TY - CONF A1 - Gibmeier, J. A1 - Weidemann, Jens A1 - Dixneit, Jonny A1 - Kannengießer, Thomas A1 - Kromm, Arne T1 - Influence of structural stiffness on the residual stresses during welding of low transformation temperature alloys N2 - Low Transformation Temperature (LTT) alloys are high alloyed filler materials, which exhibit a martensitic phase transformation at comparatively low temperatures in order to prevent high tensile residual stresses. A number of publications have already shown that even compressive residual stresses can be observed when using LTT filler materials. Up to know it is not clear in which way this it applicable to multi-run welding exhibiting high shrinkage restraint and complex heat input. In this study the potential for stress reduction during welding of LTT alloys was studied by numerical simulation. This allows for evaluation of the stress development in every single weid run. Additionally, the impact of the structural stiffness was incorporated by modelling a special sample geometry exhibiting a high intensity of restraint. The results show that the stress formation in weid longitudinal direction is determined by the phase transformation as high compressive residual stresses were found here independent from the weid run. On the other hand the transformation induced stresses in weid transverse direction are superimposed by tensile stresses originated from shrinkage restraint. With increasing number of runs the tensile residual stress level is raised. The results were confirmed by residual stress measurements using diffraction methods. T2 - 11th International Seminar - Numerical Analysis of Weldability CY - Graz, Austria DA - 27.09.2015 KW - Influence KW - Structural stiffness KW - Residual stresses KW - Low transformation KW - Temperature alloys KW - Welding PY - 2016 SN - 978-3-85125-490-7 SN - 2410-0544 SP - 259 EP - 276 PB - Verlag der Technischen Universität Graz CY - Graz AN - OPUS4-38998 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Optimization of welding loads using modified spray arc process N2 - Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern steel constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and the welding process become more challenging with increasing material strength due to higher elastic ratios. The formation of high residual stresses, which are able to diminish lifetime, load capacity and component safety, has to be avoided. Recent numerical and experimental analyses have shown a strong influence of the heat control and the rigidity of the weld on the welding stresses. Global reaction stresses due to an external shrinkage restraint superimpose with local residual stresses in the weld seam. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by the power source manufactures with almost equal characteristics. They provide several well-known technical and economic benefits, like the possibility of welding narrower seam configurations. As a result a smaller weld volume, total heat input and, therefore, reduced welding stresses are achievable. This research focuses on the welding loads due to modified weld seams. The global reaction forces in welded components due to an external shrinkage restraint were investigated in a special in-house developed testing facility. Additionally, the superposition of the local residual stresses, global stresses and bending moments were analysed with the help of X-ray diffraction. The intensity of the restraint, the weld seam configuration and the weld process (transitional arc and modified spray arc) were varied for a statistical evaluation of the resulting welding loads. It was observed that under restraint a smaller weld seam volume affects reduced reaction stresses. T2 - IIW Intermediate Meeting, C-IIA CY - Madrid, Spain DA - 29.02.2016 KW - Process parameters KW - Residual stresses KW - MAG Welding KW - Restraint KW - High-strength steels PY - 2016 AN - OPUS4-38785 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Optimization of welding loads using modified spray arc process N2 - Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern steel constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and the welding process become more challenging with increasing material strength due to higher elastic ratios. The formation of high residual stresses, which are able to diminish lifetime, load capacity and component safety, has to be avoided. Recent numerical and experimental analyses have shown a strong influence of the heat control and the rigidity of the weld on the welding stresses. Global reaction stresses due to an external shrinkage restraint superimpose with local residual stresses in the weld seam. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by the power source manufactures with almost equal characteristics. They provide several well-known technical and economic benefits, like the possibility of welding narrower seam configurations. As a result a smaller weld volume, total heat input and, therefore, reduced welding stresses are achievable. This research focuses on the welding loads due to modified weld seams. The global reaction forces in welded components due to an external shrinkage restraint were investigated in a special in-house developed testing facility. Additionally, the superposition of the local residual stresses, global stresses and bending moments were analysed with the help of X-ray diffraction. The intensity of the restraint, the weld seam configuration and the weld process (transitional arc and modified spray arc) were varied for a statistical evaluation of the resulting welding loads. It was observed that under restraint a smaller weld seam volume affects reduced reaction stresses. T2 - IIW Annual Assembly 2016 CY - Melbourne, Australia DA - 10.07.2016 KW - Process parameters KW - Residual stresses KW - MAG Welding KW - Restraint KW - High-strength steels PY - 2016 AN - OPUS4-38787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pasternak, H. T1 - Residual stresses and imperfections in welded high-strength I-shape sections N2 - This article addresses the imperfections in high-strength steel I-shape sections caused by weld assembly. Load influencing imperfections are assumed mainly as deviations from the ideal shape (e.g. bending distortion) and longitudinal residual stresses. The quality of a numerically aided design of components exposed to either compression and/or bending is significantly dependent on those parameters. In this scope, major gaps in knowledge are still present. Eurocode (EC) is providing robust simplified models that date back to the 1960's and 70's. As a result, the ultimate limit state (ULS) is approached on a quite conservative basis. The investigations are presented in this article are aimed to give further guidance on these values in component-like specimens in the context of Eurocode. T2 - 6th Conference on Structural Engineering, Mechanics and Computation CY - Cape Town, South Africa DA - 05.09.2016 KW - Residual stresses KW - Weld imperfections KW - I-shape sections KW - High-strength steel KW - Numerical modeling PY - 2016 AN - OPUS4-37635 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Launert, B. T1 - Welding residual stresses in high-strength steels: experimental results N2 - Welded plate girders are used in heavy steel construction, industrial buildings and bride construction. Residual stresses are present in all plate structures. They are mainly caused by welding. In addition, they influence the load bearing capacity of these welded components. However, Eurocode (EC) does not provide any specific residual stress patterns for consideration of residual stress impact on load capacity. Hence, the decision for a particular problem has to be made by the designer. Many codes, including EC 3, permit the use of non-linear finite element analysis (FEA) for the design of structures. For that purpose, the contribution gives an overview on recent results derived from welded I-girders made from mild steel S355 and high-strength steel S690QL. Weld residual stresses have been investigated by X-ray diffraction (XRD) on small-scale specimen. In addition, residual stresses of welded component-like I-girders have been studied using the sectioning technique. The results confirmed the beneficial effect of certain edge preparation of the plates by flame cutting prior to welding. High-strength steels like the S690 can contribute to both: increased load capacity and decreased influence of weld residual stresses. T2 - International Colloquium on Stability and Ductility of Steel Structures CY - Timisoara, Romania DA - 30.05.2016 KW - Welding KW - Residual stresses KW - High-strength steel KW - Experimental results PY - 2016 AN - OPUS4-37031 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pasternak, H. T1 - Advanced residual stress assessment of plate girders by welding simulation: An overview N2 - Welded plate girders are used in heavy steel construction, industrial buildings and bride construction. Residual stresses are present in all plate structures. They are mainly caused by welding. In addition, they influence the load bearing capacity of these welded components. However, Eurocode (EC) does not provide any specific residual stress patterns for consideration of residual stress impact on load capacity. Hence, the decision for a particular problem has to be made by the designer. Many codes, including EC 3, permit the use of non-linear finite element analysis (FEA) for the design of structures. This contribution gives an overview on recent research topics: modeling, experimental measuring and evaluation of residual stresses as well as welding simulation tools and simplified methodologies for assessment of weld residual stresses. T2 - Modern Building Material, Structures and Techniques - MBMST 2016 CY - Vilnius, Lithuania DA - 26.05.2016 KW - Residual stresses KW - Welding KW - Measurement KW - Numerical modeling KW - Component PY - 2016 AN - OPUS4-37028 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Launert, B. T1 - Residual stress influence on the flexural buckling of welded I-girders N2 - Welded plate girders are used in heavy steel construction, industrial buildings and bride construction. Residual stresses are present in all plate structures. They are mainly caused by welding. In addiiton, they influence the load bearing capacity of these welded components. However, Eurocode (EC) does not provide any specific residual stress patterns for consideration of residual stress impact on load capacity. Hence, the decision for a particular problem has to be made by the designer. Many codes, including EC 3, permit the use of non-linear finite element analysis (FEA) for the design of structures. Recent developments in the last years, enabled the use of computerized models instead of laboratory experiments. In this scope, the FE-model should include all relevant factors properly. This important if considering that weld residual stresses can be a critical assessment factor. In addition, measuring of residual stresses is difficult, time consuming and expensive, it is therefore common to use founded distribution functions (e.g. Swedish BSK 99). Welding simulation tools offer new possibilities for a realistic assessment of weld-induced stresses and deformations. However, the modeling and the computational effort for large structural components is still not in a practicable range and a simplified methodology is in needed. As a result, a new approach (suitable for capacity analysis) is presented and detailed in the present contribution. T2 - 10th International Conference on Residual Stresses CY - Sydney, Australia DA - 03.07.2016 KW - Welding KW - Residual stresses KW - Load capacity KW - Numerical modeling KW - Component PY - 2016 AN - OPUS4-37027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Klingbeil, Dietmar A1 - Svendsen, B. A1 - Reusch, F. T1 - Gurson-based modelling of ductile damage and failure during cyclic loading processes at large deformation N2 - Purpose is the formulation, numerical implementation, identification and application of a material model for ductile damage and failure during cyclic and non-proportional loading. The authors combined a hyperelasticity-based elasto-plastic model for non-linear isotropic as well as kinematic hardening with a modified Gurson model. Evolution strategy helped identify the model parameters for the high-strength steel 10MnMoNi5-5. The simulation of ductile failure in fracture mechanics specimens verified the model with respect to cyclic loading at two temperatures. The simulation of additional fracture mechanics applications validated the model as to the development of residual stresses at the crack tip under cyclic loads. KW - Ductile damage KW - Combined non-linear hardening with cyclic loading KW - Finite-element simulation KW - Material parameter identification KW - Residual stresses PY - 2016 UR - http://www.sciencedirect.com/science/article/pii/S0013794416301138 DO - https://doi.org/10.1016/j.engfracmech.2016.03.023 SN - 0013-7944 VL - 160 SP - 95 EP - 123 PB - Pergamon-Elsevier Science Ltd. CY - Oxford, UK AN - OPUS4-36121 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -