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 T2 - Proceedings ECNDT2018 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 T2 - Proceedings ECNDT2018 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 JF - Materials Science & Engineering A 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 DO - 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 JF - Metallurgical and materials transactions A 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 DO - 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 - 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 JF - Materials Performance & Characterization 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 DO - 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) JF - Strain 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 DO - 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 T2 - Residual stresses 2018, ECRS-10 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 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-466053 SN - 978-1-9452-9188-3 SN - 978-1-9452-9189-0 DO - https://doi.org/10.21741/9781945291890-30 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 -