TY - JOUR A1 - Dixneit, Jonny A1 - Kromm, Arne A1 - Hannemann, Andreas A1 - Friedersdorf, Peter A1 - Kannengießer, Thomas A1 - Gibmeier, J. T1 - In-situ load analysis in multi-run welding using LTT filler materials N2 - Modifying the level of mostly detrimental welding residual stresses already during the welding process would be highly attractive as time- and cost-consuming post processing may be prevented. The nature of stress buildup during welding-associated cooling is highly affected by phase transformations. Up to now, it is not clear in which way this is applicable to real component welding exhibiting high shrinkage restraint and complex heat input. In this study, two different low transformation temperature (LTT) alloys have been investigated concerning the stress development in restrained multi-run butt welding in order to evaluate the potential of stress reduction. Pulsed gas metal arc welding (P-GMAW) welding was executed on a testing facility designed to simulate real lifelike restraint conditions of component weldments. The effect of reducedMS-temperatures and the heat control on the globally acting stresses was monitored by in-situ measurement of the reaction forces during welding fabrication. Additional local residual stress measurements allowed analyzing global as well as local loading of the welded construction. Although phase transformation has a significant influence on unloading the joint during each weld pass, the reaction stress upon cooling to room temperature seems to be determined mainly by the heat input. On the surface, low longitudinal residual stresses were observed in case of LTT whereas transverse residual stresses are less affected. T2 - 69th IIW Annual Assembly and International Conference CY - Melbourne, Australia DA - 10.07.2016 KW - Phase transformation temperature KW - Residual stress KW - Welding KW - Dilution KW - Restraint PY - 2016 U6 - https://doi.org/10.1007/s40194-016-0373-1 SN - 0043-2288 VL - 60 IS - 6 SP - 1159 EP - 1168 PB - Springer CY - Heidelberg AN - OPUS4-37892 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Engineering approach to assess residual stresses in welded components N2 - Present trends to lightweight design lead to an expanding relevance of high-strength fine-grained structural steels especially in mobile crane constructions. With growing material strength, the challenge for welding fabrication increases, since high loading capacities and safety requirements have to be accomplished. The utilisation of the high strength potential often requires complex constructions associated with high restraint conditions while welding. Increased residual stresses may occur due to superimposing reaction and restraint stresses, which have to be quantified and evaluated to ensure the safety and integrity of high-strength steel constructions. Particularly, the scope of residual stresses has to be taken into account for different effects in the HAZ, notches, weld and base metal. Commonly, conservative assumptions of residual stresses lead to distinct underestimations of the load bearing capacity particularly for welded high-strength steel constructions. This study concludes results of recent works of the researchers regarding the complex interaction among heat control, material and restraint intensity on the residual stress state in welded components. These analyses are extended by further experiments. Based on the obtained major effects, an approach for a welding residual stress assessment regarding component design according to prevailing standards for crane construction, an important application for high-strength steels, is presented. KW - Process parameters KW - Residual stresses KW - MAG welding KW - Restraint KW - High-strength steels PY - 2017 U6 - https://doi.org/10.1007/s40194-016-0394-9 SN - 0043-2288 SN - 1878-6669 VL - 91 IS - 1 SP - 91 EP - 106 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-39044 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Load analyses of welded high-strength steel structures using image correlation and diffraction techniques N2 - In an increasing number of modern steel applications, high-strength structural steel grades are demanded to meet specifications regarding a high load-bearing capacity and a low operating weight. Lightweight design rules enhance the safety requirements, especially for welded joints. Besides a higher cracking risk for high-strength steel welds, the formation of tensile residual stresses might lead to fracture due to overloading or premature failure if not adequately considered. In this study, a stress-strain analysis was conducted at component-related structures from S960QL using digital image correlation while preheating, welding and cooling adjacent to the weld seam. X-ray diffraction analysis of the local residual stresses in the weld seam showed a good comparability with global analyses using either a DIC system or a special testing facility, which allowed in situ measurements of welding loads. By analysing two different seam geometries, it could be shown that lower multi-axial stresses arise if a narrower weld groove is used. Comparative analyses revealed a direct correlation of the local residual stresses in the weld with transverse shrinkage restraint, whereas the residual stress level in the HAZ is significantly affected by the bending restraint of the weld construction and the occurring bending stresses, respectively. KW - Process parameters KW - Residual stresses KW - Restraint KW - GMAwelding KW - High-strength steels PY - 2018 U6 - https://doi.org/10.1007/s40194-018-0566-x SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 3 SP - 459 EP - 469 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-44270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schroepfer, Dirk A1 - Hannemann, Andreas T1 - In-situ Observation of Stress Evolution and Cracking during High Strength Steel Welding N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system with a load capacity of 2 MN specifically developed for online monitoring of stress formation and cracking are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be quantified in-situ during welding and post weld heat treatment. Examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. Elevated working temperatures significantly increase the tensile residual stresses in the heat affected zone (HAZ). The effect of mechanical stresses resulting from welding on stress relief cracking is demonstrated by the example of a creep resistant steel. Reheat cracks were monitored online during post weld heat treatment. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Residual stress KW - Restraint KW - Welding KW - Large-scale test KW - Reheat cracking PY - 2019 SP - 83 EP - 84 PB - SEIEI Printing Co., Ltd CY - Osaka, Japan AN - OPUS4-49773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Formation of multi-axial welding stresses due to material behaviour during fabrication of high-strength steel components N2 - Today, an expanding application of high-strength steels in modern welded constructions can be observed. The economical use of these steel grades largely depends on the strength and reliability of the weldments. Therefore, the special microstructure and mechanical properties of these grades have to be taken into account by keener working ranges regarding the welding parameters. However, performance and safety of welded components are strongly affected by the stresses occurring during and after welding fabrication locally in the weld seam and globally in the whole component, especially if the shrinkage and distortion due to welding are restrained. Some extensive studies describe the optimization of the welding stresses and the metallurgical effects regarding an adapted welding heat control. Lower working temperatures revealed to be particularly effective to reduce the local and global welding-induced residual stresses of the complete weld significantly. However, decreased interpass temperatures cause concurrently higher stresses during welding fabrication. This work shows strategies to reduce these in-process stresses. With help of multi-axial welding stress analyses in component-related weld tests, using a special 2-MN-testing facility, differences in stress build-up are described in detail for root welds, filler layers and subsequent cooling to ambient temperature. KW - Residual stresses KW - GMA welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2018 U6 - https://doi.org/10.1007/s40194-018-0650-2 SN - 0043-2288 SN - 1878-6669 VL - 63 IS - 1 SP - 43 EP - 51 PB - Springer AN - OPUS4-46604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Optimization of welding loads with narrow groove and application of modified spray arc process N2 - Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and welding processes becomes more challenging with increasing material strength and elastic ratios. High residual stresses are able to diminish lifetime, load capacity and component safety and should be avoided. Recent analyses have shown strong influences of heat control and restraint of the weld due to arising reaction stresses, superimposing with local residual welding stresses. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by power source manufacturers, which provide virtually similar features and several benefits, enabling welding of narrower seams with reduced weld volumes and total heat inputs. This research focuses on welding loads due to modified weld seams. The global reaction forces and moments and their superposition with local residual stresses in welded components due to external shrinkage restraints were investigated using a special testing facility and XRD. The restraint intensity, weld seam geometry and welding process were varied for statistical evaluations of resulting welding loads. When welding under restraint, a reduction of the weld seam volume causes significantly lower reaction stress levels. KW - Residual stresses KW - MAG welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2017 U6 - https://doi.org/10.1007/s40194-017-0484-3 SN - 1878-6669 SN - 0043-2288 VL - 61 IS - 6 SP - 1077 EP - 1087 PB - Springer CY - Berlin Heidelberg AN - OPUS4-41071 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Schaupp, Thomas A1 - Kannengießer, Thomas T1 - Welding stress control in high-strength steel components using adapted heat control concepts N2 - High-strength steels are increasingly applied in modern steel constructions to meet today’s lightweight requirements. Welding of these steels demands a profound knowledge of the interactions between the welding process, cooling conditions, heat input, and the resulting metallurgical occurrences in the weld and its vicinity. Additionally, welding stresses may be detrimental for the safety and performance of high-strength steel component welds during fabrication and service, especially due to the high yield ratio. For a development of strategies to adjust welding heat control, all these effects should be considered, to reach a complete exploitation of the high-strength steel potential. In recent researches at BAM, multilayer GMAW experiments were performed with high-strength steels, in which cooling conditions and resulting microstructure were analyzed for varied heat control parameters. The application of a unique 3d-operating testing facility and X-ray diffraction measurements allowed the analysis of local stresses in the weld while welding and cooling under component relevant shrinkage restraints. As a result, correlations between material behavior, welding, and cooling condition and the arising multi-axial stresses and forces were found. Based on this study, statements for the development of adapted heat control concepts were derived, which are presented by means of specific analysis examples. KW - Residual stresses KW - GMA welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2019 U6 - https://doi.org/10.1007/s40194-018-00691-z SN - 0043-2288 VL - 63 IS - 3 SP - 647 EP - 661 PB - Springer AN - OPUS4-48006 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -