TY - CONF A1 - Kannengießer, Thomas A1 - Rhode, Michael T1 - Fügetechnik in Wasserstofftechnologien - Forschungsbedarf für die Branche N2 - Die Studie gibt einen kurzen Überblick über die jetzige Bedeutung der Fügetechnik in Wasserstofftechnologien und über zukünftige Forschungsbedarfe für die Branche in den einzelnen Technologiefeldern Wasserstofferzeu-gung, -speicherung, -transport und -nutzung. Fügetechnologien haben dabei wesentliche Bedeutung für die er-folgreiche Umsetzung von technischen Komponenten der Wasserstofftechnologien. Die Schwerpunkte bzw. For-schungsbedarfe ergeben sich bspw. durch die Erstellung neuer Infrastruktur für Wasserstoffspeicherung und -transport sowie durch Umnutzung der bestehenden Erdgasinfrastruktur. Bei der Wasserstofferzeugung und -anwendung wird z.B. die Entwicklung effiziente Massenproduktionsmethoden von Elektrolyseuren und Brennstoff-zellen einen wichtigen Meilenstein bilden und laserbasierte Fügetechnologien sind hier zum Teil schon etabliert. Die additive Fertigung nimmt dabei eine Querschnittsposition ein und besitzt hohes Anwendungspotential für die Zukunft z.B. für die Fertigung von Komponenten in Gasturbinen. Aus den technischen Fragestellungen und For-schungsbedarfen ergeben sich zudem Herausforderungen für die notwendige Neu- und Weiterentwicklung von technischen Regelwerken und Normen und den Eingang in die Aus- und Weiterbildung von fügetechnischem Fachpersonal. T2 - DVS Congress 2021 CY - Essen, Germany DA - 14.09.2021 KW - Wasserstoff KW - Fügetechnik KW - Forschung KW - Technologie PY - 2021 AN - OPUS4-53321 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus T1 - Adequate repair concepts for high-strength steel weld joints for offshore support structures considering design influences N2 - The sustainable and resource-efficient production of wind energy plants requires the use of modern high-strength fine-grain structural steels. This applies to both foundation and erection structures. During the assembly of steel structures, unacceptable defects can occasionally be found in the weld area. In most cases, the economical solution would be local thermal gouging of the affected areas and re-welding. Due to the high shrinkage restraint of the joint groove in the overall structure, the superposition of global and local welding-induced stresses may lead to crack formation and component failure, particularly in interaction with the degradation of the microstructure and mechanical properties of high-strength steels during the repair process [1]. Corresponding standards hardly provide any information on adequate repair concepts, and there is no uniform scientific data on which to base such concepts. In this study, several relevant findings are discussed based on examples of structural engineering focusing on mechanical-technological properties and residual stresses, e.g. [1]. Further experimental and numerical work as conducted by [2] and weld tests under defined restraint conditions in special weld test-setups [3] show that an optimization of the welding-induced stresses of high-strength structural steels is achievable by means of an adapted heat control. The present research involves systematic investigations of influences of shrinkage restraint, the number of repair cycles and heat control during repair welding of a recently available high-strength offshore steel S500MLO (EN 10225-1). A quantification of the shrinkage restraint of repair weld joints is achievable by means of restraint intensity concept [4], analogous to previous studies [5]. Using structural mechanics calculations, geometries of self-restrained specimens are identified representing different defined rigidity conditions of repair welds considering actual high-strength steel components. Welding experiments with DIC analyses (digital image correlation) of the occurring strains during welding and XRD analyses (X-ray diffraction) of the resulting residual stresses after welding and cooling show increasing transient loads and significantly elevated residual stress profiles in the weld area with increasing restraint intensity. Especially in the heat affected zone, tensile residual stresses of up to 80 % of the nominal yield strength occur when welding under increased restraint conditions. In relation to the presented existing results, this indicates that a safe repair welding is primarily achievable by means of appropriate repair concepts and heat control taking into account the high welding stresses and special microstructures of high-strength steels. Finally, the aim of this research is to derive recommendations for repair concepts appropriate to the stresses and materials involved providing a basis for standards and guidelines, especially for SMEs, in order to avoid damage and, in most cases, expensive reworking and to improve the full utilization of the potential of high-strength steels. T2 - 74th IIW Annual Assembly and International Conference, C II-A CY - Online meeting DA - 07.07.2021 KW - High-strength structural steels KW - Welding KW - Repair KW - Residual stresses KW - Restraint PY - 2021 AN - OPUS4-53320 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus T1 - Consideration of design influences to provide adequate repair concepts for high-strength steel weld joints in offshore support structures N2 - The sustainable and resource-efficient production of offshore wind turbines requires the use of modern high-strength fine-grained structural steels (Martin and Schroeter, 2005). This applies to wind turbines in terms of increasing turbine sizes as well as to maintenance and installation vessels and equipment (Ummenhofer et al., 2013). Without the demanded high load-bearing capacities and boom lengths, the economic realization of these goals would be inconceivable. During the assembly of high-strength steel structures, unacceptable defects can occasionally be found in the weld area, although the welding process was executed in accordance with the specifications. In most cases, the economical solution would be local thermal gouging of the affected areas and re-welding. Corresponding standards hardly provide any information on adequate repair concepts, and there is no uniform scientific data on which to base such concepts. This applies particularly to the consideration and optimization of welding-induced stresses due to the high shrinkage hindrance of the gouging grooves and degradation of the adjacent microstructures by gouging and re-welding. The result, especially in the case of high-strength steel grades, are frequently recurring imperfections as well as a missing consideration of the additionally induced welding stresses in the design of the structure. In this context, at BAM component-relevant investigations focused on welding residual stress evolution and microstructural degradation during repair of weld joints due to local thermal gouging and re-welding are carried out within the scope of a FOSTA project (P1311, IGF 20162N). In this study, several relevant findings are discussed based on examples of structural engineering focusing on mechanical-technological properties and residual stresses, for instance found by (Schasse, 2017). Also experimental and numerical work as conducted by (Wongpanya, 2008) and weld tests under defined shrinkage restraint in special weld test-setups for research projects, e. g. FOSTA-P922 (Kannengiesser and Schroepfer, 2015) and P1011 (Kannengiesser and Schroepfer, 2017) have shown that an optimization of the welding-induced stresses of high-strength structural steels is specifically achievable by means of adapted heat control concepts (Schroepfer, 2017). The present research involves systematic investigations of influences of shrinkage restraint, the number of repair cycles and heat control during repair welding of the relatively new developed offshore-relevant high-strength steel S500MLO (EN 10225-1). For the quantification of the shrinkage restraint of weld joints, the concept of restraint intensity established by (Satho et al., 1973) was applied analogous to recent research, e. g. (Schwenk et al., 2008). By means of structural mechanics calculations, geometries of self-strained specimens were identified, that represent different defined rigidity conditions of repair welds of real components, cf. Fig. 1. It could be shown that with increasing weld joint restraint intensity significantly higher residual stresses in the weld metal and heat affected zone up to 80 % of the nominal yield strength occur, cf. Fig. 2. In relation to existing results, it has been shown that a safe repair of such welds can only be achieved by means of appropriate repair concepts and heat control taking the high welding stresses and special microstructures of high-strength steels into account. Finally, the aim of this research is to derive recommendations for repair concepts appropriate to the stresses and materials involved providing a basis for standards and guidelines, especially for SMEs, in order to avoid damage and, in most cases, expensive reworking and to improve the full utilization of the potential of high-strength steels. T2 - Wind Energy Science Conference 2021 CY - Online meeting DA - 25.05.2021 KW - High-strength structural steels KW - Welding KW - Repair KW - Residual stresses KW - Restraint PY - 2021 AN - OPUS4-53319 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus T1 - Konstruktive Einflüsse bei der beanspruchungsgerechten Reparatur geschweißter Bauteile aus hochfesten Feinkornbaustählen N2 - Bei der Montage von Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. Die Verarbeitungsregelwerke empfehlen das lokale thermische Ausfugen betroffener Bereiche und erneutes Schweißen, geben aber aufgrund fehlender wissenschaftlich fundierter Untersuchungen kaum Informationen zu adäquaten Reparaturkonzepten. Dies betrifft insbesondere die Berücksichtigung und Optimierung resultierender schweißbedingter Beanspruchungen durch hohe Schrumpfbehinderungen der Ausfugenuten sowie der Gefügedegradation angrenzender Bereiche durch das Ausfugen und erneute Schweißen. Gerade bei hochfesten Stahlgüten ergeben sich dadurch häufig reduzierte mechanische Eigenschaften und zusätzliche schweißbedingte Beanspruchungen sowie erneut auftretende Nahtdefekte. Deshalb sind für das Forschungsvorhaben systematische bauteilrelevante Untersuchungen der schweißbedingten Beanspruchungen und Gefügeveränderungen reparierter Schweißnähte in Abhängigkeit von der Schrumpfbehinderung und Wärmeführung beim Schweißen und Ausfugen sowie von der Reparaturzyklenanzahl geplant, mit dem Ziel Empfehlungen für beanspruchungs- und werkstoffgerechte Reparaturkonzepte abzuleiten. Hierfür sind gerade Analysen an hochfesten Stahlgüten S500 für den Offshore-Bereich und S960QL für den Mobilkranbau interessant, die zur Errichtung und Fertigung hocheffizienter Konstruktionen wie Windenergieanlagen notwendig sind. Die Erkenntnisse bieten eine Grundlage für entsprechende Normen und Regelwerke. Damit können letztlich Schäden und zumeist teure Nacharbeiten verhindert und eine verbesserte Ausnutzung des hohen Festigkeitspotentials hochfester Stähle erreicht werden. Gerade auch KMU können mit Blick auf die Kosten für Fertigung, Schweißarbeit und Material von den Erkenntnissen beim Einsatz hochfester Stähle, die für eine effiziente Realisierung der Energiewende in Deutschland notwendig sind, profitieren. T2 - Bachelor-, Master-, Doktoranden-Kolloquium der Otto-von-Guericke Universität Magdeburg CY - Online meeting DA - 17.06.2021 KW - Eigenspannungen KW - Hochfest KW - Feinkornbaustahl KW - Reparatur KW - Schweißen PY - 2021 AN - OPUS4-53318 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus T1 - Beanspruchungsgerechte Reparatur beim Bauteilschweißen hochfester Feinkornbaustähle N2 - Eine nachhaltige und ressourceneffiziente Fertigung und Errichtung von Windenergieanlagen, sowohl auf See als auch an Land, erfordert zunehmend den Einsatz moderner hochfester Feinkornbaustähle. Werden nach dem Schweißen dieser hochfesten Konstruktionen unzulässige Defekte detektiert, sind nach geltenden Verarbeitungsrichtlinien die defekten Bereiche durch lokales Ausfugen und anschließendes Schweißen zu reparieren. Fehlende Informationen zu adäquaten Reparaturkonzepten in den Regelwerken bedingen oftmals eine unzureichende Berücksichtigung dabei auftretender zusätzlicher Beanspruchungen durch die erhöhte Schrumpfbehinderung der Ausfugenuten. Zusätzlich haben die ausführenden Betriebe vielfach kaum Kenntnis über die Degradation angrenzender Gefüge durch thermische Ausfugeprozesse und erneutes Schweißen, die in diesem Zusammenhang besonders bei den hochfesten Stählen als kritisch anzusehen sind. Das aktuelle Forschungsvorhaben der BAM (FOSTA P1311/IGF-Nr.20162N) fokussiert hierfür systematisch bauteilrelevante Untersuchungen zu den schweißbedingten Beanspruchungen und Gefügeveränderungen bei der Reparatur von hochfesten Schweißverbindungen. Wesentlich sind hierbei der Einfluss der Schrumpfbehinderung, der Wärmeführung beim Schweißen und Ausfugen sowie der Reparaturzyklenanzahl und die metallurgischen Aspekte bei den hochfesten Güten S500MLO für zukünftige Offshore-Anwendungen und S960QL für aktuelle Mobilkrananwendungen. Aufbauend auf einigen Studien zur schweißbedingten Beanspruchung hochfester Stähle zeigt der vorliegende Beitrag die Identifikation geeigneter Probengeometrien und Schweißdetails mittels numerischer und experimenteller Analysen. Dadurch wird die Übertragbarkeit der vorgestellten Schweißexperimente und Ergebnisse hinsichtlich der resultierenden Schweißeigenspannungen auf reale Reparaturfälle im Bereich des hochfesten Stahlbaus sichergestellt. Es zeigt sich in Übereinstimmung mit früheren Ergebnissen eine signifikante Erhöhung der Beanspruchungen an den variierten schlitzförmigen Prüfnähten. Das Eigenspannungsniveau sowohl im Schweißgut als auch in der WEZ korreliert mit dem Einspanngrad. Mit dem Ziel beanspruchungs- und werkstoffgerechte Reparaturkonzepte zu erarbeiten, sind zum einen geringere Wärmeinbringungen, besonders durch niedrige Zwischenlagentemperaturen und Einspannbedingungen anzustreben, um hohe Beanspruchungen und kritische Gefügedegradationen im Reparaturbereich zu vermeiden. Dies wird durch systematische Untersuchungen zum Ausfugen und Schweißen sowie letztlich dem Transfer von Verarbeitungsempfehlungen für die Anwender und Richtlinien erreicht. T2 - DVS Congress 2021 CY - Essen, Germany DA - 14.09.2021 KW - Eigenspannungen KW - Hochfest KW - Feinkornbaustahl KW - Reparatur KW - Schweißen PY - 2021 AN - OPUS4-53317 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus T1 - Berücksichtigung konstruktiver Einflüsse für die beanspruchungsgerechte Reparatur hochfester Schweißverbindungen N2 - Bei der Montage von Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. Die Verarbeitungsregelwerke empfehlen das lokale thermische Ausfugen betroffener Bereiche und erneutes Schweißen, geben aber aufgrund fehlender wissenschaftlich fundierter Untersuchungen kaum Informationen zu adäquaten Reparaturkonzepten. Dies betrifft insbesondere die Berücksichtigung und Optimierung resultierender schweißbedingter Beanspruchungen durch hohe Schrumpfbehinderungen der Ausfugenuten sowie der Gefügedegradation angrenzender Bereiche durch das Ausfugen und erneute Schweißen. Gerade bei hochfesten Stahlgüten ergeben sich dadurch häufig reduzierte mechanische Eigenschaften und zusätzliche schweißbedingte Beanspruchungen sowie erneut auftretende Nahtdefekte. Deshalb sind für das Forschungsvorhaben systematische bauteilrelevante Untersuchungen der schweißbedingten Beanspruchungen und Gefügeveränderungen reparierter Schweißnähte in Abhängigkeit von der Schrumpfbehinderung und Wärmeführung beim Schweißen und Ausfugen sowie von der Reparaturzyklenanzahl geplant, mit dem Ziel Empfehlungen für beanspruchungs- und werkstoffgerechte Reparaturkonzepte abzuleiten. Hierfür sind gerade Analysen an hochfesten Stahlgüten S500 für den Offshore-Bereich und S960QL für den Mobilkranbau interessant, die zur Errichtung und Fertigung hocheffizienter Konstruktionen wie Windenergieanlagen notwendig sind. Die Erkenntnisse bieten eine Grundlage für entsprechende Normen und Regelwerke. Damit können letztlich Schäden und zumeist teure Nacharbeiten verhindert und eine verbesserte Ausnutzung des hohen Festigkeitspotentials hochfester Stähle erreicht werden. Gerade auch KMU können mit Blick auf die Kosten für Fertigung, Schweißarbeit und Material von den Erkenntnissen beim Einsatz hochfester Stähle, die für eine effiziente Realisierung der Energiewende in Deutschland notwendig sind, profitieren. T2 - NA 092-00-05 GA (DVS AG Q 4/Q 4.1) CY - Online meeting DA - 10.03.2021 KW - Eigenspannungen KW - Gefügedegradation KW - Hochfester Feinkornbaustahl KW - Reparatur KW - Schweißen KW - Wärmeführung PY - 2021 AN - OPUS4-53316 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Evans, Alexander A1 - Mishurova, Tatiana A1 - Sprengel, Maximilian A1 - Pirling, T. A1 - Kromm, Arne A1 - Bruno, Giovanni T1 - The importance of subsurface residual stress in laser powder bed fusion IN718 N2 - The residual stress (RS) in laser powder bed fusion (LPBF) IN718 alloy samples produced using a 67°-rotation scan strategy is investigated via laboratory X-ray diffraction (XRD) and neutron diffraction (ND). The location dependence of the strain-free (d₀) lattice spacing in ND is evaluated using a grid array of coupons extracted from the far-edge of the investigated specimen. No compositional spatial variation is observed in the grid array. The calculated RS fields show considerable non-uniformity, significant stress gradients in the region from 0.6 to 2 mm below the surface, as well as subsurface maxima that cannot be accounted for via XRD. It is concluded that failure to determine such maxima would hamper a quantitative determination of RS fields by means of the stress balance method. KW - Laser powder bed fusion KW - Neutron and X-ray diffraction KW - Residual stress analysis KW - Strain-free lattice references KW - Stress balance PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-532707 DO - https://doi.org/10.1002/adem.202100895 SN - 1615-7508 SN - 1527-2648 VL - 24 IS - 6 SP - 1 EP - 7 PB - Wiley-VCH CY - Weinheim AN - OPUS4-53270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Tim T1 - Characterization of Hydrogen Diffusion in a Thick-walled Submerged Arc Multi-Layer Weld Joint N2 - The energy production of the future will be dominated by CO2-emission free techniques like wind turbines and become essential in scope of the planned hydrogen economy. As onshore installation capacity is limited, the in-crease of the number of offshore wind turbines (OWT) is a major goal. In that connection, the OWTs continuously increase in size and weight and demand adequate foundations concepts like monopiles or tripods. These compo-nents are typically manufactured from welded mild steel plates with thickness up to 200 mm. The predominant welding technique is submerged arc welding (SAW) with up to five wires. In accordance with the standards, the occurrence of delayed hydrogen assisted cracking is anticipated by either a hydrogen removal heat treatment (HRHT) or a so-called minimum waiting time (MWT) before non-destructive testing (NDT) of the respective weld joint is allowed. The reason for the MWT is the necessary time for the hydrogen diffusion at ambient temperature due the high plate thickness. Both the effectiveness of a HRHT at elevated temperatures or the MWT at ambient temperature can be estimated by calculation of the diffusion time. This time depends on reliable hydrogen diffu-sion coefficients and these are rare in literature. For that reason, this study presents the hydrogen diffusion coef-ficients obtained from a multi-layer SAW joint of an offshore steel grade. Two different experimental techniques were used to identify the respective diffusion behavior: (1) hydrogen desorption experiments with a carrier gas hot extraction analyzer at elevated temperatures for the characterization of a HRHT and (2) the electrochemical permeation technique at ambient temperature for the characterization of an MWT. From both experiments, the respective diffusion coefficients were calculated. The obtained DCs are different from those reported in literature, i.e., the duration or applicability of a HRHT or MWT must be critically discussed. T2 - European Congress and Exhibition on Advanced Materials and Process - Euromat 2021 CY - Online meeting DA - 13.09.2021 KW - Welding KW - Offshore KW - Wind turbine KW - Hydrogen KW - Cracking PY - 2021 AN - OPUS4-53296 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sprengel, Maximilian T1 - The relaxation of macroscopic residual stresses in laser powder bed fused stainless steel 316L N2 - The processing of stainless steel 316L using the additive manufacturing process Laser Powder Bed Fusion (LPBF) can widen its field of application due to a strong increase in Yield strength, without making major compromises on the ductility nor its outstanding corrosion and oxidation properties. Furthermore, improved designs that either reduce the weight or optimise the function of a part can be obtained using LPBF. These benefits are however counterbalanced by the proneness of LPBF to inducing high Residual Stresses (RS) during manufacturing. The characterisation and monitoring of these RS are of paramount importance for the wider acceptance of the LPBF process. This study focuses on the relaxation of the initial macroscopic RS present in an LPBF 316L as-built prism that undergoes various routes of manufacturing steps to achieve different specimen geometries and stress relieving treatments. The RS are determined using Angle-Dispersive (AD) and Time-of-Flight (TOF) neutron diffraction. The results reveal high tensile RS close to the surfaces and compressive RS near the centre of the as-built parts. The reduction in size and change of geometry heavily impact the stress ranges of the remaining RS, with lower stress ranges in cylindrical shaped compared to rectangular shaped specimens. Also, the application of different stress relieving heat treatments showed that heat-treating temperatures above 800 °C are necessary to obtain a strong relaxation in LPBF 316L. T2 - The second European Conference on the Structural Integrity of Additively Manufactured Materials CY - Online meeting DA - 08.09.2021 KW - Residual Stress KW - Additive Manufacturing KW - Neutron Diffraction PY - 2021 AN - OPUS4-53263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Quackatz, Lukas T1 - Measurement of hydrogen concentration in steels by laser-induced breakdown spectroscopy (LIBS) N2 - Current efforts to achieve lightweight construction and the required reduction in CO2 emissions and an increase in energy and resource efficiency call for the increasing use of high-strength fine-grain structural steels. However, as the strength of higher-strength fine-grain structural steels increases, so do the associated joining challenges. Particular attention must be paid to hydrogen-assisted cold cracking. The influence of hydrogen reveals itself less in the strength but has a significant effect on the deformability [1, 2]. The degradation of the material properties can lead to zero ductility, where the values of the yield strengths coincide with the tensile strengths. Laser-induced breakdown spectroscopy (LIBS) is a spectroscopic technique that can be used to determine elemental compositions without pre-treatment of the samples. Short, high-energy laser pulses ablate a small volume (< 0.1 mm3) of the examined material and ionize it to form a plasma. The decaying plasma emits element-specific light. This light is spectroscopically analysed and allows to detect qualitatively the present elements and to quantify them with help of a standardization routine. The simple experimental set-up and the fast, nearly non-destructive analysis procedure characterize the LIBS analysis. The LIBS method allows a time and spatially resolved in situ measurement of steel components in use. Even low hydrogen concentrations (~ 1 wt.-ppm) in steel can be measured with the LIBS method and can be quantified with help of certified reference materials. The results are compared with results gained with the well-established carrier gas hot extraction method. T2 - MaterialsWeek 2021 CY - Online Meeting DA - 07.09.2021 KW - LIBS KW - Hydrogen KW - Stainless steel KW - Diffusion PY - 2021 AN - OPUS4-53234 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bergant, M. A1 - Werner, Tiago A1 - Madia, Mauro A1 - Yawny, A. A1 - Zerbst, Uwe T1 - Short crack propagation analysis and fatigue strength assessment of additively manufactured materials: An application to AISI 316L N2 - This paper presents the application of short crack propagation models based on the cyclic R-curve for assessing the fatigue strength of additively manufactured (AM) materials containing fabrication defects. Chapetti’s and IBESS models were implemented in combination with Murakami’s √area parameter, considering recently published data on laser powder bed fusion processed AISI 316L stainless steels. Estimated S-N curves and Kitagawa-Takahashi diagrams predict fairly well the experimental data, especially the origin of the failure from internal or surface defects. These results provide an indication that the methods based on the cyclic R-curve constitute suitable tools for fatigue behavior assessment of AM materials. KW - AM 316L stainless steel KW - Cyclic R-curve KW - Chapetti’s and IBESS model KW - S-N curve KW - Kitagawa-Takahashi diagram PY - 2021 DO - https://doi.org/10.1016/j.ijfatigue.2021.106396 VL - 151 PB - Elsevier Ltd. AN - OPUS4-53082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schork, B. A1 - Zerbst, Uwe A1 - Kiyak, Yusuf A1 - Kaffenberger, M. A1 - Madia, Mauro A1 - Oechsner, M. T1 - Effect of the parameters of weld toe geometry on the FAT class as obtained by means of fracture mechanics-based simulations N2 - The fracture mechanics-based IBESS approach is applied to the determination of FAT classes of butt welds with crack Initiation along the weld toe. The aim is an investigation of the effect of the geometrical parameters toe radius, flank angle, reinforcement and secondary notches such as roughness or undercuts. The influence of these parameters is discussed both individually and in combination; however, excluding statistical distributions of them and the material data. The results, when compared with conventional FAT classes for butt welds, are encouraging with respect to a potential contribution of IBESS to the discussion of more advanced quality criteria for welds. To that purpose, demands for further research are proposed. KW - Fracture mechanics KW - Weld toe geometry KW - Fatigue crack initiation KW - FAT class approach PY - 2020 DO - https://doi.org/10.1007/s40194-020-00874-7 IS - 64 SP - 925 EP - 936 PB - Springer AN - OPUS4-53079 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baeßler, Matthias A1 - Kannengießer, Thomas T1 - Aktivitäten in Forschung und Zulassung im Bereich Windenergie N2 - Die vielfältigen Tätigkeiten der BAM im Bereich technischer Sicherheit von Windenergieanlagen werden vorgestellt und im Bereich aktueller Entwicklungen in der Fügetechnik detailliert. T2 - Arbeitskreis Gründungsstrukturen und Stahlbau der WAB CY - Online meeting DA - 13.04.2021 KW - BAM Windenergie Fügetechnik PY - 2021 AN - OPUS4-53026 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Investigation on the influence of different testing methods and parameters on the determination of fatigue crack growth data N2 - The correct determination of fatigue crack propagation data is of great importance for the damage tolerance design of engineering components, especially with regard to the calculation of residual lifetime and the establishment of inspection intervals. The fatigue crack propagation threshold Δ𝐾th, in this respect, is a crucial input parameter for simulating crack growth, since it corresponds to the stress intensity factor range at which a non-growing crack starts to propagate. However, the experimental determination of Δ𝐾th, as well as its application, is still confronted with few issues related among others to the load ratio (R) dependency of Δ𝐾th, the testing procedure, and environmental effects. These can lead to large scatter and significant errors in the prediction of component failure. In this context, the use of the intrinsic fatigue crack propagation threshold Δ𝐾th,eff in component assessment is a promising alternative, since it does not depend on a number of factors that affect Δ𝐾th, but only on the elastic properties (𝐸-modulus) and the lattice (Burger’s vector ‖𝑏‖) of the material. The aim of the present work is therefore to investigate different experimental procedures for the determination of Δ𝐾th,eff, namely: (a) conventional load reduction (LR) procedures, (b) the 𝐾max procedure and (c) compression pre-cracking load reduction and constant amplitude (respectively CPLR and CPCA) methods. Furthermore, the determination of Δ𝐾th has been carried out varying some testing parameters, such as test frequency, Δ𝐾 at the beginning of the crack propagation test (Δ𝐾0) and stress ratio (R). The results are statistically analyzed and a discussion about the use of Δ𝐾th and Δ𝐾th,eff for the component fatigue assessment is presented. T2 - 6th. International Virtual Conference of Engineering Against Failure CY - Online meeting DA - 23.06.2021 KW - Crack closure KW - Damage tolerance assessment KW - Residual lifetime KW - Intrinsic fatigue crack propagation threshold PY - 2021 AN - OPUS4-52899 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Zerbst, Uwe A1 - Madia, Mauro ED - Yadroitsev, I. ED - Yadroitsava, I. ED - Du Plessies, A. ED - McDonald, E. T1 - Structural integrity II: fatigue properties N2 - If a component is cyclically loaded, its load carrying capacity is considerably lower than in the monotonic loading case. This general observation applies in particular to L-PBF parts. The causes of this are mainly material defects such as pores and unwelded regions (Chapter 8) and a pronounced surface roughness in the as-built condition (Chapter 9). In addition, effects due to the anisotropy of the microstructure (Chapter 6) and a complex residual stress pattern (Chapter 7) play an important role. A consequence is that common strategies of fatigue assessment cannot be transferred to L-PBF applications without modifications. Due to the inhomogeneity of the material, the determination of representative material properties and the transfer to the component is a problem, and this is also the case with regard to the consideration of defects, surface roughness and residual stresses. The chapter gives a brief introduction to these problem areas. KW - Fatigue crack propagation stagesdefects KW - Fatigue strength KW - Fatigue life KW - Fracture mechanics PY - 2021 SN - 978-0-12-824090-8 DO - https://doi.org/10.1016/B978-0-12-824090-8.00015-9 SP - 377 EP - 394 PB - Elsevier Inc. CY - Amsterdam ET - 1 AN - OPUS4-52854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina T1 - Untersuchung des Erweichungsmechanismus beim Schweißen in der Wärmeeinflusszone mikrolegierter hochfester Stähle N2 - Für eine signifikante Festigkeitssteigerung von vergüteten hochfesten Feinkornbaustählen ist eine Zugabe von Mikrolegierungselementen wie Nb und Ti unerlässlich. Die Normvorgaben zur chemischen Zusammensetzung dieser Stähle gibt sehr breite Legierungsintervalle für die Hersteller vor, was eine Vorhersage bezüglich der Schweißeignung und des Tragverhaltens der Schweißverbindung erschwert. Zuzüglich kommen vermehrt moderne Schweißprozesse zum Einsatz, die durch ihre hohe Wärmeeinwirkung die Phasenumwandlung in der Wärmeeinflusszone negativ beeinflussen können. Eine unerwünschte Eigenschaft ist dabei die Erweichung (Festigkeitsverlust, engl.: softening) dieser Wärmeeinflusszone. T2 - BMDK CY - Online meeting DA - 17.06.2021 KW - WEZ-Erweichung KW - Vergüteter hochfester Feinkornbaustahl KW - Modifizierter Sprühlichtbogen KW - ThermoCalc KW - HAZ-Softening KW - MAG-Schweißen PY - 2021 AN - OPUS4-52846 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Quackatz, Lukas T1 - In situ Untersuchung der Phasenverteilung und der Schmelzbaderstarrung von Duplexstählen mittels laserinduzierter Plasmaspektroskopie (LIPS) N2 - Schweißprozesse von nichtrostenden Duplexstählen verursachen aufgrund hoher Abkühlungsraten und Änderungen der chemischen Zusammensetzung ein unausgewogenes Austenit (γ)/Ferrit (δ)-Verhältnis. Das verursacht eine Degradation der mechanischen Eigenschaften und der Korrosionsbeständigkeit. Die In-situ-Überwachung des Schweißbades soll mit Hilfe der laserinduzierten Plasmaspektroskopie (LIPS) realisiert werden. Ein großer Vorteil dieser Technik ist die hochgenaue zeit- und ortsaufgelöste Messung der chemischen Zusammensetzung während des Schweißens. Bisherige Untersuchungen haben ergeben, dass die LIBS-Methode geeignet ist, chemische Elemente während des Schweißens zu detektieren und eine Verteilung ausgewählter Elemente aufzuzeigen. Chemische Zusammensetzungen können mit vorab erstellten Kalibrierkurven dargestellt weerden. T2 - BMDK der Universität Magdeburg CY - Online Meeting DA - 17.06.2021 KW - LIBS KW - In situ KW - Duplex stainless steel KW - TIG welding PY - 2021 AN - OPUS4-52823 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander 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 - JOUR A1 - Zerbst, Uwe A1 - Bruno, Giovanni A1 - Buffière, J.-Y. A1 - Wegener, T. A1 - Niendorf, T. A1 - Wu, T. A1 - Zhang, X. A1 - Kashaev, N. A1 - Meneghetti, G. A1 - Hrabe, Nik A1 - Madia, Mauro A1 - Werner, Tiago A1 - Hilgenberg, Kai A1 - Koukolikova, M. A1 - Prochazka, R. A1 - Dzugan, J. A1 - Möller, B. A1 - Beretta, S. A1 - Evans, Alexander A1 - Wagener, R. A1 - Schnabel, K. T1 - Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges N2 - This article is an outcome of a workshop on Fatigue of Additive Manufactured Metallic Components jointly organized by the Federal Institute for Materials Research and Testing (BAM) Berlin, Germany and the National Institute of Standards and Technology (NIST) Boulder, CO, U.S.A. The aim of the workshop was a comprehensive discussion of the specific aspects of additively manufactured (AM) components in regard to failure under cyclic loading. Undoubtedly, a better understanding and the further development of approaches for damage tolerant component design of AM parts are among the most significant challenges currently facing the use of these new technologies. This article presents a thorough overview of the workshop discussions. It aims to provide a review of the parameters affecting the damage tolerance of AM parts with special emphasis on the process parameters intrinsic to the AM technologies, the resulting defects and residual stresses. Based on these aspects, concepts for damage tolerant component design for AM are reviewed and critically discussed. KW - Additive manufacturing KW - Fatigue loading KW - Component assessment KW - Damage tolerance KW - Defects KW - Residual stresses PY - 2021 DO - https://doi.org/10.1016/j.pmatsci.2021.100786 SN - 0079-6425 VL - 121 PB - Elsevier CY - Amsterdam AN - OPUS4-51937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Der Schwellenwert der da/dN-∆K-Kurve als Auslegungskriterium für die Bauteilbewertung N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung ∆Kth und dem sich anschließenden Schwellenwertbereich der da/dN-∆K-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - Tagung Werkstoffprüfung 2020 CY - Online meeting DA - 03.12.2020 KW - Schadenstolerante Bauteilauslegung, KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Restlebensdauer PY - 2020 DO - https://doi.org/10.48447/WP-2020-025 SP - 1 EP - 8 AN - OPUS4-52788 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Schröder, Nina A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Hydrogen-assisted cracking in GMA welding of high-strength structural steel - A new look into this issue at narrow groove N2 - Modern arc processes, such as the modified spray arc (Mod. SA), have been developed for gas metal arc welding of high-strength structural steels with which even narrow weld seams can be welded. High-strength joints are subjected to increasingly stringent requirements in terms of welding processing and the resulting component performance. In the present work, this challenge is to be met by clarifying the influences on hydrogen-assisted cracking (HAC) in a high-strength structural steel S960QL. Adapted samples analogous to the self-restraint TEKKEN test are used and analyzed with respect to crack formation, microstructure, diffusible hydrogen concentration and residual stresses. The variation of the seam opening angle of the test seams is between 30° and 60°. To prevent HAC, the effectiveness of a dehydrogenation heat treatment (DHT) from the welding heat is investigated. As a result, the weld metals produced at reduced weld opening angle show slightly higher hydrogen concentrations on average. In addition, increased micro- as well as macro-crack formation can be observed on these weld metal samples. On all samples without DHT, cracks in the root notch occur due to HAC, which can be prevented by DHT immediately after welding. KW - High-strength structural steel KW - Gas metal arc welding KW - Diffusible hydrogen KW - Hydrogen-assisted cracking KW - TEKKEN KW - Residual stresses KW - Weld metal cracking PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527260 DO - https://doi.org/10.3390/met11060904 VL - 11 IS - 6 SP - 1 EP - 18 PB - MDPI CY - Basel AN - OPUS4-52726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sprengel, Maximilian T1 - Towards the optimization of post laser powder bed fusion stress relieve treatments of stainless steel 316L N2 - The formation of high magnitude residual stresses is inherent in laser powder bed fused processed austenitic steel 316L. Post-process heat treatments to relieve these stresses are necessary. In this study, heat treatment temperatures of 450°C, 800°C and 900°C were applied in order to avoid excessive sensitization. This temperature range thereby encompassed the upper and lower bounds for stress relieving treatment of this material. The residual stresses were determined by neutron diffraction and the evolution of the microstructure was monitored using scanning electron microscopy and electron backscattered diffraction. The results show that a full relaxation of the residual stresses is achieved when applying 900°C for 1 hour, which seems to be closely related to the dissolution of the subgrain solidification cellular structure. T2 - 2nd Workshop on In-situ Monitoring and Microstructure Development in Additive Manufacturing CY - Online meeting DA - 19.04.2021 KW - Residual Stress KW - Additive Manufacturing KW - Steel PY - 2021 AN - OPUS4-52709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa A1 - Zerbst, Uwe A1 - Madia, Mauro T1 - Vergleichende Untersuchungen zum intrinsischen Schwellenwert der da/dN-ΔK-Kurve N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung, Δ𝐾𝑡ℎ, und dem sich anschließenden Schwellenwertbereich der 𝑑𝑎𝑑𝑁⁄−Δ𝐾-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - 53. Tagung des DVM-Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 18.02.2021 KW - Schadenstolerante Bauteilauslegung, Restlebensdauer, intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung PY - 2021 SN - 2366-4797 SP - 211 EP - 220 PB - Deutscher Verband für Materialforschung und -prüfung e.V. (DVM) CY - Berlin AN - OPUS4-52704 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Ulbricht, Alexander A1 - Fritsch, Tobias A1 - Mishurova, Tatiana A1 - Kromm, Arne A1 - Hofmann, M. A1 - Wimpory, R. C. A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts N2 - The influence of scan strategy on the residual stress (RS) state of an as-built IN718 alloy produced by means of laser powder bed fusion (LPBF) is investigated. Two scan vector rotations (90°-alternation and 67°-rotation), each produced following two different scan vector lengths (long and short), are used to manufacture four rectangular prisms. Neutron diffraction (ND) and laboratory X-ray diffraction (XRD) techniques are used to map the bulk and surface RS state, respectively. The distortion induced upon removal from the baseplate is measured via profilometry. XRD measurements show that the two long scan vector strategies lead to higher RS when compared with the equivalent short scan vector strategies. Also, the 67°-rotation strategies generate lower RS than their 90°-alternation counterparts. Due to the lack of reliable stress-free d0 references, the ND results are analyzed using von Mises stress. In general, ND results show significant RS spatial non-uniformity. A comparison between ND and distortion results indicates that the RS component parallel to the building direction (Z-axis) has a predominant role in the Z-displacement. The use of a stress balance scheme allows to discuss the d0 variability along the length of the specimens, as well as examine the absolute RS state. KW - As-built LPBF IN718 alloy KW - Scan strategy influence KW - Neutron diffraction KW - Residual stress state KW - Stress balance condition KW - Distortion PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-526360 DO - https://doi.org/10.1002/adem.202100158 VL - 23 IS - 7 SP - 158 PB - Wiley AN - OPUS4-52636 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Short fatigue crack propagation in additively manufactured stainless steel 316L N2 - Fracture mechanics is a key to fatigue assessment in AM metal components. Short fatigue cracks are initiated at defects and pronounced surface roughness intrinsic to AM. The subsequent crack-propagation is strongly influenced by microstructural interactions and the build-up of crack-closure. The aim of the present study is to give an insight into short-crack propagation in AM-metals. Fatigue crack propagation resistance curves were determined experimentally for AISI 316L manufactured by Laser Powder Bed Fusion (L-PBF) which was heat treated at three different temperatures. Differences in the build-up of the fatigue-crack propagation threshold in between the L-PBF specimens and compared to wrought material are due to the residual stress states, a pronounced roughness of the crack-faces in the L-PBF specimens and phase transformation in the vicinity of the crack-tip, resulting in increased crack-closure. This, together with crack-branching found along the crack path, enhances the resistance to the propagation of fatigue cracks. T2 - In-situ Monitoring and Microstructure Development in Additive Manufactured Alloys CY - Online meeting DA - 19.04.2021 KW - AM KW - Cyclic R-Curve KW - Fatigue Crack Propagation PY - 2021 AN - OPUS4-52587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Bruno, Giovanni A1 - Hilgenberg, Kai T1 - Towards a Methodology for Component Design of Metallic AM Parts Subjected to Cyclic Loading N2 - The safe fatigue design of metallic components fabricated by additive manufacturing (AM) is still a largely unsolved problem. This is primarily due to (a) a significant inhomogeneity of the material properties across the component; (b) defects such as porosity and lack of fusion as well as pronounced surface roughness of the asuilt components; and (c) residual stresses, which are very often present in the as‐built parts and need to be removed by post‐fabrication treatments. Such morphological and microstructural features are very different than in conventionally manufactured parts and play a much bigger role in determining the fatigue life. The above problems require specific solutions with respect to the identification of the critical (failure) sites in AM fabricated components. Moreover, the generation of representative test specimens characterized by similar temperature cycles needs to be guaranteed if one wants to reproducibly identify the critical sites and establish fatigue assessment methods taking into account the effect of defects on crack initiation and early propagation. The latter requires fracture mechanics‐based approaches which, unlike common methodologies, cover the specific characteristics of so‐called short fatigue cracks. This paper provides a discussion of all these aspects with special focus on components manufactured by laser powder bed fusion (L‐PBF). It shows how to adapt existing solutions, identifies fields where there are still gaps, and discusses proposals for potential improvement of the damage tolerance design of L‐PBF components KW - L‐PBF KW - Fatigue KW - Fracture KW - Defects PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525822 DO - https://doi.org/10.3390/met11050709 VL - 11 IS - 5 SP - 709 PB - MDPI CY - Basel AN - OPUS4-52582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus T1 - Konstruktive Einflüsse bei der beanspruchungsgerechten Reparatur geschweißter Bauteile aus hochfesten Feinkornbaustählen N2 - Für eine nachhaltige und ressourceneffiziente Fertigung von Windkraftanlagen ist der Einsatz moderner hochfester Feinkornbaustähle vielfach notwendig. Bei der Montage hochfester Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. Derzeitige Normen und Verarbeitungsrichtlinien geben hierbei kaum Informationen zu adäquaten Reparaturkonzepten, insbesondere für hochfeste Stähle. Vor diesem Hintergrund werden an der Bundesanstalt für Materialforschung und -prüfung (BAM) bauteilrelevante Untersuchungen zu den schweißbedingten Beanspruchungen und Gefügeveränderungen bei der schweißtechnischen Reparatur durch lokales thermisches Ausfugen und erneutes Schweißen durchgeführt. Hierzu werden einige wesentliche Ergebnisse an Beispielen des Ingenieurbaus, mit Blick auf die mechanisch-technologischen Eigenschaften und Eigenspannungen erörtert. In einem aktuellen Vorhaben (FOSTA P1311, IGF 20162N) sind darauf aufbauend die Einflüsse durch die Schrumpfbehinderung und Wärmeführung beim Reparaturschweißen hochfester Feinkornbaustähle (S500MLO, S960QL) sowie die Reparaturzyklenanzahl Fokus systematischer Untersuchungen. Mittels strukturmechanischer Berechnungen ließen sich hierzu selbstbeanspruchende Probenformen identifizieren, die unterschiedliche definierte Steifigkeitsverhältnisse von Reparaturschweißnähten realer Bauteile abbilden. Schweißnähte an diesen bauteilähnlichen Proben weisen signifikant erhöhte schweißbedingte Beanspruchungen mit zunehmenden (Biege-)Einspanngraden auf. Im Vergleich mit bisherigen Erkenntnissen wird gezeigt, dass eine sichere Reparatur solcher Schweißnähte nur mittels optimaler Reparaturkonzepte und Wärmeführung gelingt, um diesen hohen Beanspruchungen und auch den speziellen Gefügen hochfester Stähle Rechnung zu tragen. Ziel der Untersuchungen ist es letztlich, Empfehlungen für beanspruchungs- und werkstoffgerechte Reparaturkonzepte gerade für KMU abzuleiten, um Schäden und zumeist teure Nacharbeiten zu vermeiden. T2 - 4. Niedersächsisches Symposium Materialtechnik CY - Online meeting DA - 25.02.2021 KW - Feinkornbaustähle KW - Hochfest KW - Reparaturschweißen KW - Eigenspannungen PY - 2021 AN - OPUS4-52562 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Treutler, K. A1 - Börner, Andreas A1 - Gustus, R. A1 - Kannengießer, Thomas A1 - Wesling, V. A1 - Maus-Friedrichs, W. T1 - Surface finishing of hard-to-machine cladding alloys for highly stressed components N2 - The supply and processing of materials for highly stressed components are usually cost-intensive. Efforts to achieve cost and resource efficiency lead to more complex structures and contours. Additive manufacturing steps for component repair and production offer significant economic advantages. Machining needs to be coordinated with additive manufacturing steps in a complementary way to produce functional surfaces suitable for the demands. Regarding inhomogeneity and anisotropy of the microstructure and properties as well as production-related stresses, a great deal of knowledge is still required for efficient use by small- and medium-size enterprises, especially for the interactions of subsequent machining of these difficult-to-machine materials. Therefore, investigations on these influences and interactions were carried out using a highly innovative cost-intensive NiCrMo alloy (IN725). These alloys are applied for claddings as well as for additive component manufacturing and repair welding using gas metal arc welding processes. For the welded specimens, the adequate solidification morphology, microstructure and property profile were investigated. The machinability in terms of finishing milling of the welded surfaces and comparative analyses for ultrasonic-assisted milling processes was examined focussing on surface integrity. It was shown that appropriate cutting parameters and superimposed oscillating of the milling tool in the direction of the tool rotation significantly reduce the mechanical loads for tool and workpiece surface. This contributes to ensure a high surface integrity, especially when cutting has to be carried out without cooling lubricants. KW - WAAM KW - IN725 KW - Machining KW - Ultrasonic-assisted milling KW - Residual stresses KW - Cutting forces KW - Surface integrity KW - Microstructure PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524872 DO - https://doi.org/10.1007/s00170-021-06815-y VL - 114 IS - 5-6 SP - 1427 EP - 1442 PB - Springer AN - OPUS4-52487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Rhode, Michael A1 - Wimpory, R. C. A1 - Kannengießer, Thomas T1 - Influence of welding stresses on relief cracking during heat treatment of a creep-resistant 13CrMoV steel: Part III - Assessment of residual stresses from small-scale to real component welds N2 - For higher operational temperatures and pressures required in petrochemical plants, the modified 13CrMoV9-10 steel was developed providing high resistance against creep and compressed hydrogen. Extreme care during the welding procedure is necessary for this steel, attributed to low toughness, high strength in as-welded state, and increased susceptibility to stress relief cracking (SRC) during post-weld heat treatment (PWHT). Previous research of SRC in creep-resistant steels discussed mainly thermal and metallurgical factors. Few previous findings addressed the influences of welding procedure on crack formation during PWHT considering real-life manufacturing conditions. These investigations focus on effects of welding heat control on stresses during welding and subsequent PWHT operations close to realistic restraint and heat dissipation conditions using a special 3D testing facility, which was presented in parts I and II of this contribution. Part III addresses investigations on residual stress evolution affecting crack formation and discusses the transferability of results from large-scale testing to laboratory-scale. Experiments with test set-ups at different scales under diverse rigidity conditions and an assessment of the residual stresses of the weld-specimens using X-ray (surface near) and neutron diffraction analysis (bulk) were performed. This study aims to provide a way of investigating the SRC behaviour considering component-specific residual stresses via small-scale testing concepts instead of expensive weld mock-ups. KW - Welding KW - Creep-resistant steel KW - Residual stresses KW - Post-weld heat treatment KW - Stress relief cracking PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-524403 DO - https://doi.org/10.1007/s40194-021-01101-7 SN - 1878-6669 VL - 65 SP - 1671 EP - 1685 PB - Springer CY - Berlin AN - OPUS4-52440 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eissel, A. T1 - Modification of CoCr alloys to optimize of additively welded microstructures and subsequent surface finishing N2 - Due to increasing requirements relating to the efficiency of highly stressed components in turbine or plant construction, the use of cost-intensive, difficult to process materials is increasingly necessary today. In this context, cobalt-chromium alloys in particular are highly resistant to thermal and mechanical stress, as well as to corrosive and abrasive loads. Moreover, increasingly complex structures and the optimisation of resource efficiency also require additive manufacturing steps for the production or repair of components in many sectors. In order to realise a homogeneous and isotropic microstructure, alloy modifications are made to the alloy CoCr26Ni9Mo5W. For this purpose, hafnium and zirconium are added at 1 % and 0,33 % by mass each, as these elements are supposed to have a positive effect on the microstructure morphology. Plasma-Transferred-Arc is used for the welding tests. Wall structures are welded by multiple single-layer, overlapping welding beads on low-alloyed steel substrate (S355). The results show that the alloying elements hafnium and zirconium have a clear influence on the microstructure. Hardness measurements were also carried out. With each modification, the hardness is increased compared to the original material. The machining analyses show a reduction in cutting forces using ultrasonic assisted milling for high cutting speed and low feed rate. T2 - 2021 Intermediate meeting of C IX NF CY - Online meeting DA - 09.03.2021 KW - Alloy modification KW - Ultrasonic-assisted milling KW - Plasma-Transferred-Arc KW - Filler metal modification KW - Additive manufacturing PY - 2021 AN - OPUS4-52356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eissel, A. T1 - Analysen zur Beeinflussung von Gefüge und Fertigungsbeanspruchungen bei der Generation, Reparatur und Bearbeitung hochbelasteter Komponenten Kurzvorstellung des DVS Vorhabens 1.3211 (20.979N) N2 - Das DVS-Vorhaben 01.3211 „Herstellung beanspruchungsgerechter Oberflächen durch Kombination innovativer additiver und abtragender Fertigungsschritte an hochbelasteten Komponenten“ ist ein Kooperationsprojekt der Bundesanstalt für Materialforschung und -prüfung (BAM) und dem Institut für Schweißtechnik und Trennende Fertigungsverfahren (ISAF) der Technischen Universität Clausthal. Das Übergeordnete Projektziel ist das Erlangen von Erkenntnissen für eine sichere und wirtschaftliche, kombinierte additive und abtragende Fertigung aus kostenintensiven Werkstoffen hochbelasteter Komponenten insbesondere für KMU. Dabei stehe die beiden Werkstoffe CoCr26Ni9Mo5W (2.4681) und FeNi36 (1.3912) im Fokus. Mittels Modifikation der Schweißzusätze sind homogen und isotrop ausgeprägte Werkstoffeigenschaften und eine Erhöhung der Prozessstabilität und Fertigungsfreiheitsgrade bei der additiven Fertigung erzielbar. Darüber hinaus wird der Einfluss nachfolgender abtragender Bearbeitungsschritte des ultraschallunterstützen und des konventionellen Fräsprozesses untersucht. Die ersten Ergebnisse der Mikrostruktur sowie der Härte der via PTA gefertigten Probenkörper des CoCr-Werkstoffes und den ersten Modifizierungen werden vorgestellt. Darüber hinaus wird ein Ausblick auf die folgenden Arbeiten gegeben. T2 - Gemeinschaftssitzung DIN/DVS NAS 092-00-05 GA "Zerstörende Prüfung von Schweißverbindungen" CY - Online meeting DA - 10.03.2021 KW - Legierungsmodifikation KW - Ultraschallunterstütztes Fräsen KW - Plasma-Pulver-Auftragschweißen KW - Schweißzusatzmodifikation KW - Schlichtfräsen PY - 2021 AN - OPUS4-52352 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madia, Mauro T1 - Damage Tolerant Approach in Additively Manufactured Metallic Materials N2 - Damage tolerance counts as one of the most widespread approach to fatigue assessment and surely as one of the most promising in understanding the process-structure-property-performance relationships in additively manufactured metallic materials. Manufacturing defects, surface roughness, microstructural features, short and long crack fatigue propagation, residual stresses and applied loads can be taken into consideration in a fracture mechanics-based fatigue assessment. Many aspects are crucial to the reliable component life prediction. Among those a prominent role is played by an accurate measurement and modelling of the short crack fatigue behavior, and reliable statistical characterization of defects and residual stresses. This work aims at addressing the issues related to both experimental testing, fatigue and fatigue crack propagation, and fracture mechanics-based modelling of fatigue lives. Examples will be provided on an additively manufactured AISI 316 L. T2 - TMS2021 VIRTUAL CY - Online meeting DA - 15.03.2021 KW - AISI 316L KW - Additive Manufacturing KW - Damage Tolerance KW - Microstructure KW - Defects KW - Residual Stress PY - 2021 AN - OPUS4-52293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Vergleichende Untersuchungen zum intrinsischen Schwellenwert der da/dN-∆K Kurve N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung, Δ𝐾𝑡ℎ, und dem sich anschließenden Schwellenwertbereich der 𝑑𝑎𝑑𝑁⁄−Δ𝐾-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - DVM-Arbeitskreis „Bruchmechanik und Bauteilsicherheit“ 2021 CY - Online meeting DA - 18.02.2021 KW - Schadenstolerante Bauteilauslegung KW - Restlebensdauer KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung PY - 2021 AN - OPUS4-52263 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Experimentelle Ermittlung zyklischer R-Kurven in additiv gefertigtem AISI 316L Stahl N2 - Diese Untersuchung beschäftigt sich mit der Charakterisierung von Kurzrisswachstum in mittels Laser-Pulverbett-Verschmelzen (LPBF - Laser Powder Bed Fusion) hergestelltem rostfreien austenitischen Stahl. Spezifischer wird die Ermittlung zyklischer R-Kurven untersucht. Diese beschreiben den Aufbau des Widerstands gegen Ermüdungsrisswachstum - d.h. des Schwellenwertes - aufgrund von Rissschließeffekten bei physikalisch kurzen Rissen. Mit Hilfe der zyklischen R-Kurven kann die Fähigkeit eines Bauteils, physikalisch kurze Risse zu arretieren, charakterisiert werden. Wir verfügen damit über eine Schnittstelle zwischen klassischer Ermüdung und Bruchmechanik. Das ist gerade auch für additiv gefertigte (AM – Additive Manufacturing) Materialien von Interesse. Diese weisen prozessintrinsische Defekte auf, die als Initiierungsstellen kurzer Ermüdungsrisse agieren. Im Rahmen der experimentellen Untersuchungen wurden zyklische R-Kurven für konventionellen und LPBF AISI-316L-Stahl ermittelt. Insbesondere wurde der Einfluss verschiedener Wärmebehandlungen (WB1: 450°C, WB2: 800°C und WB3: 900°C) auf das Wachstumsverhalten physikalisch kurzer Risse im LPBF-Material untersucht. Aufgrund hoher Eigenspannungen war die Ermittlung des Kurzrisswachstumsverhaltens bei WB1 nicht möglich. Für WB2 und WB3 ergaben sich sehr unterschiedliche zyklische R-Kurven. Untersuchungen der Eigenspannungen, der Bruchfläche (insbesondere der Rauheit) und der Mikrostruktur sollen die Ursachen für das unterschiedliche Verhalten erklären. Die Ergebnisse werden mit den Verhältnissen in konventionellem Material verglichen. T2 - Tagung des Arbeitskreises Bruchmechanik und Bauteilsicherheit CY - Online meeting DA - 18.02.2021 KW - Additive Manufacturing KW - Zyklische R-Kurve KW - Ermüdungsriss KW - L-PBF KW - 316L PY - 2021 AN - OPUS4-52250 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thomas, Maximilian T1 - Digitalisierung in der Heißrissprüfung - Wie viel Information steckt in einer MVT-Probe? N2 - Die im MVT-Test standardmäßig erfasste Gesamtrisslänge erlaubt keine direkten Rückschlüsse auf die Heißrissanfälligkeit des untersuchten Werkstoffs. Der vorliegende Beitrag erläutert, inwiefern aus der Morphologie von Oberflächenrissen an MVT-Proben dennoch auf das Werkstoffverhalten geschlossen werden kann. T2 - Jährl. Sitzung des DIN/DVS Normenausschuss 092-00-05 GA CY - Online meeting DA - 10.03.2021 KW - MVT KW - Varestraint KW - Heißriss KW - Erstarrungsriss PY - 2021 AN - OPUS4-52243 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eissel, A. A1 - Engelking, Lorenz T1 - Bericht zum Fortschritt des laufenden Projekts: „Herstellung beanspruchungsgerechter Oberflächen durch Kombination innovativer additiver und abtragender Fertigungsschritte an hochbelasteten Komponenten“ N2 - Das DVS-Vorhaben 01.3211 „Herstellung beanspruchungsgerechter Oberflächen durch Kombination innovativer additiver und abtragender Fertigungsschritte an hochbelasteten Komponenten“ ist ein Kooperationsprojekt der Bundesanstalt für Materialforschung und -prüfung (BAM) und dem Institut für Schweißtechnik und Trennende Fertigungsverfahren (ISAF) der Technischen Universität Clausthal. Das Übergeordnete Projektziel ist das Erlangen von Erkenntnissen für eine sichere und wirtschaftliche, kombinierte additive und abtragende Fertigung aus kostenintensiven Werkstoffen hochbelasteter Komponenten insbesondere für KMU. Dabei stehen die beiden Werkstoffe CoCr26Ni9Mo5W (2.4681) und FeNi36 (1.3912) im Fokus. Mittels Modifikation der Schweißzusätze sind homogen und isotrop ausgeprägte Werkstoffeigenschaften und eine Erhöhung der Prozessstabilität und Fertigungsfreiheitsgrade bei der additiven Fertigung erzielbar. Darüber hinaus wird der Einfluss nachfolgender abtragender Bearbeitungsschritte des ultraschallunterstützen und des konventionellen Fräsprozesses untersucht. Die mit dem Forschungsvorhaben verbundenen Nutzen für KMU sind die Stärkung der Innovationsfähigkeit und der Wirtschaftlichkeit sowie die Erhöhung der Wettbewerbsfähigkeit. In AP-1 wurden erste Zerspanversuche am CoCr-Ausgangswerkstoff durchgeführt. Ziel der Versuche war in erster Linie die Identifikation geeigneter Fräswerkzeuge und -parameter. In AP-2 wurden erste Legierungsmodifikationen des CoCr-Ausgangswerkstoffes durchgeführt und die Mikrostruktur sowie die Härte analysiert. T2 - Sitzung des Fachausschusses 01 „Schweißmetallurgie und Werkstoffverhalten“ CY - Online meeting DA - 17.02.2021 KW - DVS KW - Legierungsmodifikation KW - Ultraschallunterstützter Fräsprozess KW - Additive Fertigung KW - Fortschrittsbericht PY - 2021 AN - OPUS4-52179 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonego, M. A1 - Madia, Mauro A1 - Eder, M. A1 - Fleck, C. A1 - Pessan, L. A. T1 - Microstructural features influencing the mechanical performance of the Brazil nut (Bertholletia excelsa) mesocarp N2 - Brazil nut (Bertholletia excelsa) fruits are capable of resisting high mechanical forces when released from trees as tall as 50 m, as well as during animal dispersal by sharp-teethed rodents. Thick mesocarp plays a crucial part in seed protection. We investigated the role of microstructure and how sclereids, fibers, and voids affect nutshell performance using compression, tensile and fracture toughness tests. Fractured specimens were analyzed through scanning electron microscopy (SEM) and microtomography (microCT). Mesocarp showed high deformability (strain at max. stress of ~30%) under compression loading, a critical tensile strength of ~24.9 MPa, a Weibull modulus of ~3, and an elastic modulus of ~2 GPa in the tensile test. The fracture toughness, estimated through the work of fracture of SENB tests, reached ~2 kJ/m2. The thick and strong walls of mesocarp cells, with a weaker boundary between them (compound middle lamella), promote a tortuous intercellular crack path. Several toughening mechanisms, such as crack deflection, breaking of fiber bundles, fiber pullout and bridging as well as crack branching, occur depending on how fiber bundles and voids are oriented. KW - Toughening mechanisms KW - Brazil nut Mesocarp KW - Microstructure KW - Mechanical properties PY - 2021 DO - https://doi.org/10.1016/j.jmbbm.2020.104306 VL - 116 SP - 104306 PB - Elsevier Ltd. AN - OPUS4-52081 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Fritsch, Tobias A1 - Mishurova, Tatiana A1 - Trofimov, Anton A1 - Apel, D. A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Hesse, René A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - On the interplay of microstructure and residual stress in LPBF IN718 N2 - The relationship between residual stresses and microstructure associated with a laser powder bed fusion (LPBF) IN718 alloy has been investigated on specimens produced with three different scanning strategies (unidirectional Y-scan, 90° XY-scan, and 67° Rot-scan). Synchrotron X-ray energy-dispersive diffraction (EDXRD) combined with optical profilometry was used to study residual stress (RS) distribution and distortion upon removal of the specimens from the baseplate. The microstructural characterization of both the bulk and the nearsurface regions was conducted using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). On the top surfaces of the specimens, the highest RS values are observed in the Y-scan specimen and the lowest in the Rot-scan specimen, while the tendency is inversed on the side lateral surfaces. A considerable amount of RS remains in the specimens after their removal from the baseplate, especially in the Y- and Z-direction (short specimen Dimension and building direction (BD), respectively). The distortion measured on the top surface following baseplate thinning and subsequent removal is mainly attributed to the amount of RS released in the build direction. Importantly, it is observed that the additive manufacturing microstructures challenge the use of classic theoretical models for the calculation of diffraction elastic constants (DEC) required for diffraction-based RS analysis. It is found that when the Reuß model is used for the calculation of RS for different crystal planes, as opposed to the conventionally used Kröner model, the results exhibit lower scatter. This is discussed in context of experimental measurements of DEC available in the literature for conventional and additively manufactured Ni-base alloys. KW - L-PBF IN718 material KW - Effect of scanning strategies KW - Near-surface X-ray diffraction KW - Residual stress in AM KW - Distortion upon baseplate removal PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-519460 DO - https://doi.org/10.1007/s10853-020-05553-y SN - 0022-2461 VL - 56 IS - 9 SP - 5845 EP - 5867 PB - Springer AN - OPUS4-51946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Mishurova, Tatiana A1 - Fritsch, Tobias A1 - Serrano-Munoz, Itziar A1 - Kromm, Arne A1 - Haberland, C. A1 - Portella, Pedro Dolabella A1 - Bruno, Giovanni T1 - Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing N2 - Laser based powder bed fusion additive manufacturing offers the flexibility to incorporate standard and userdefined scan strategies in a layer or in between the layers for the customized fabrication of metallic components. In the present study, four different scan strategies and their impact on the development of microstructure, texture, and residual stresses in laser powder bed fusion additive manufacturing of a nickel-based superalloy Inconel 718 was investigated. Light microscopy, scanning electron microscopy combined with electron backscatter diffraction, and neutron diffraction were used as the characterization tools. Strong textures with epitaxially grown columnar grains were observed along the build direction for the two individual scan strategies. Patterns depicting the respective scan strategies were visible in the build plane, which dictated the microstructure development in the other planes. An alternating strategy combining the individual strategies in the successive layers and a 67◦ rotational strategy weakened the texture by forming finer microstructural features. Von Mises equivalent stress plots revealed lower stress values and gradients, which translates as lower distortions for the alternating and rotational strategies. Overall results confirmed the scope for manipulating the microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing by effectively controlling the scan strategies. KW - Additive manufacturing KW - Laser powder bed fusion KW - Nickel-based superalloys KW - Scan strategies KW - Residual stresses KW - Microstructure and texture PY - 2021 DO - https://doi.org/10.1016/j.addma.2020.101792 VL - 38 SP - 1792 PB - Elsevier B.V. AN - OPUS4-51944 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 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-518759 DO - https://doi.org/10.1016/j.addma.2020.101672 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 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 - Duarte, Larissa T1 - Der Schwellenwert der da/dN-∆K-Kurve als Auslegungskriterium für die Bauteilbewertung N2 - Für die Bestimmung der Restlebensdauer zyklisch beanspruchter Bauteile kommt dem Schwellenwert für Ermüdungsrissausbreitung ΔKth und dem sich anschließenden Schwellenwertbereich der dadN⁄-ΔK-Kurve große Bedeutung zu. Dem stehen Unsicherheiten bei der Bestimmung und Analyse gegenüber. Der Aufsatz befasst sich mit der Ermittlung des sogenannten intrinsischen Schwellenwerts, der als robuster Eingangsparameter für eine „rissschließfreie“ Analyse der Restlebensdauer von entscheidender Bedeutung ist. T2 - Tagung Werkstoffprüfung 2020 CY - Online meeting DA - 03.12.2020 KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Schadenstolerante Bauteilauslegung KW - Restlebensdauer PY - 2020 AN - OPUS4-51754 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - García-González, M. A1 - Blasón Gonzalez, Sergio A1 - García-García, I. A1 - Lamela-Rey, M. J. A1 - Fernández-Canteli, A. A1 - Álvarez-Arenal, Á. T1 - Optimized planning and evaluation of dental implant fatigue testing: A specific software application N2 - Mechanical complications in implant-supported fixed dental prostheses are often related to implant and prosthetic design. Although the current ISO 14801 provides a framework for the evaluation of dental implant mechanical reliability, strict adherence to it may be difficult to achieve due to the large number of test specimens which it requires as well as the fact that it does not offer any probabilistic reference for determining the endurance limit. In order to address these issues, a new software program called ProFatigue is presented as a potentially powerful tool to optimize fatigue testing of implant-supported prostheses. The present work provides a brief description of some concepts such as load, fatigue and stress-number of cycles to failure curves (S-N curves), before subsequently describing the current regulatory situation. After analyzing the two most recent versions of the ISO recommendation (from 2008 and 2016), some limitations inherent to the experimental methods which they propose are highlighted. Finally, the main advantages and instructions for the correct implementation of the ProFatigue free software are given. This software will contribute to improving the performance of fatigue testing in a more accurate and optimized way, helping researchers to gain a better understanding of the behavior of dental implants in this type of mechanical test. KW - Dental materials KW - Prostheses KW - Implants KW - Reference standards KW - Software KW - Cyclic loading KW - Fatigue KW - Lifetime KW - S-N curve KW - Staircase method PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-516268 DO - https://doi.org/10.3390/biology9110372 SN - 2079-7737 VL - 9 IS - 11 SP - 372-1 EP - 372-12 PB - MDPI CY - Basel AN - OPUS4-51626 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Duarte, Larissa T1 - Ermittlung des intrinsischen Schwellenwerts und dessen Validierung als Werkstoffparameter N2 - Die schadenstolerante Bewertung von zyklisch beanspruchten Bauteilen auf bruchmechanischer Grundlage ist von großer praktischer Bedeutung, insbesondere für die Spezifizierung von Inspektionsintervallen. Eine Schwachstelle der gegenwärtigen Vorgehensweise bildet der nur ungenügend verstandene Schwellenwertbereich der da/dN-ΔK -Kurve. Relevant ist das deshalb, weil viele Bauteile bei Lasten betrieben werden, die in eben diesen Bereich fallen. Der Vortrag beschäftigt sich mit Unsicherheiten bei der Ermittlung des Schwellenwertes, mit Einflussparametern, die dabei zu berücksichtigen sind, und mit einem Vorschlag zur konservativen Einbeziehung des Schwellenwertbereichs in die Bauteilauslegung. Der Schwellenwert gegen Ermüdungsrissausbreitung ist als der zyklische Spannungsintensitätsfaktor definiert, unterhalb dessen kein Risswachstum mehr stattfindet. Dabei ist zu beachten, dass der Wert in der konventionellen da/dN-ΔK -Kurve auf Langrisswachstum beschränkt ist und, strenggenommen, auch das nur dann, wenn das Rissschließphänomen voll ausgebildet ist. Unter Rissschließen versteht man das Schließen des zyklisch beanspruchten Risses in der Regel oberhalb des Nulldurchgangs der Last. Wichtige Rissschließmechanismen sind das plastizitäts-, das rauheits- und das oxid-induzierte Schließen wobei die beiden letztgenannten im Schwellenwertbereich dominierend sind. Der Schwellenwert selbst besteht aus zwei Anteilen, einem intrinsischen, der von den elastischen Konstanten und vom Gittertyp abhängt und einem extrinsischen, der mit dem Aufbau der Rissschließeffekte zusammenhängt und von Parametern wie der Mikrostruktur, dem Spannungsverhältnis aus Unter- und Oberlast und der Risstiefe beeinflusst wird. In Fällen, bei denen oxid-induziertes Rissschließen eine Rolle spielt, hängt der erhaltene Wert des Schwellenwerts vom experimentellen Verfahren ab, wobei die konventionelle Lastabsenkung nach Standard nicht-konservative Werte ergeben kann. Der Vortrag thematisiert die unterschiedlichen Optionen der experimentellen Ermittlung mit besonderem Fokus auf dem intrinsischen Schwellenwert und, davon ausgehend, die Anbindung an den rissschließkorrigierten Paris-Bereich der da/dN-ΔK -Kurve. T2 - Werkstoffmechanikseminar 2020 CY - Online meeting DA - 26.10.2020 KW - Intrinsischer Schwellenwert gegen Ermüdungsrissausbreitung KW - Schadenstolerante Bauteilauslegung KW - Restlebensdauer PY - 2020 AN - OPUS4-51604 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Short fatigue crack propagation in L-PBF 316L stainless steel N2 - Fracture mechanics is a key to fatigue assessment in AM metal components. Short fatigue cracks are initiated at defects and pronounced surface roughness intrinsic to AM. The subsequent crack-propagation is strongly influenced by microstructural interactions and the build-up of crack-closure. The aim of the present study is to give an insight into short-crack propagation in AM-metals. Fatigue crack propagation resistance curves were determined experimentally for AISI 316L manufactured by Laser Powder Bed Fusion (L-PBF) which was heat treated at three different temperatures. Differences in the build-up of the fatigue-crack propagation threshold in between the L-PBF specimens and compared to wrought material are due to the residual stress states, a pronounced roughness of the crack-faces in the L-PBF specimens and phase transformation in the vicinity of the crack-tip, resulting in increased crack-closure. This, together with crack-branching found along the crack path, enhances the resistance to the propagation of fatigue cracks. T2 - ASTM International Conference on Additive Manufacturing 2020 CY - Online meeting DA - 16.11.2020 KW - Additive Manufacturing KW - Cyclic R-Curve KW - Component assessment KW - L-PBF KW - 316L KW - Residual Stress KW - Fatigue Crack Growth PY - 2020 AN - OPUS4-51585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Kurzrisswachstum in additiv gefertigtem austenitischem Edelstahl 316L N2 - Diese Untersuchung beschäftigt sich mit der Charakterisierung von Kurzrisswachstum in mittels Laser-Pulverbett-Verschmelzen (LPBF - Laser Powder Bed Fusion) hergestelltem rostfreien austenitischen Stahl. Spezifischer wird die Ermittlung zyklischer R-Kurven untersucht. Diese beschreiben den Aufbau des Widerstands gegen Ermüdungsrisswachstum - d.h. des Schwellenwertes - aufgrund von Rissschließeffekten bei physikalisch kurzen Rissen. Mit Hilfe der zyklischen R-Kurven kann die Fähigkeit eines Bauteils, physikalisch kurze Risse zu arretieren, charakterisiert werden. Wir verfügen damit über eine Schnittstelle zwischen klassischer Ermüdung und Bruchmechanik. Das ist gerade auch für additiv gefertigte (AM – Additive Manufacturing) Materialien von Interesse. Diese weisen prozessintrinsische Defekte auf, die als Initiierungsstellen kurzer Ermüdungsrisse agieren. Im Rahmen der experimentellen Untersuchungen wurden zyklische R-Kurven für konventionellen und LPBF AISI-316L-Stahl ermittelt. Insbesondere wurde der Einfluss verschiedener Wärmebehandlungen (WB1: 450°C, WB2: 800°C und WB3: 900°C) auf das Wachstumsverhalten physikalisch kurzer Risse im LPBF-Material untersucht. Aufgrund hoher Eigenspannungen war die Ermittlung des Kurzrisswachstumsverhaltens bei WB1 nicht möglich. Für WB2 und WB3 ergaben sich sehr unterschiedliche zyklische R-Kurven. Untersuchungen der Eigenspannungen, der Bruchfläche (insbesondere der Rauheit) und der Mikrostruktur sollen die Ursachen für das unterschiedliche Verhalten erklären. Die Ergebnisse werden mit den Verhältnissen in konventionellem Material verglichen. T2 - 41. Werkstoffmechanikseminar TU Darmstadt CY - Online meeting DA - 26.10.2020 KW - AM KW - Additiv KW - Zyklische R-Kurve KW - 316L KW - Ermüdung KW - Ermüdungsrisswachstum KW - Risswachstum PY - 2020 AN - OPUS4-51603 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Influence of welding stresses on relaxation cracking during heat treatment of a creep-resistant 13CrMoV steel, Part III N2 - Efficiency and flexibility are currently a major concern in the design of modern power plants and chemical processing facilities. The high requirements for economic profitability and in particular climate change neutrality are driving this development. Consequently, plant equipment and chemical reactor components are designed for higher operating pressure and temperature. Creep-resistant CrMo steels had been used as constructional materials for decades but came to operational limitations, for example the resistance against so-called high-temperature hydrogen attack in petrochemical reactors. For that purpose, 20 years ago V-modified CrMo steels had been developed for use in the petrochemical industry due to their very good creep-strength and hydrogen pressure resistance at elevated temperatures enabling long service life of the respective components. For example, the 13CrMoV9-10 steel is applicable for process temperatures of up to 482 °C and hydrogen pressures of up to 34.5 MPa. Due to the large dimensions and wall thickness of the reactors (wall thickness up to 475 mm) and the special alloy concept, reliable weld manufacturing of the components is extremely challenging. First, low toughness and high strength of the weld joint in the as-welded condition are critical regarding weld cracking. High welding residual stresses are the result of the highly restrained shrinkage of the component welds. For this purpose, the entire component must be subjected to Post-Weld Heat Treatment (PWHT) after completion of the welding operation. The aim is to increase the toughness of the weld joints as well as to reduce the welding induced residual stresses. Before and during PWHT, extreme caution is required to prevent cracking. Unfortunately, V-modified CrMo steels possess an increased susceptibility to cracking during stress relaxation the so-called stress relief cracking (SRC). Available literature studies have largely focused on thermal and metallurgical factors. However, little attention has been paid on the influence of the welding procedure on crack formation during PWHT considering actual manufacturing conditions. For that reason, we investigated in our previous studies (part I and II), the influence of heat control on the mechanical properties by simulating actual manufacturing conditions prevailing during the construction of petrochemical reactors using a special 3D- acting testing facility. The focus of part I was put on the influence of the welding heat control on mechanical stresses and the effect on cracking during PWHT. Part II was mainly dedicated to the metallurgical causes of SRC during PWHT and the interaction with the occurring mechanical stresses. It could be shown that not only high welding-induced stresses due to increased weld heat input cause higher susceptibility for SRC formation. It was further intensified by an altered precipitation behaviour in presence of mechanical stresses that are caused by the component related restraint. The present part III shows how residual stresses, which are present in such welded components and significantly influence the crack formation, can be transferred to the laboratory scale. As a result, the effect on the residual stresses on the SRC behaviour can be evaluated on simplified small-scale specimens instead of expensive mock-ups. For this purpose, experiments with test set-ups at different scales and under different rigidity conditions were designed and carried out. T2 - IIW Annual Assembly, Meeting of Commission II-A CY - Online meeting DA - 20.07.2020 KW - Welding KW - Creep-resistant steel KW - Residual stresses KW - Post weld heat treatment KW - Stress relief cracking PY - 2020 AN - OPUS4-51587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Projektvorstellung FOSTA P1311: Beanspruchungsgerechte Reparatur von Schweiß-verbindungen bei der Fertigung von Bauteilen aushochfesten Feinkornbaustählen N2 - Bei der Montage von Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. Die Verarbeitungsregelwerke empfehlen das lokale thermische Ausfugen betroffener Bereiche und erneutes Schweißen, geben aber aufgrund fehlender wissenschaftlich fundierter Untersuchungen kaum Informationen zu adäquaten Reparaturkonzepten. Dies betrifft insbesondere die Berücksichtigung und Optimierung resultierender schweißbedingter Beanspruchungen durch hohe Schrumpfbehinderungen der Ausfugenuten sowie der Gefügedegradation angrenzender Bereiche durch das Ausfugen und erneute Schweißen. Gerade bei hochfesten Stahlgüten ergeben sich dadurch häufig reduzierte mechanische Eigenschaften und zusätzliche schweißbedingte Beanspruchungen sowie erneut auftretende Nahtdefekte. Deshalb sind für das Forschungsvorhaben systematische bauteilrelevante Untersuchungen der schweißbedingten Beanspruchungen und Gefügeveränderungen reparierter Schweißnähte in Abhängigkeit von der Schrumpfbehinderung und Wärmeführung beim Schweißen und Ausfugen sowie von der Reparaturzyklenanzahl geplant, mit dem Ziel Empfehlungen für beanspruchungs- und werkstoffgerechte Reparaturkonzepte abzuleiten. Hierfür sind gerade Analysen an hochfesten Stahlgüten S500 für den Offshore-Bereich und S960QL für den Mobilkranbau interessant, die zur Errichtung und Fertigung hocheffizienter Konstruktionen wie Windenergieanlagen notwendig sind. Die Erkenntnisse bieten eine Grundlage für entsprechende Normen und Regelwerke. Damit können letztlich Schäden und zumeist teure Nacharbeiten verhindert und eine verbesserte Ausnutzung des hohen Festigkeitspotentials hochfester Stähle erreicht werden. Gerade auch KMU können mit Blick auf die Kosten für Fertigung, Schweißarbeit und Material von den Erkenntnissen beim Einsatz hochfester Stähle, die für eine effiziente Realisierung der Energiewende in Deutschland notwendig sind, profitieren T2 - NA 092-00-05 GA (DVS AG Q 4/Q 4.1) CY - Hamm, Germany DA - 04.03.2020 KW - Reparatur KW - Eigenspannungen KW - Schweißen KW - Wärmeführung KW - Hochfester Feinkornbaustahl KW - Gefügedegradation PY - 2020 AN - OPUS4-51584 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Czeskleba, Denis T1 - Entwicklung von Wärmenachbehandlungskonzepten zur Vermeidung von spannungsrelaxationsrissen N2 - Vorstellung des Projekts Vh_9475 im Rahmen eines Kolloquiums der OVGU Magdeburg. In diesem Projekt wird erforscht, welchen Einfluss die PWHT-Parameter Aufheizrate und Haltetemperatur auf die Rissanfälligkeit von 13CrMoV9-10 haben. Diese Präsentation stellt den aktuellen Projektstand dar, gibt eine Übersicht über die Rissentstehung und wie die Forschungsstelle bei ihren Forschungen zu diesem Projekt vorgeht. Gleichzeitig wurde die Versuchstechnik vorgestellt und insbesondere die neue UP-Schweißanlage präsentiert. T2 - BMDK CY - Online meeting DA - 18.11.2020 KW - Spannungsrelaxationsrisse KW - 13CrMoV9-10 KW - PWHT KW - BMDK KW - Aufheizrate PY - 2020 AN - OPUS4-51583 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Rhode, Michael A1 - Yahyaoui, Hamza A1 - Kannengießer, Thomas ED - Lippold, J. ED - Böllinghaus, Thomas ED - Norrish, J. ED - Scotti, A. T1 - Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process N2 - High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used arc process is also important for the performance of the welded joint. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series withMod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A. KW - High-strength steel KW - GMA welding KW - Diffusible hydrogen KW - Implant test KW - Fractography PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515330 DO - https://doi.org/10.1007/s40194-020-00978-0 SN - 1878-6669 SN - 0043-2288 VL - 64 IS - 12 SP - 1997 EP - 2009 PB - Springer CY - Berlin Heidelberg AN - OPUS4-51533 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sprengel, Maximilian T1 - Using Neutron Diffraction to Monitor Stress Relaxation in Additively Manufactured 316L N2 - The relaxation of residual stress in laser powder bed fused stainless steel 316L parts was monitored using monochromatic and time-of-flight neutron diffraction. T2 - ISIS student meeting CY - Online meeting DA - 26.10.2020 KW - Stainless Steel KW - Residual Stress KW - Additive Manufacturing PY - 2020 AN - OPUS4-51469 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni A1 - Mishurova, Tatiana A1 - Serrano-Munoz, Itziar A1 - Ulbricht, Alexander A1 - Fritsch, Tobias A1 - Sprengel, Maximilian A1 - Evans, Alexander A1 - Kromm, Arne A1 - Madia, Mauro ED - Bruno, Giovanni T1 - A Critical Discussion on the Diffraction-Based Experimental Determination of Residual Stress in AM Parts N2 - As opposed to reviewing results on experimental determination of residual stress by diffraction, this paper discusses the open issues when dealing with residual stress determination in additive manufactured parts, in particular those manufactured with laser powder bed fusion techniques. Three points are addressed in detail: (a) the proper determination of the strain-free reference d0, (b) the problem of the determination of the principal axes, and (c) the use of the correct diffraction elastic constants. It is shown that all methods to determine the strain-free reference d0 suffer from caveats, and care must be taken in evaluating the most suitable for the problem being tackled. In addition, it is shown that, in some systems, the principal axes do correspond to the geometrical axes of the specimen, but this needs to be systematically checked, especially in the case of uni- or bidirectional hatching strategies. Finally, the need to experimentally determine the proper diffraction elastic constants is underlined, especially in the case of strongly textured specimens, which again depends on the deposition strategy. T2 - ASTM ICAM 2020 – ASTM International Conference on Additive Manufacturing CY - Online meeting DA - 16.11.2020 KW - Additive Manufacturing KW - Diffraction KW - Residual Stress PY - 2020 DO - https://doi.org/10.1520/STP163120190148 VL - STP1631 SP - 122 EP - 138 PB - ASTM International CY - USA AN - OPUS4-51347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR 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, M. 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. KW - Additive Manufacturing KW - Laser Powder Bed Fusion KW - LPBF KW - AISI 316L KW - Online Process Monitoring KW - Thermography KW - Residual Stress KW - Neutron Diffraction KW - X-ray Diffraction KW - Computed Tomography PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-512903 DO - https://doi.org/10.3390/met10091234 VL - 10 IS - 9 PB - MDPI CY - Basel AN - OPUS4-51290 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schaupp, Thomas A1 - Schröpfer, Dirk A1 - Schröder, Nina A1 - Kannengießer, Thomas T1 - Einfluss von Konstruktion und Wasserstoff auf die Kaltrissbildung hochfester Feinkornbaustähle N2 - Der konstruktive Leichtbau erfordert den zunehmenden Einsatz hochfester Feinkornbaustähle mit Streckgrenzen ≥ 690 MPa. Neben den durch die Wandstärkenreduzierung erreichbaren Einsparungen an Ressourcen und Fertigungszeit lässt sich eine weitere Minimierung der Schweißzeit und -kosten mittels abgesenkter Schweißnahtvolumina erreichen. Hierzu wurden moderne Lichtbogenprozesse, wie bspw. der modifizierte Sprühlichtbogen (Mod.SLB), mit erhöhter Abschmelzleistung entwickelt, mit denen auch enge Nahtspalte bzw. Nahtöffnungswinkel geschweißt werden können. Hochfeste Verbindungen unterliegen zunehmend erhöhten Anforderungen in Bezug auf die schweißtechnische Verarbeitung und der resultierenden Bauteilperformance und sicherheit. Dies gilt insbesondere beim Bauteilschweißen mittels solcher Hochleistungsverfahren in Verbindung mit engen Nahtspalten. In der vorliegenden Arbeit soll dieser Herausforderung durch Klärung der Einflüsse auf die Kaltrissbildung bei einem hochfesten Feinkornbau-stahl S960QL Rechnung getragen werden. Für die Kaltrissprüfung werden entsprechende adaptierte Proben analog dem selbstbeanspruchenden TEKKEN-Test verwendet und hinsichtlich Rissbildung, Gefüge, Gehalt an diffusiblem Wasserstoff und Eigenspannungen analysiert. Die Variation der Nahtöffnungswinkel der Prüfnähte erfolgt zwischen 30° und 60°. Zur Vermeidung wasserstoffunterstützter Kaltrissbildung wird die Wirksamkeit einer Nachwärmprozedur aus der Schweißwärme heraus untersucht. Als Ergebnis zeigen die Schweißgüter, die an reduziertem Nahtöffnungswinkel erzeugt wurden, im Mittel etwas höhere Wasserstoffkonzentrationen. Zudem ist an diesen Schweißgütern eine vermehrte Mikro- als auch Makrorissbildung festzustellen. An allen Proben, die nicht nachgewärmt wurden, treten Kerbrisse aufgrund von Kaltrissbildung auf, deren Vermeidung sich durch ein Nachwärmen unmittelbar nach dem Schweißen als besonders effektiv darstellte. T2 - DVS Congress 2020 - Große Schweißtechnische Tagung CY - Online meeting DA - 14.09.2020 KW - Hochfester Feinkornbaustahl KW - MAG-Schweißen KW - Kaltriss KW - Wasserstoff KW - TEKKEN PY - 2020 SN - 978-3-96144-098-6 VL - 365 SP - 564 EP - 570 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-51259 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schaupp, Thomas T1 - Einfluss von Konstruktion und Wasserstoff auf die Kaltrissbildung hochfester Feinkornbaustähle N2 - Der konstruktive Leichtbau erfordert den zunehmenden Einsatz hochfester Feinkornbaustähle mit Streckgrenzen ≥ 690 MPa. Neben den durch die Wandstärkenreduzierung erreichbaren Einsparungen an Ressourcen und Fertigungszeit lässt sich eine weitere Minimierung der Schweißzeit und -kosten mittels abgesenkter Schweißnahtvolumina erreichen. Hierzu wurden moderne Lichtbogenprozesse, wie bspw. der modifizierte Sprühlichtbogen (Mod.SLB), mit erhöhter Abschmelzleistung entwickelt, mit denen auch enge Nahtspalte bzw. Nahtöffnungswinkel geschweißt werden können. Hochfeste Verbindungen unterliegen zunehmend erhöhten Anforderungen in Bezug auf die schweißtechnische Verarbeitung und der resultierenden Bauteilperformance und sicherheit. Dies gilt insbesondere beim Bauteil-schweißen mittels solcher Hochleistungsverfahren in Verbindung mit engen Nahtspalten. In der vorliegenden Arbeit soll dieser Herausforderung durch Klärung der Einflüsse auf die Kaltrissbildung bei einem hochfesten Feinkornbaustahl S960QL Rechnung getragen werden. Für die Kaltrissprüfung werden entsprechende adaptierte Proben analog dem selbstbeanspruchenden TEKKEN-Test verwendet und hinsichtlich Rissbildung, Gefüge, Gehalt an diffusiblem Wasserstoff und Eigenspannungen analysiert. Die Variation der Nahtöffnungswinkel der Prüfnähte erfolgt zwischen 30° und 60°. Zur Vermeidung wasserstoffunterstützter Kaltrissbildung wird die Wirksamkeit einer Nachwärmprozedur aus der Schweißwärme heraus untersucht. Als Ergebnis zeigen die Schweißgüter, die an reduziertem Nahtöffnungs-winkel erzeugt wurden, im Mittel etwas höhere Wasserstoffkonzentrationen. Zudem ist an diesen Schweißgütern eine vermehrte Mikro- als auch Makrorissbildung festzustellen. An allen Proben, die nicht nachgewärmt wurden, treten Kerbrisse aufgrund von Kaltrissbildung auf, deren Vermeidung sich durch ein Nachwärmen unmittelbar nach dem Schweißen als besonders effektiv darstellte. T2 - DVS Congress - Große Schweißtechnische Tagung CY - Online meeting DA - 14.09.2020 KW - Hochfester Feinkornbaustahl KW - MAG-Schweißen KW - Kaltriss KW - TEKKEN PY - 2020 AN - OPUS4-51258 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Blasón Gonzalez, Sergio T1 - Determination of the fatigue limit and initial crack length by means of fracture mechanics N2 - The fatigue design of metallic components is usually based on two different approaches, namely total life and damage tolerance. The former takes into account both the initiation and propagation stages. The latter is based on fracture mechanics and needs an initial defect, which propagates until the critical size under cyclic loading, provided it is large enough. In this case, a residual life rather than a total life is obtained. The overall lifetime of a cyclically loaded structure involves four consecutive stages: a) crack initiation; b) propagation of microstructurally short cracks; c) propagation of physically/mechanically short cracks; d) propagation of long cracks. Considering the propagation from the short crack regime, the damage tolerance approach can be extended to adequately calculate the total life of a component. The fatigue strength of metallic materials containing defects depends on the non-propagation condition of small cracks emanating from these defects. In this work, the presence of mechanically short cracks from the beginning of the component's life is considered. Consequently, the methodology of analysis must be able to treat adequately local ligament yielding effects typical for short cracks and must include the thorough description of the crack closure effect up to the long-crack regime. In the analysis based on long cracks, the linear-elastic condition is mostly satisfied which allows the use of the linear elastic parameter ΔK for describing the crack driving force. On the contrary, this assumption is not adequate for mechanically short cracks because the crack depth is in the order of the plastic zone. Instead, an elastic-plastic driving force should be considered. Furthermore, the gradual build-up of the plasticity-induced crack closure effect must be considered, which implies a transition from the intrinsic (effective) threshold value, ΔKth,eff, to the long-crack threshold, ΔKth,LC. The effective component is a material parameter which is dependent on the elastic properties and crystal lattice. The gradual build-up of crack-closure is described by ΔKth,op which is a function of the plastic properties, grain-size, environment conditions, load ratio and crack-depth. The crack closure can be characterized experimentally by the so-called cyclic R-curve. Some other crack closure effects, such as roughness or oxide-debris induced, might be incorporated as well. The knowledge of the cyclic R-curve can be useful to determine the largest non-propagating crack size at the material fatigue limit. This is realised by means of the so-called cyclic R-curve analysis: The tangent criterion between the driving force and the cyclic R-curve define the transition between crack arrest and propagation. In this regard, a0 is defined as that crack depth which will only grow into a non-propagating crack due to the development of crack closure. The procedure outlined briefly here has been successfully applied to the determination of the fatigue limits of steel weldments. Considering the stochastic distribution of the weld geometric parameters (namely, weld toe radius, the flank angle, and the excess weld metal) it is possible to perform a full probabilistic cyclic R-curve analysis and determine this way the statistical distribution of the initial crack size at the weld toe at the fatigue limit. T2 - Virtual Conference on Mechanical Fatigue CY - Online meeting DA - 09.09.2020 KW - Cyclic R-curve KW - Fracture Mechanics KW - Fatigue Strength KW - Short Crack Propagation PY - 2020 AN - OPUS4-51238 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Dixneit, Jonny A1 - Dilger, K. A1 - Nitschke-Pagel, T. A1 - Hensel, J. A1 - Eslami, H. T1 - Schwingfestigkeitsverbesserung hochfester Schweißverbindungen mit Hilfe neuartiger LTT-Zusatzwerkstoffe N2 - Die Verwendung von LTT-Zusatzwerkstoffen stellt einen alternativen Ansatz zu den sonst üblichen Verfahren der Schweißnahtnachbehandlung zur Schwingfestigkeitserhöhung geschweißter Stahlkonstruktionen dar. Der wesentliche Wirkmechanismus beruht auf der Beeinflussung des Eigenspannungszustands durch die niedrige Martensitstarttemperatur bereits während des Schweißens. Dadurch werden die Druckeigenspannungen aus der behinderten Volumenausdehnung infolge Phasenumwandlung voll wirksam. Weiter weist die Schweißnaht eine hohe Härte auf, die die Schwingrissbildung verzögern kann, allerdings auch zu einer niedrigen Kerbschlagarbeit führt. Im vorliegenden Forschungsvorhaben wurden grundlegende Untersuchungen zur schweißtechnischen Verarbeitung eines LTT-Zusatzwerkstoffes durchgeführt. Dies beinhaltet die Sicherstellung der Schweißbarkeit sowie die Charakterisierung der Verbindungseigenschaften. Untersuchungen zur Schweißeignung machten deutlich, dass ein sicherer Einsatz in dem für hochfeste Stähle zur Verfügung stehenden Arbeitsfenster möglich ist. Der verwendete LTT-Zusatz auf Cr-Ni-Basis lässt sich mit hoher Nahtgüte fügen. Auch die mechanischen Eigenschaften erlauben den Einsatz im Bereich hochfester Stähle mit einer Streckgrenze von 960 MPa. Entwicklungspotential gibt es hinsichtlich der Zähigkeit. Die in dieser Arbeit erreichten Kerbschlagwerte liegen deutlich unter denen kommerziell verfügbarer konventioneller Schweißgüter. Die Untersuchungen belegen, dass der Effekt der martensitischen Phasenumwandlung im gesamten Schweißgut zum Tragen kommt. Die angestrebten hohen Druckeigenspannungen finden sich vornehmlich im Schweißgutinnern. Im weiteren Vorgehen wurden Schwingfestigkeitsuntersuchungen an den Stählen S355J2 und S960Q unter Verwendung konventioneller Zusatzwerkstoffe im Vergleich zum LTT-Zusatz durchgeführt. Die verwendeten Konstruktionsdetails sind ein Stumpfstoß unter Variation der Schweißnahtausführung (DY-Naht und V-Naht), ein Kreuzstoß mit HV-Naht sowie ein Überlappstoß mit einseitig und beidseitig geschweißter Kehlnaht. Weitergehend wurde eine bauteilähnliche Probe (die Längssteife) untersucht, bei der der LTT-Zusatzwerkstoff als zusätzliche Schweißlage aufgebracht wurde. Neben der Schwingfestigkeit wurden die Schweißnähte hinsichtlich der Eigenspannungen, der Eigenspannungsstabilität im Schwingversuch sowie metallografisch charakterisiert. Eine generell positive Wirkung des LTT-Zusatzwerkstoffes im Hinblick auf die Schwingfestigkeitssteigerung kann nicht bestätigt werden. Teilweise ist eine Steigerung der Schwingfestigkeit bei Substitution konventioneller Zusatzwerkstoffe zu beobachten, teilweise zeigt sich kein Effekt. Ursächlich hierfür ist die bei manchen Stoßformen mangelnde Steifigkeit quer zur Schweißnaht, die zur Ausbildung hoher Druckeigenspannungen infolge Phasenumwandlung notwendig wäre. Die bauteilähnliche Längssteife bestätigt allerdings das grundlegende Potential der LTT-Zusatzwerkstoffe bei Vorliegen hinreichender Steifigkeit. KW - Schweißen KW - Eigenspannungen KW - Schwingfestigkeit KW - Hochfester Stahl KW - LTT PY - 2020 UR - https://matplus.shop/produkt/p-1060-schwingfestigkeitsverbesserung-hochfester-schweissverbindungen-mit-hilfe-neuartiger-ltt-zusatzwerkstoffe SN - 978-3-946885-75-7 VL - P 1060 SP - 1 EP - 123 PB - Verlag und Vertriebsgesellschaft CY - Düsseldorf AN - OPUS4-51216 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Taparli, Ugur Alp T1 - Online weld analysis by laser-induced breakdown spectroscopy (LIBS) N2 - Principles of online weld inspection using laser-induced breakdown spectroscopy, inspection of stationary and bead-on-plate welds containing solidification cracks. T2 - Symposium on Materials and Joining Technology CY - Online meeting DA - 07.09.2020 KW - Welding KW - LIBS KW - Austenitic stainless steel KW - Metal vapor KW - Hot cracking PY - 2020 AN - OPUS4-51191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - Martensitumwandlung in situ analysiert mit Röntgenstrahlung N2 - Die dehnungsinduzierte Martensitbildung wurde mittels Röntgen-Diffraktion und -Radiographie mit dem EDDI-Instrument am BESSY II in supermartensitischem Stahl mit Anlassaustenit untersucht. Die Bildung wird durch Wasserstoff im Gefüge unterdrückt. Die Duktilität von wasserstofffreiem SMSS korreliert mit dem Anteil an dehnungs-induziertem Martensit T2 - Symposium on Materials and Joining Technology CY - Online meeting DA - 07.09.2020 KW - Wasserstoff KW - Materialschädigung KW - Materialschaedigung KW - Synchrotron PY - 2020 AN - OPUS4-51190 LA - deu 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 DO - 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 - Serrano-Munoz, Itziar A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Sprengel, Maximilian A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Nolze, Gert A1 - Saliwan Neumann, Romeo A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - The residual stress in as‑built Laser Powder Bed Fusion IN718 alloy as a consequence of the scanning strategy induced microstructure N2 - The effect of two types of scanning strategies on the grain structure and build-up of Residual Stress (RS) has been investigated in an as-built IN718 alloy produced by Laser Powder Bed Fusion (LPBF). The RS state has been investigated by X-ray diffraction techniques. The microstructural characterization was performed principally by Electron Backscatter Diffraction (EBSD), where the application of a post-measurement refinement technique enables small misorientations (< 2°) to be resolved. Kernel average misorientation (KAM) distributions indicate that preferably oriented columnar grains contain higher levels of misorientation, when compared to elongated grains with lower texture. The KAM distributions combined with X-ray diffraction stress maps infer that the increased misorientation is induced via plastic deformation driven by the thermal stresses, acting to self-relieve stress. The possibility of obtaining lower RS states in the build direction as a consequence of the influence of the microstructure should be considered when envisaging scanning strategies aimed at the mitigation of RS. KW - Additive manufacturing KW - LPBF KW - Residual stress KW - Inconel 718 KW - Kernel average misorientation KW - Texture PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511769 DO - https://doi.org/10.1038/s41598-020-71112-9 VL - 10 IS - 1 SP - 14645 AN - OPUS4-51176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Charmi, Amir A1 - Falkenberg, Rainer A1 - Ávila Calderón, 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 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511719 DO - https://doi.org/10.1016/j.msea.2020.140154 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 - Taparli, Ugur Alp A1 - Kannengießer, Thomas A1 - Griesche, Axel T1 - Tungsten inert gas bead-on-plate weld chemical composition analysis by laser-induced breakdown spectroscopy N2 - Chemical compositions of a weld can be varying locally as a result of the welding process. These local variations can be due to the vaporization of individual alloying elements. In this work, tungsten inert gas (TIG) bead-on-plate stainless steel welds of EN grade 1.4404 and 1.4435 were investigated using laser-induced breakdown spectroscopy (LIBS) on the completed welds. This study aims to reveal the welding parameters’ influence on the resulting local chemical compositions of the stainless steel welds. We demonstrated Mn vaporize before Cr due to its lower latent enthalpy of vaporization. Hence, Mn accumulates on the heat-affected zone (HAZ) both sides across the weld bead by being swept away through the circulation flow of the welding plasma. Additionally, increasing the heat input tends to enhance the accumulated Mn content on the HAZ as well as increasing the shielding gas flow rate. The results are in good agreement with the literature and proved that LIBS is an effective method to inspect completed welds. T2 - Symposium on Materials and Joining Technology CY - Magdeburg, Germany DA - 07.09.2020 KW - LIBS TIG welding KW - Austenitic stainless steels KW - Chemical composition KW - In situ measurement PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511595 DO - https://doi.org/10.1088/1757-899X/882/1/012023 SN - 1757-8981 SN - 1757-899X VL - 882 IS - 012023 SP - 1 EP - 8 PB - IOP Publishing CY - Bristol AN - OPUS4-51159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schaupp, Thomas T1 - Modified TEKKEN test for studying hydrogen-assisted cracking in high-strength structural steels N2 - In the present work, the complex interactions of the influences of material, welding process and seam configuration and the restraint of shrinkage on the residual stresses and the influence of diffusible hydrogen on hydrogen-assisted cracking (HAC) in the high-strength steel S960QL were investigated. For this purpose, self-restraint specimens were selected using the TEKKEN test with correspondingly adapted seam opening angles and a restraint intensity of approx. RFy = 17 kN/(mm·mm). The variation of the seam opening angle of the test seams was between 30° and 60°. Due to the comparatively high restraint of shrinkage in the transverse direction of the weld, high tensile residual stresses in the weld metal were expected for both weld seam configurations. In addition, a dehydrogenation heat treatment (DHT) for HAC prevention under restraint of shrinkage was verified. In order to keep distortion and heat input as low as possible, the seam geometries were manufactured from the solid material by means of electric discharge machining (EDM). Both, solid wire and metal cored wire were used. In addition, hydrogen was added to the shielding gas in solid wire welding to increase diffusible hydrogen concentration. Moreover, welding residual stresses at the weld seam surface, which were measured by using mobile X-ray diffraction, were taken into account to evaluate the HAC behavior. DHT was carried out at 250 °C for 4 h in an external furnace. T2 - 73rd IIW Annual Assembly: Commission II-A CY - Online meeting DA - 15.07.2020 KW - High-strength steel KW - Gas metal arc welding KW - Hydrogen-assisted cracking KW - TEKKEN test KW - Residual stresses KW - Dehydrogenation heat treatment PY - 2020 AN - OPUS4-51035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Ernst, W. A1 - Spindler, H. A1 - Kannengießer, Thomas T1 - Hydrogen-assisted cracking of GMA welded 960 MPa grade high-strength steels N2 - High-strength steels with yield strength of 960 MPa are susceptible to hydrogen-assisted cracking (HAC) during welding processing. In the present paper, the implant test is used to study HAC in a quenched and tempered steel S960QL and a high-strength steel produced by thermo-mechanical controlled process S960MC. Welding is performed using the gas metal arc welding process. Furthermore, diffusible hydrogen concentration (HD) in arc weld metal is determined. Based on the implant test results, lower critical stress (LCS) for complete fracture, critical implant stress for crack initiation, and embrittlement index (EI) are determined. At HD of 1.66 ml/100 g, LCS is 605 MPa and 817 MPa for S960QL and S960MC, respectively. EI is 0.30 and 0.46 for S960QL and S960MC, respectively. Fracture surfaces of S960QL show higher degradation with reduced deformation. Both, higher EI of S960MC and fractography show better resistance to HAC in the HAZ of S960MC compared to S960QL. KW - High-strength steel KW - Welding KW - Diffusible hydrogen KW - Hydrogen-assisted cracking KW - Heat-affected zone KW - Implant test PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-510307 DO - https://doi.org/10.1016/j.ijhydene.2020.05.077 SN - 0360-3199 VL - 45 IS - 38 SP - 20080 EP - 20093 PB - Elsevier Ltd CY - Amsterdam, NL AN - OPUS4-51030 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Werner, Tiago T1 - Damage tolerant design of metallic AM parts N2 - Additive Manufacturing (AM) opens new possibilities in the design of metallic components, including very complex geometries (e.g. structures optimized for certain loads), optimization of materials (e.g. gradient materials) and cost-effective manufacturing of spare parts. In the recent years, it has been used for the first safety-relevant parts, but the consideration of cyclic mechanical behavior in AM is still at the very beginning. The reason for this is the complexity of mechanical material properties, i.e. inhomogeneity, anisotropy and a large number of defects frequently textured and characterized by large scattering in size. Additionally, high surface roughness and residual stresses with complex distributions are typical of AM. Due to these reasons, the transferability of experimentally determined properties from specimens to components is a challenge. This presentation provides an overview of the questions concerning the application of AM to safety-relevant components. Possible strategies for the fatigue design of such components are presented. Besides the Kitagawa-Takahashi-diagram method and the cyclic R-curve analysis as approaches for damage-tolerant design, the identification of critical locations, the problem of representative material properties and the handling of residual stresses are addressed. T2 - 4th international symposium on Fatigue Design and Material Defects CY - Online meeting DA - 26.05.2020 KW - Additive Manufacturing KW - Cyclic R-Curve KW - Component assessment PY - 2020 AN - OPUS4-50938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vollert, F. A1 - Thomas, Maximilian A1 - Kromm, Arne A1 - Gibmeier, J. T1 - Solidification Cracking Assessment of LTT Filler Materials by Means of Varestraint Testing and μCT N2 - Investigations of the weldability of metals often deal with hot cracking, as one of the most dreaded imperfections during weld fabrication. The hot cracking investigations presented in this paper were carried out as part of a study on the development of low transformation temperature (LTT) weld filler materials. These alloys allow to mitigate tensile residual stresses that usually arise during welding using conventional weld filler materials. By this means, higher fatigue strength and higher lifetimes of the weld can be achieved. However, LTT weld filler materials are for example, high-alloyed Cr/Ni steels that are susceptible to the formation of hot cracks. To assess hot cracking, we applied the standardized modified varestraint transvarestraint hot cracking test (MVT), which is well appropriate to evaluate different base or filler materials with regard to their hot cracking susceptibility. In order to consider the complete material volume for the assessment of hot cracking, we additionally applied microfocus X-ray computer tomography (μCT). It is shown that by a suitable selection of welding and MVT parameter the analysis of the complete 3D hot crack network can provide additional information with regard to the hot cracking model following Prokhorov. It is now possible to determine easy accessible substitute values (e.g., maximum crack depth) for the extent of the Brittleness Temperature Range (BTR) and the minimum critical strain Pmin. KW - LTT weld filler materials KW - μCT-analysis KW - Hot cracking KW - Varestraint test PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509126 DO - https://doi.org/10.3390/ma13122726 VL - 13 IS - 12 SP - 2726 PB - MDPI AN - OPUS4-50912 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Spranger, Felix A1 - Schirdewahn, S. A1 - Kromm, Arne A1 - Merklein, M. A1 - Hilgenberg, Kai T1 - On the influence of TiB2, TiC, and TiN hard particles on the microstructure of localized laser dispersed AISI D2 tool steel surfaces N2 - The control of friction and wear is a major concern in many industrial applications. A promising method for tailored surface modification is the so-called laser implantation technique. This method combines surface texturing and material optimization in one processing step by a localized dispersing of hard ceramic particles using pulsed laser radiation. Wear resistant, protruding micrometric features (implants) with defined geometry can be created in a deterministic pattern where needed on highly stressed surfaces, i.e., on forming or cutting tools. However, in order to maintain the implants over the tool’s lifetime, a suitable selection of hard ceramic particles is a prerequisite. They must provide a defect-free metal matrix composite with a high share of homogeneously distributed particles and, especially, high implant hardness. In this study, TiN, TiC, and TiB2 hard particles were compared as implant materials for the first time. By a systematic variation of pulse power and pulse duration, their dispersing behavior and influence on the material properties of AISI D2 tool steel were investigated. Although all powder materials had grain sizes smaller than 10 μm, it was possible to disperse them by pulsed laser radiation and to obtain defect-free protruding implants. The highest share of dispersed particles (∼64%) was observed for TiB2. By scanning electron microscopy and energy dispersive x-ray spectroscopy, it was also shown that a significant share of the preplaced particles was dissolved by the laser beam and precipitated as nanometer sized particles within the matrix during solidification. These in situ formed particles have a decisive influence on the material properties. While the TiN and TiC implants have shown maximum hardness values of 750 and 850 HV1, the TiB2 implants have shown the highest hardness values with more than 1600 HV1. By x-ray diffraction, it was possible to ascribe the lower hardness values of TiC and TiN implants to high amounts of retained austenite in the metal matrix. By implanting TiB2, the formation of retained austenite was successfully suppressed due to the in situ formation of TiC particles, which was proven by electron backscatter diffraction. In conclusion, all the implant materials are basically suitable for laser implantation on AISI D2 tool steel. However, TiB2 has shown the most promising results. T2 - ICALEO 2019 CY - Orlando, FL, USA DA - 07.10.2019 KW - Laser implantation KW - Surface texturing KW - AISI D2 KW - TiB2 KW - TiN KW - TiC KW - Retained Austenite KW - Localized laser dispersing PY - 2020 DO - https://doi.org/10.2351/7.0000059 VL - 32 IS - 2 SP - 022028 EP - 022028-9 PB - AIP Publishing AN - OPUS4-50712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Hannemann, Andreas A1 - Schultz, Michael A1 - Griesche, Axel T1 - On the Genesis of Artifacts in Neutron Transmission Imaging of Hydrogenous Steel Specimens N2 - Hydrogen-charged supermartensitic steel samples were used to systematically investigate imaging artifacts in neutron radiography. Cadmium stencils were placed around the samples to shield the scintillator from excessive neutron radiation and to investigate the influence of the backlight effect. The contribution of scattered neutrons to the total detected intensity was investigated by additionally varying the sample-detector distance and applying a functional correlation between distance and intensity. Furthermore, the influence of the surface roughness on the edge effect due to refraction was investigated. KW - Refraction KW - Neutron imaging KW - Hydrogen KW - Supermartensitic steel KW - Backlight KW - Scattering PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506587 DO - https://doi.org/10.3390/jimaging6040022 VL - 6 IS - 22 SP - 1 EP - 10 PB - MDPI CY - Basel, Switzerland AN - OPUS4-50658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schröpfer, Dirk A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Influence of welding stresses on relief cracking during heat treatment of a creep-resistant 13CrMoV steel: Part II - Mechanisms of stress relief cracking during post weld heat treatment N2 - Welding of 13CrMoV9-10 vanadium steel requires care due to an increased susceptibility to stress relief cracking during post weld heat treatment. Previous research into the crack formation in creep-resistant steels has focused on thermal and metallurgical factors; however, little knowledge has been gathered regarding the crack formation during post weld heat treatment considering real-life restraint conditions. This work is subdivided in two parts. Part I showed that an increasing heat input during submerged arc welding under restraint led to an increasing stress level in the joint prior to the post weld heat treatment. The magnitude of stress relief cracking observed in the heat-affected zone after the post weld heat treatment is affected by the heat input. In Part II of this work, the cracks and the associated microstructure which occurred under restraint were studied. The application of a Special acoustic emission analysis indicated that the cracks formed in a temperature range between 300 and 500 °C during the post weld heat treatment. The toughness in the heat-affected zone of the restrained welds was affected by the welding heat input. Microstructural analyses of all specimens revealed accelerated aging due to precipitation of carbides during post weld heat treatment under restraint. KW - Welding KW - Creep-resistant steel KW - Post weld heat treatment KW - Stress relief cracking PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506283 DO - https://doi.org/10.1007/s40194-020-00881-8 SN - 1878-6669 VL - 64 SP - 819 EP - 829 PB - Springer CY - Berlin AN - OPUS4-50628 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schröpfer, Dirk A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Influence of welding stresses on relief cracking during heat treatment of a creep-resistant 13CrMoV steel: Part I - Effect of heat control on welding stresses and stress relief cracking N2 - The avoidance of failures during the fabrication or operation of petrochemical reactors made of creep-resistant, low-alloy steels as 13CrMoV9-10 requires still research despite over 60 years of international investigations in the field of stress relief cracking. The quality of modern base materials and filler metals leads to the fact that previously known crack causes, such as impurities of S or P, recede into the background. Rather, the causes are increasingly to be found in the fabrication process. Investigations on the influence of heat control on the stresses in welded components and thus on the stress relief cracking sensitivity under realistic manufacturing conditions are not yet available. This work is subdivided in two parts. Part 1 of this study focused on the effect of heat control during submerged arc welding on the stresses. For this purpose, a testing facility was applied, which allows to observe the forces and moments accumulating during welding or heat treatment in a component-like specimen under shrinkage restraint. The stress acting in the specimen increases with higher preheat/interpass temperatures and higher heat input. During the heat treatment, the stresses are relieved. Nevertheless, cracks are formed already during heating. The total crack length correlates with the heat input. KW - Welding KW - Creep-resistant steel KW - Post weld heat treatment KW - Stress relief cracking PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506271 DO - https://doi.org/10.1007/s40194-020-00875-6 SN - 1878-6669 VL - 64 IS - 5 SP - 807 EP - 817 PB - Springer CY - Berlin AN - OPUS4-50627 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thomas, Maximilian A1 - Vollert, F. A1 - Weidemann, Jens A1 - Gibmeier, J. A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals N2 - The subject of this study is how, and to what extent, Varestraint/Transvarestraint test results are influenced by both testing parameters and characteristics of evaluation methods. Several different high-alloyed martensitic LTT (low Transformation temperature) filler materials, CrNi and CrMn type, were selected for examination due to their rather distinctive solidification cracking behaviour, which aroused interest after previous studies. First, the effects of different process parameter sets on the solidification cracking response were measured using standard approaches. Subsequently, microfocus X-ray computer tomography (μCT) scans were performed on the specimens. The results consistently show sub-surface cracking to significant yet varying extents. Different primary solidification types were found using wavelength dispersive X-ray (WDX) analysis conducted on filler metals with varying Cr/Ni equivalent ratios. This aspect is regarded as the main difference between the CrNiand CrMn-type materials in matters of cracking characteristics. Results show that when it comes to testing of modern highperformance alloys, one set of standard Varestraint testing parameters might not be equally suitable for all materials. Also, to properly accommodate different solidification types, sub-surface cracking has to be taken into account. KW - Solidification cracking KW - Varestraint testing KW - MVT KW - LTT filler metal KW - Microfocus X-ray computer tomography (μCT) PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506039 DO - https://doi.org/10.1007/s40194-020-00895-2 VL - 64 SP - 913 EP - 923 PB - Springer Nature CY - Heidelberg, New York AN - OPUS4-50603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Taparli, Ugur Alp A1 - Kannengießer, Thomas A1 - Cieslik, K. A1 - Mory, D. A1 - Griesche, Axel T1 - In situ chemical composition analysis of a tungsten-inert-gas austenitic stainless steel weld measured by laser-induced breakdown spectroscopy N2 - The chemical composition of a weld metal determines the resulting solidification mode of stainless steel and the consequent weld metal quality. In this work tungsten inert gas (TIG) welding of EN grade 1.4435 austenitic stainless steel was monitored using laser-induced breakdown spectroscopy (LIBS) for the in situ measurement of chemical composition changes. This research aims to prototype a real-time chemical composition analysis system for welding applications and prove the feasibility of such quality control loop. LIBS was used to investigate in situ the monitoring of metal vaporization during TIG welding. We found Mn vapor formation above the weld pool and subsequent condensation of Mn on the weld metal surface using LIBS. Post-weld line scans were conducted by LIBS on various welds produced with different welding currents. Local changes of Ni and Mn were observed at higher welding currents. The results are in good agreement with the literature and proved that LIBS can be used in situ to inspect the TIG welding process. T2 - 10th Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy CY - Brünn, Czechia DA - 08.09.2019 KW - LIBS KW - Welding KW - Austenitic stainless steel KW - Metal vapor KW - In situ measurement PY - 2020 DO - https://doi.org/10.1016/j.sab.2020.105826 SN - 0584-8547 VL - 167 SP - 105826 PB - Elsevier B.V. CY - Amsterdam, Niederlande AN - OPUS4-50582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel T1 - Measurement of Hydrogen Distributions in Metals by Neutron Radiography and Tomography N2 - Neutron imaging is a valuable tool for measuring hydrogen distributions qualitatively and quantitatively in metals. Time-resolved neutron radiography allows to measure hydrogen mass flow inside cm thick steel samples with ~10 s temporal resolution. Hydrogen accumulations around cracks in embrittled iron samples can be visualized three-dimensionally by neutron tomography. This quality of information allows new insights for the analysis of damage mechanisms on a micrometer scale, e.g. of hydrogen blistering. Even the gas pressure of molecular hydrogen in crack cavities has been measured from tomographic reconstructions to be in the range of 5 MPa to 15 MPa for technical iron. Further, this method is non-destructive and provides local information in situ and in all three dimensions with a spatial resolution of 20 - 30 µm. The combination with other methods gives a new quality of information, e.g. of the hydrogen allocation on fractured surfaces. T2 - Symposium on large scale facilities CY - Berlin, Germany DA - 09.03.2020 KW - Hydrogen embrittlement KW - Neutron imaging KW - Hydrogen diffusion KW - Neutron radiography KW - Neutron tomography PY - 2020 AN - OPUS4-50548 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schaupp, Thomas T1 - Zur Bewertung der Kaltrissempfindlichkeit moderner hochfester Feinkornbaustähle mit dem Implant-Test N2 - Der Implant-Test nach ISO 17642-3 gehört zur Gruppe der fremdbeanspruchten Kaltrisstests, bei dem eine äußere Beanspruchung auf einen zylindrischen Stab (Implant-Probe) definiert aufgebracht wird. Mit dieser Kaltrissprüfung wurden vergleichende Analysen zur Kaltrissempfindlichkeit der modernen hochfesten Feinkornbaustähle S960MC und S960QL durchgeführt. Zudem kamen sowohl Massiv- als auch Metallpulverfülldraht zur Variation der Wasserstoffkonzentration zum Einsatz. Der Einsatz des modernen modifizierten Sprühlichtbogens ermöglichte außerdem die Untersuchung des Einbrandprofils auf die Kaltrissbildung. T2 - Sitzung des NA 092-00-05 GA „Gemeinschaftsarbeitsausschuss NAS/NMP: Zerstörende Prüfung von Schweißverbindungen (DVS AG Q 4/Q 4.1)“ CY - Hamm, Germany DA - 04.03.2020 KW - Hochfester Feinkornbaustahl KW - MAG-Schweißen KW - Wasserstoff KW - Kaltriss KW - Implant-Test PY - 2020 AN - OPUS4-50506 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vollert, F. A1 - Thomas, Maximilian A1 - Kromm, Arne A1 - Gibmeier, J. T1 - Hot crack assessment of LTT welds using μCT N2 - Investigations on weldability often deal with hot cracking, as one of the most popular failure during weld fabrication. The modified varestraint transvarestraint hot cracking test (MVT) is well known for the assessment of the hot cracking susceptibility of materials. The shortcoming of this approach is that the information is only from the very near surface region, which inhibits access to the characteristic of the hot crack network in the bulk. Here, we report about a new approach, illustrated in the example of low transformation temperature (LTT) weld filler materials, to monitor the entire 3D hot crack network after welding by means of microfocus X-ray computer tomography (μCT). T2 - 10th Conference on Industrial Computed Tomography (iCT 2020) CY - Wels, Austria DA - 04.02.2020 KW - Varestraint testing KW - LTT weld filler materials KW - Hot cracking KW - Welding KW - μCT-analysis PY - 2020 DO - https://doi.org/https://doi.org/10.58286/25121 SN - 1435-4934 VL - 25 IS - 2 SP - 1 EP - 7 PB - NDT.net CY - Kirchwald AN - OPUS4-50341 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe T1 - Application of fracture mechanics to welds with crack origin at the weld toe—a review. Part 2: welding residual stresses. Residual and total life assessment N2 - The two-part paper series provides an overview on the state-of-the-art in the application of engineering fracture mechanics to weldments limited to butt and fillet welds with crack initiation at weld toes. In the present second part, one focus is on welding residual stresses, their characteristics and stability under cyclic loading and their effect on structural integrity. Subsequently, features will be addressed which are essential for applying fracture mechanics to overall fatigue life and fatigue strength considerations of weldments. These comprise fatigue life relevant initial crack sizes and multiple crack initiation and Propagation due to various stress peaks along the weld toe. A concept is briefly introduced which covers all these aspects. KW - Fracture mechanics KW - Welding residual stresses KW - Multiple crack propagation KW - Fatigue strength PY - 2020 DO - https://doi.org/10.1007/s40194-019-00816-y VL - 64 IS - 1 SP - 151 EP - 169 PB - Springer AN - OPUS4-50263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -