ digital image correlation (DIC) and ex-situ X-ray diffraction (XRD) were used to analyze the stresses and strains induced on specimens during and after milling. The systematic analyses revealed a significant interaction of the stiffness and microstructure of the specimens with the initial residual stresses induced by welding. Subsequent repair welds can result in significantly higher residual stresses. KW - High strength steels KW - Additive manufacturing KW - Residual stress KW - Repair welding KW - Ditigtal image correlation PY - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-593515 VL - 14 IS - 1 SP - 1 EP - 11 PB - MDPI CY - Basel AN - OPUS4-59351 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Wandtke, Karsten A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Hensel, J. T1 - Residual stress formation in DED-arc manufactured high strength steel components N2 - Additive manufacturing (AM) processes enable the efficient production of advanced constructions. New developments in topology optimization are leading to weight-optimized designs of increasing complexity. Direct energy deposition processes (DED) such as wire and arc-based additive manufacturing are an important method of additive manufacturing. The wire filler metals enable a wide range of materials, while the arc process provides a high deposition rate compared to laser and powder-based processes. Combined with the use of high-strength steels, the thickness of walls or components can be significantly reduced in the context of lightweight construction, which results in significant savings in energy, costs, time and resources. Suitable high-strength steel filler metals are commercially available for DED-arc AM processes. However, guidelines and quantitative knowledge about welding stresses and cold cracking issues during component production and service are lacking. This limits the industrial application considerably. In a joint project of BAM and Chemnitz University of Technology, the main influences and complex interactions of material, production process, design and processing steps on the residual stress level are investigated. The aim is to develop processing recommendations and a cold cracking test for economical processing and stress-related design of high-strength steels with DED-arc. This study focuses on residual stress analysis by neutron diffraction (ND) and X-ray diffraction (XRD) on defined test specimens. The ND analysis were performed at the Paul Scherrer Institute- Villigen, Switzerland (PSI) and the XRD analysis at BAM. The study shows a quantitative and qualitative comparison of the residual stress magnitudes and distribution between the component bulk (ND) and surface (XRD) analyses. The ND analysis reveals that in DED-arc AM walls the residual stresses dominate in the direction of welding and are negligibly small in each case transverse to the direction of welding. The topology of the analyzed residual stresses shows almost identical residual stress maps compared to XRD. In addition, the residual stresses are significantly influenced by the solid phase transformation of the material due to low cooling times and less post heat treatment cycles of following AM layers in the area of the top layer. T2 - IIW Intermediate Meeting C-II/CIX CY - Munich, Germany DA - 06.03.2023 KW - Additive manufacturing KW - High strength steel KW - Residual stress PY - 2023 AN - OPUS4-59307 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritsch, Tobias A1 - Sprengel, Maximilian A1 - Evans, Alexander A1 - Farahbod-Sternahl, L. A1 - Saliwan Neumann, Romeo A1 - Hofmann, M. A1 - Bruno, Giovanni T1 - On the determination of residual stresses in additively manufactured lattice structures N2 - The determination of residual stresses becomes more complicated with increasing complexity of the structures investigated. Additive manufacturing techniques generally allow the production of ‘lattice structures’ without any additional manufacturing step. These lattice structures consist of thin struts and are thus susceptible to internal stress-induced distortion and even cracks. In most cases, internal stresses remain locked in the structures as residual stress. The determination of the residual stress in lattice structures through nondestructive neutron diffraction is described in this work. It is shown how two difficulties can be overcome: (a) the correct alignment of the lattice structures within the neutron beam and (b) the correct determination of the residual stress field in a representative part of the structure. The magnitude and the direction of residual stress are discussed. The residual stress in the strut was found to be uniaxial and to follow the orientation of the strut, while the residual stress in the knots was more hydrostatic. Additionally, it is shown that strain measurements in at least seven independent directions are necessary for the estimation of the principal stress directions. The measurement directions should be chosen according to the sample geometry and an informed choice on the possible strain field. If the most prominent direction is not measured, the error in the calculated stress magnitude increases considerably. KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress KW - Principal stress components KW - Neutron diffraction KW - Lattice structures PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-520663 SN - 1600-5767 VL - 54 SP - 228 EP - 236 AN - OPUS4-52066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Hensel, J. T1 - Einfluss trennender Fertigungsschritte auf die Eigenspannungen in additiv gefertigten Bauteilen aus hochfestem Stahl N2 - Additive Fertigungsverfahren wie das Wire Arc Additive Manufacturing (WAAM) ermöglichen die effiziente Fertigung von gewichtsoptimierten endkonturnahen Strukturen in modernen Stahlkonstruktionen. Ihre Effizienz kann weiter durch die Verwendung von hochfesten Stählen gesteigert werden. Dies erlaubt eine signifikante Einsparung von Kosten, Zeit und Ressourcen. Entsprechende Schweißzusatzwerkstoffe für Lichtbogenschweißverfahren sind kommerziell verfügbar. Fehlende Richtlinien und fehlende quantitative Kenntnisse über die schweißtechnische Beanspruchung während der Fertigung und im Betrieb limitieren den industriellen Einsatz stark. Daher werden in einem aktuellen Vorhaben (IGF-Nr. 21162 BG) der BAM und TU Chemnitz die wesentlichen Einflüsse und komplexen Interaktionen durch Werkstoff, Fertigungsprozess, Konstruktion und trennende Fertigungsschritte auf den Beanspruchungszustand untersucht. Der vorliegende Beitrag fokussiert hierfür die Auswirkungen trennender Fertigungsschritte auf Verzug und Eigenspannungen definierter WAAM-Prüfkörper. Die Eigenspannungsanalyse erfolgt mittels Röntgenbeugung. Die große Anzahl an Ergebnissen von zuvor untersuchten Referenzproben, die mit einem speziellen WAAM-Massivdraht (Streckgrenze >820 MPa) bei unterschiedlicher Wärmeführung und Geometrie vollautomatisiert geschweißt wurden, lässt eine Korrelation der Messdaten zu. Hierzu erfolgt die Analyse des Ausgangszustandes und abschließend des Zustandes nach trennender Bearbeitung, welche begleitend mittels digitaler Bildkorrelation hinsichtlich des Verzuges untersucht wurden. So ist zu beobachten, dass die Geometrie deutlichen Einfluss auf Relaxation und Umlagerung der Eigenspannungen hat und damit die Risssicherheit positiv beeinflussen kann. T2 - 23. Werkstofftechnisches Kolloquium CY - Chemnitz, Germany DA - 29.03.2023 KW - Additive Fertigung KW - Hochfester Stahl KW - Eigenspannungen KW - Residual stress PY - 2023 AN - OPUS4-59231 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana T1 - 3D Imaging and residual stress analysis of additively manufactured materials N2 - The focus of the presentation focus will be on 3D imaging by means of X-ray Computed Tomography (XCT) at the lab and at synchrotron, and the non-destructive residual stress (RS) characterization by diffraction of additively manufactured (AM) materials in BAM (Berlin, Germany). The manufacturing defects and high RS are inherent of AM techniques and affect structural integrity of the components. Using XCT the defects size and shape distribution as well as geometrical deviations can be characterized, allowing the further optimization of the manufacturing process. Diffraction-based RS analysis methods using neutron and synchrotron X-rays at large scale facilities offer the possibility to non-destructively spatially resolve both surface and bulk RS in complex components and track their changes following applied thermal or mechanical loads. T2 - The International Symposium on Nondestructive Characterization of Materials 2023 CY - Zurich, Switzerland DA - 15.08.2023 KW - Additive manufacturing KW - Residual stress KW - X-ray computed tomography PY - 2023 AN - OPUS4-58113 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Pelkner, Matthias A1 - Lyamkin, Viktor A1 - Pittner, Andreas A1 - Werner, Daniel A1 - Wimpory, R. A1 - Boin, M. A1 - Kreutzbruck, Marc A1 - Bruno, Giovanni T1 - Influence of the microstructure on magnetic stray fields of low-carbon steel welds N2 - This study examines the relationship between the magnetic mesostructure with the microstructure of low carbon steel tungsten inert gas welds. Optical microscopy revealed variation in the microstructure of the parent material, in the heat affected and fusion zones, correlating with distinctive changes in the local magnetic stray fields measured with high spatial resolution giant magneto resistance sensors. In the vicinity of the heat affected zone high residual stresses were found using neutron diffraction. Notably, the gradients of von Mises stress and triaxial magnetic stray field modulus follow the same tendency transverse to the weld. In contrast, micro-X-ray fluorescence characterization indicated that local changes in element composition had no independent effect on magnetic stray fields. KW - TIG-welding KW - GMR sensors KW - Magnetic stray field KW - Neutron diffraction KW - Residual stress KW - Microstructure KW - Low carbon steel PY - 2018 U6 - https://doi.org/10.1007/s10921-018-0522-0 SN - 0195-9298 SN - 1573-4862 VL - 37 IS - 3 SP - 66,1 EP - 18 PB - Springer US CY - New York AN - OPUS4-45855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Charmi, Amir A1 - Falkenberg, Rainer A1 - Ávila, Luis A1 - Mohr, Gunther A1 - Sommer, Konstantin A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Saliwan Neumann, Romeo A1 - Evans, Alexander A1 - Skrotzki, Birgit T1 - Mechanical anisotropy of additively manufactured stainless steel 316L: An experimental and numerical study N2 - The underlying cause of mechanical anisotropy in additively manufactured (AM) parts is not yet fully understood and has been attributed to several different factors like microstructural defects, residual stresses, melt pool boundaries, crystallographic and morphological textures. To better understand the main contributing factor to the mechanical anisotropy of AM stainless steel 316L, bulk specimens were fabricated via laser powder bed fusion (LPBF). Tensile specimens were machined from these AM bulk materials for three different inclinations: 0◦, 45◦, and 90◦ relative to the build plate. Dynamic Young’s modulus measurements and tensile tests were used to determine the mechanical anisotropy. Some tensile specimens were also subjected to residual stress measurement via neutron diffraction, porosity determination with X-ray micro-computed tomography (μCT), and texture analysis with electron backscatter diffraction (EBSD). These investigations revealed that the specimens exhibited near full density and the detected defects were spherical. Furthermore, the residual stresses in the loading direction were between −74 ± 24 MPa and 137 ± 20 MPa, and the EBSD measurements showed a preferential ⟨110⟩ orientation parallel to the build direction. A crystal plasticity model was used to analyze the elastic anisotropy and the anisotropic yield behavior of the AM specimens, and it was able to capture and predict the experimental behavior accurately. Overall, it was shown that the mechanical anisotropy of the tested specimens was mainly influenced by the crystallographic texture. KW - Mechanical anisotropy KW - Residual stress KW - Crystal plasticity KW - Selective laser melting (SLM) KW - Laser beam melting (LBM) PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-511719 SN - 0921-5093 VL - 799 SP - 140154 PB - Elsevier B.V. AN - OPUS4-51171 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Jakob A1 - Evans, Alexander A1 - Luzin, V. A1 - Abreu Faria, G. A1 - Degener, Sebastian A1 - Polatidis, E. A1 - Čapek, J. A1 - Kromm, Arne A1 - Dovzhenko, G. A1 - Bruno, Giovanni T1 - Texture-based residual stress analysis of laser powder bed fused Inconel 718 parts N2 - Although layer-based additive manufacturing methods such as laser powder bed fusion (PBF-LB) offer an immense geometrical freedom in design, they are typically subject to a build-up of internal stress (i.e. thermal stress) during manufacturing. As a consequence, significant residual stress (RS) is retained in the final part as a footprint of these internal stresses. Furthermore, localized melting and solidification inherently induce columnar-type grain growth accompanied by crystallographic texture. Although diffraction-based methods are commonly used to determine the RS distribution in PBF-LB parts, such features pose metrological challenges in their application. In theory, preferred grain orientation invalidates the hypothesis of isotropic material behavior underlying the common methods to determine RS. In this work, more refined methods are employed to determine RS in PBF-LB/M/IN718 prisms, based on crystallographic texture data. In fact, the employment of direction-dependent elastic constants (i.e. stress factors) for the calculation of RS results in insignificant differences from conventional approaches based on the hypothesis of isotropic mechanical properties. It can be concluded that this result is directly linked to the fact that the {311} lattice planes typically used for RS analysis in nickel-based alloys have high multiplicity and less strong texture intensities compared with other lattice planes. It is also found that the length of the laser scan vectors determines the surface RS distribution in prisms prior to their removal from the baseplate. On removal from the baseplate the surface RS considerably relaxes and/or redistributes; a combination of the geometry and the scanning strategy dictates the sub-surface RS distribution. KW - Additive manufacturing KW - Electron backscattered diffraction KW - Principal stress KW - Residual stress PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-578331 SN - 1600-5767 VL - 56 IS - Pt 4 SP - 1076 EP - 1090 AN - OPUS4-57833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - John, Sebastian A1 - Eisermann, René A1 - Mair, Georg T1 - Application of an experimental modal analysis on composite pressure vessels for monitoring prestress conditions N2 - Due to high specific stiffness, fibre reinforced plastics are the dominant material group for the design of mobile pressure vessels. At the Federal Institute of Materials Research and Testing (BAM) aging process of composite pressure vessels is studied to be able to give more accurate lifetime predictions in future. Investigations are based on type III breathing air cylinders consisting of an aluminium tank which is fully wrapped with carbon fibre reinforced plastics. Goal is to detect changes of residual stresses over life time which directly affect fatigue strength. Within this paper an approach is presented to monitor residual stresses via an experimental modal analysis (EMA). First, the influence of changed stress conditions on modal parameters is analysed via a numerical study. Secondly, a test bench for an EMA is set up. To be able to analyse cylinders of different prestress condition, several specimens are prestress modified via high-temperature and high-pressure treatment. During modification processes, specimens are monitored via optical fibres to control prestress modifications. Through experimental measurements of the modified specimens via EMA changes in prestressing can be detected. Finally, validity and accuracy of the EMA is evaluated critically by comparing all numerically and experimentally obtained data. T2 - INTERNOISE 2018 CY - Chicago, Illinois, USA DA - 25.08.2018 KW - Modal analysis KW - Residual stress KW - Composite KW - Pressure vessel PY - 2018 SN - 978-0-7918-5142-5 SP - 6143, 1 EP - 10 AN - OPUS4-46329 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - John, Sebastian T1 - Beitrag zur Analyse des Eigenspannungsverhaltens von Composite-Hochdruckspeichern mit metallischem Liner N2 - Bei der Auslegung von Druckbehältern kommen, auf Grund ihrer hohen spezifischen Festigkeit, vermehrt Faserverbundwerkstoffe zum Einsatz. Durch eine hohe Streuung von Material- und Produktionsparametern sowie unterschiedlichster Belastungsszenarien gestaltet sich jedoch Aussagen über die Lebensdauer sowie eine Festlegung sinnvoller Prüffristen als schwierig. Im Fokus der Untersuchungen steht ein Behälterdesign mit metallischem Liner und einem kohlenstofffaserverstärkten Kunststoffverbund, wobei die Lebensdauer maßgeblich durch den im Metall vorherrschenden Eigenspannungszustand bestimmt wird. Mit Hilfe einer alterungsbegleitenden Eigenspannungsanalyse werden Eigenspannungsveränderungen erfasst und in einem erarbeiteten Betriebsfestigkeitsmodell berücksichtigt. Durch eine Nachstellung verschiedener Belastungsszenarien kann gezeigt werden, dass durch die Berücksichtigung einer veränderlichen Eigenspannung die Anzahl ertragbarer Lastwechsel bis zum Versagen sowie damit verbundene Überlebenswahrscheinlichkeiten mit einer erhöhten Genauigkeit abgeschätzt werden können. KW - Komposit KW - Druckbehälter KW - Pressure vessel KW - Eigenspannung KW - Residual stress KW - Alterung KW - Aging KW - Faserverbund KW - Fibre reinforced plastics KW - Composite PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-520269 SN - 2512-5141 SN - 2512-515X SN - 978-3-7983-3179-2 SN - 978-3-7983-3180-8 VL - 10 SP - 1 EP - 188 PB - Universitätsverlag der TU Berlin CY - Berlin AN - OPUS4-52026 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Saliwan Neumann, Romeo A1 - Farahbod, Lena A1 - Haberland, Christoph A1 - Portella, Pedro Dolabella T1 - Influence of support configurations on the characteristics of selective laser-melted Inconel 718 N2 - Samples fabricated using two different support configurations by following identical scan strategies during selective laser melting of superalloy Inconel 718 were characterized in this study. Characterization methods included optical microscopy, electron back-scattered diffraction and x-ray diffraction residual stress measurement. For the scan strategy considered, microstructure and residual stress development in the samples were influenced by the support structures. However, crystallographic texture intensity and the texture components formed within the core part of the samples were almost independent of the support. The formation of finer grains closer to the support as well as within the columnar grain boundaries resulted in randomization and texture intensity reduction by nearly half for the sample built on a lattice support. Heat transfer rates dictated by the support configurations in addition to the scan strategy influenced the microstructure and residual stress development in selective laser-melted Inconel 718 samples. KW - Additive manufacturing KW - Selective laser melting KW - Support configurations KW - Microstructure and texture KW - Residual stress PY - 2018 U6 - https://doi.org/10.1007/s11837-017-2703-1 SN - 1047-4838 SN - 1543-1851 VL - 70 IS - 3 SP - 343 EP - 348 PB - Springer CY - USA AN - OPUS4-44175 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - John, Sebastian A1 - Mair, Georg A1 - Schoppa, André A1 - Szczepaniak, Mariusz T1 - Monitoring of residual stresses in composite pressure vessels via modal analysis N2 - Within a current research project at the Federal Institute for Materials Testing and Research (BAM), the degradation process of composite pressure vessels is studied to be able to give more accurate lifetime predictions in future. The presented research is based on type III pressure vessels consisting of an aluminium tank which is fully wrapped with carbon fibre reinforced plastics. Focus is set on the analysis of residual stresses which are induced into the pressure vessel during manufacturing process in order to increase high cycle fatigue. However, with increasing lifetime residual stress conditions do change. To be able to measure and monitor stress conditions, the application of a non-destructive measurement method is aspired. In this paper, potential of an experimental modal analysis is worked out to capture and monitor aging and degradation effects in pressure vessels. With the presented method, information about changes in residual stress can be obtained via an analysis of the modal parameters. To realize an application, first, a finite element simulation is used to prove and evaluate potential capability and validity. In the following, a test bench is set up and successively optimized in its accuracy and efficiency. Sensitivity of the applied measurement technique is experimentally ascertained trough the measurement of several prestress modified pressure vessels. Finally, experimental results are interpreted and evaluated with the help of numerically gained findings. T2 - NOVEM 2018 CY - St. Eulalia, Ibiza, Spain DA - 07.05.2018 KW - Composite pressure vessel KW - Residual stress KW - Modal analysis PY - 2018 VL - 6 SP - Paper 175090, 1 EP - 9 AN - OPUS4-45220 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - John, Sebastian A1 - Mair, Georg A1 - Schoppa, André A1 - Szcepaniak, Marisz T1 - Monitoring of residual stresses in composite pressure vessels via modal analysis N2 - At the Bundesanstalt für Materialforschung und –prüfung (BAM), within a recent research project, the aging process of composite pressure vessels is investigated in order to be able to give more accurate lifetime predictions in future. All investigations are primarily based on type III pressure vessels consisting of an aluminium tank which is fully wrapped with carbon fibre reinforced plastics. Research is focused on residual stresses which are induced into the pressure vessel during manufacturing process in order to increase high cycle fatigue. However, with increasing lifetime residual stress conditions of type III pressure vessels change. For measuring and monitoring inner stress conditions, the application of a non-destructive measurement method is aspired. Within this paper, the potential of an experimental modal analysis is tested to determine aging and degradation effects of pressure vessels. Based on this method, information about changes of the residual stresses can be obtained via an analysis of the modal parameters. Realizing this, first a finite element model is used to prove and evaluate potential capability and validity for the application of an experimental modal analysis. Based on this, a test bench is set up and successively optimized in its accuracy and efficiency. The sensitivity of the applied measurement technique is experimentally evaluated via measuring multiple prestress modified pressure vessels. Furthermore, a selection of prestress modified pressure vessels is monitored via the presented method. Finally, experimentally obtained results are interpreted and evaluated with the help of numerically gained finding. T2 - NOVEM 2018 CY - St. Eulalia, Spain DA - 08.05.2018 KW - Composite pressure vessel KW - Residual stress KW - Cod-age KW - Modal analysis PY - 2018 AN - OPUS4-45242 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Kromm, Arne A1 - Seyfert, Christoph A1 - Farahbod, Lena A1 - Haberland, Christoph A1 - Schneider, Judith Ann A1 - Portella, Pedro Dolabella A1 - Bruno, Giovanni T1 - Effect of hatch length on the development of microstructure, texture and residual stresses in selective laser melted superalloy Inconel 718 N2 - In the present study, samples fabricated by varying the deposition hatch length during selective laser melting of nickel based superalloy Inconel 718 were investigated. Microstructure and texture of these samples was characterized using scanning electron microscopy, combined with electron back-scattered diffraction, and residual stress assessment, using neutron diffraction method. Textured columnar grains oriented along the sample building direction were observed in the shorter hatch length processed sample. A ten-fold increase in the hatch length reduced the texture intensity by a factor of two attributed to the formation of finer grains in the longer hatch length sample. Larger gradients of transverse residual stress in the longer hatch length sample were also observed. Along the build direction, compressive stresses in the shorter hatch length and negligible stresses for the longer hatch length specimen were observed. Changes to the temperature gradient (G) in response to the hatch length variation, influenced the G to growth rate (R) ratio and the product G × R, in agreement with the microstructures and textures formed. For the residual stress development, geometry of the part also played an important role. In summary, tailored isotropy could be induced in Inconel 718 by a careful selection of parameters during selective laser melting. KW - Additive manufacturing KW - Nickel-based superalloy KW - Microstructure and texture KW - Residual stress KW - Electron back-scattered diffraction KW - Neutron diffraction PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0264127517308018 U6 - https://doi.org/10.1016/j.matdes.2017.08.049 SN - 0264-1275 VL - 134 SP - 139 EP - 150 PB - Elsevier CY - Oxford, UK AN - OPUS4-41606 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - John, Sebastian A1 - Eisermann, René A1 - Mair, Georg T1 - Application of an experimental modal analysis on composite pressure vessels for monitoring prestress conditions N2 - Due to high specific stiffness, fibre reinforced plastics are the dominant material group for the design of mobile pressure vessels. At the Federal Institute of Materials Research and Testing (BAM) aging process of composite pressure vessels is studied to be able to give more accurate lifetime predictions in future. Investigations are based on type III breathing air cylinders consisting of an aluminium tank which is fully wrapped with carbon fibre reinforced plastics. Goal is to detect changes of residual stresses over life time which directly affect fatigue strength. Within this paper an approach is presented to monitor residual stresses via an experimental modal analysis (EMA). First, the influence of changed stress conditions on modal parameters is analysed via a numerical study. Secondly, a test bench for an EMA is set up. To be able to analyse cylinders of different prestress condition, several specimens are prestress modified via high-temperature and high-pressure treatment. During modification processes, specimens are monitored via optical fibres to control prestress modifications. Through experimental measurements of the modified specimens via EMA changes in prestressing can be detected. Finally, validity and accuracy of the EMA is evaluated critically by comparing all numerically and experimentally obtained data. T2 - INTERNOISE 2018 CY - Chicago, USA DA - 25.08.2018 KW - Residual stress KW - Composite KW - Pressure vessel KW - Modal analysis PY - 2018 AN - OPUS4-46330 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander A1 - Mohr, Gunther A1 - Hilgenberg, Kai A1 - Straße, Anne A1 - Gumenyuk, Andrey A1 - Winterkorn, René A1 - Pittner, Andreas A1 - Sommer, Konstantin A1 - Bettge, Dirk A1 - Kranzmann, Axel A1 - Nolze, Gert A1 - Avila, Luis A1 - Rehmer, Birgit A1 - Charmi, Amir A1 - Falkenberg, Rainer A1 - Skrotzki, Birgit A1 - Werner, Tiago A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Kromm, Arne A1 - Thiede, Tobias A1 - Bruno, Giovanni T1 - Ageing in additively manufactured metallic components: from powder to mechanical failure” an overview of the project agil N2 - An overview of the BAM funed Focus Area Materials Project "AGIL" will be presented. AGIL focussed on the stdiy of the ageing characteristics of additively manufactured austenitic stainless steel with a "powder to mechanical failure" Approach. Recent Highlights are presented and a perspective for future studies. T2 - Workshop on Additive Manufacturing CY - BAM, Berlin, Germany DA - 13.05.2019 KW - Residual stress KW - Additive Manufacturing KW - Non-destructive testing KW - Microstructure characterisation KW - Tensile testing KW - Fatigue KW - Crystal Plasticity Modelling KW - Crack propagation PY - 2019 AN - OPUS4-49823 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, Katia A1 - Haubrich, Jan A1 - Requena, Guillermo A1 - Bruno, Giovanni A1 - Rehmer, Birgit T1 - Influence of residual stress and microstructure on mechanical performance of LPBF TI-6AL-4V N2 - Ti-6Al-4V alloy is intensively used in the aerospace industry because of its high specific strength. However, the application of Laser Powder Bed Fusion (LPBF) Ti-6Al-4V alloy for structurally critical load-bearing components is limited. One of the main limiting factors affecting the structural integrity, are manufacturing defects. Additionally, the high cooling rates associated with LPBF process result in the formation of large residual stress (RS) with complex fields. Such RS can cause cracking and geometrical distortions of the part even right after production. Also, the microstructure of LPBF Ti-6Al-4V in the as-built condition is significantly different from that of the conventionally produced alloy. All these factors affect the mechanical behavior of the material. Therefore, to improve the material performance it is important to evaluate the individual effect of RS, defects, and microstructure on fatigue life. To this aim Ti-6Al-4V LPBF material in as-built condition and subjected to different post-processing, including two heat treatments (for stress relief and microstructural modification) and Hot Isostatic Pressing (HIP, for densification), were investigated. Prior to Low Cycle Fatigue (LCF) tests at operating temperature (300°C), the microstructure (phases, crystallographic texture, and grain morphology), the mesostructure (defect shape and distribution), and subsurface RS on the LCF samples were investigated. It was found that the fatigue performance of HIPped samples is similar to that of conventionally produced Ti-6Al-4V. The tensile RS found at the surface of as-built samples decreased the fatigue life compared to heat-treated samples. Additionally, the modification of the microstructure (by heat treatment) did not affect the fatigue performance in the regime of mostly elastic strain. This shows that in the absence of tensile RS the manufacturing defects solely control the failure of LPBF components and densification has the strongest effect on the improvement of the mechanical performance. T2 - ASTM ICAM 2020 CY - Online meeting DA - 16.11.2020 KW - Additive manufacturing KW - Ti-6Al-4V KW - Computed tomography KW - Residual stress PY - 2020 AN - OPUS4-51695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, K. A1 - Rehmer, Birgit A1 - Avila, Luis A1 - Haubrich, J. A1 - Serrano Munoz, Itziar A1 - Requena, G. A1 - Bruno, Giovanni T1 - Separation of the impact of residual stress and microstructure on the fatigue performance of LPBF Ti-6Al-4V at elevated temperature (Keynote) N2 - Ti-6Al-4V alloy is intensively used in the aerospace industry because of its high specific strength. However, the application of Laser Powder Bed Fusion (LPBF) Ti-6Al-4V alloy for structurally critical load-bearing components is limited. One of the main limiting factors affecting the structural integrity, are manufacturing defects. Additionally, the high cooling rates associated with LPBF process result in the formation of large residual stress (RS) with complex fields. Such RS can cause cracking and geometrical distortions of the part even right after production. Also, the microstructure of LPBF Ti-6Al-4V in the as-built condition is significantly different from that of the conventionally produced alloy. All these factors affect the mechanical behavior of the material. Therefore, to improve the material performance it is important to evaluate the individual effect of RS, defects, and microstructure on fatigue life. To this aim Ti-6Al-4V LPBF material in as-built condition and subjected to different post-processing, including two heat treatments (for stress relief and microstructural modification) and Hot Isostatic Pressing (HIP, for densification), were investigated. Prior to fatigue tests at elevated temperature, the microstructure, the mesostructure, and subsurface RS on the fatigue samples were investigated. It was found that the fatigue performance of HIPped samples is similar to that of conventionally produced Ti-6Al-4V. The tensile RS found at the surface of as-built samples decreased the fatigue life compared to heat-treated samples. Additionally, the modification of the microstructure (by heat treatment) did not affect the fatigue performance in the regime of mostly elastic strain. This shows that in the absence of tensile RS the manufacturing defects solely control the failure of LPBF components and densification has the strongest effect on the improvement of the mechanical performance. T2 - EUROMAT 2021 CY - Online meeting DA - 12.09.2021 KW - Additive manufacturing KW - Ti-6Al-4V KW - Residual stress KW - Fatigue performance PY - 2021 AN - OPUS4-53278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Artzt, K. A1 - Rehmer, Birgit A1 - Haubrich, J. A1 - Avila, Luis A1 - Schoenstein, F. A1 - Serrano Munoz, Itziar A1 - Requena, G. A1 - Bruno, Giovanni T1 - Separation of the impact of residual stress and microstructure on the fatigue performance of LPBF Ti-6Al-4V at elevated temperature N2 - Manufacturing defects, high residual stress (RS), and microstructures affect the structural integrity of laser powder bed fusion (LPBF) Ti-6Al-4V. In this study, the individual effect of these factors on fatigue performance at elevated temperature (300 °C) was evaluated. Material in as-built condition and subjected to post-processing, including two heat treatments and hot isostatic pressing, was investigated. It was found that in the absence of tensile RS, the fatigue life at elevated temperature is primary controlled by the defects; and densification has a much stronger effect than the considered heat treatments on the improvement of the mechanical performance. KW - Additive manufacturing KW - Ti-6Al-4V KW - Residual stress KW - Fatigue performance KW - Computed tomography PY - 2021 U6 - https://doi.org/10.1016/j.ijfatigue.2021.106239 SN - 0142-1123 VL - 148 SP - 106239 PB - Elsevier Ltd. AN - OPUS4-52369 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -