Ingenieurwissenschaften und zugeordnete Tätigkeiten
Filtern
Dokumenttyp
- Vortrag (30)
- Zeitschriftenartikel (20)
- Beitrag zu einem Tagungsband (4)
- Posterpräsentation (1)
Sprache
- Englisch (55)
Schlagworte
- Residual stresses (55) (entfernen)
Organisationseinheit der BAM
- 9 Komponentensicherheit (32)
- 9.4 Integrität von Schweißverbindungen (29)
- 9.2 Versuchsanlagen und Prüftechnik (23)
- 9.0 Abteilungsleitung und andere (6)
- 5 Werkstofftechnik (3)
- 8 Zerstörungsfreie Prüfung (3)
- 8.5 Röntgenbildgebung (3)
- 5.3 Polymere Verbundwerkstoffe (2)
- 9.3 Schweißtechnische Fertigungsverfahren (2)
- 5.0 Abteilungsleitung und andere (1)
Eingeladener Vortrag
- nein (30)
WAAM process influences on local microstructure and residual stresses in high-strength steels
(2021)
High-strength fine-grain structural steels have great potential for weight optimization of many modern engineering structures. Efficient manufacturing can be achieved here above all by Wire Arc Additive Manufacturing (WAAM). First commercial high-strength welding consumables for WAAM are already available. Due to a lack of knowledge and guidelines for the industry regarding welding residual stresses and component safety in manufacturing and operation, their application is still severely limited. Residual stresses play a crucial role here, as the special microstructure of high-strength steels is sensitive to cold cracking.
For this reason, process- and material-related influences, as well as the design effects on residual stress formation, are being investigated in a project funded by the AiF (FOSTA P1380/IGF 21162 BG). This study focuses on determining the interactions between heat control during WAAM process, resulting hardness, microstructure, and residual stresses, analyzed by X-ray diffraction. Welding experiments using geometrically similar AM specimens show that, with regard to the heat input, the energy per unit length in particular leads to significantly affected cooling times and microstructures and causes pronounced localized effects in terms of residual stresses in the upper weld beads.
WAAM process influences on local microstructure and residual stresses in high-strength steels
(2021)
High-strength fine-grain structural steels have great potential for weight optimization of many modern engineering structures. Efficient manufacturing can be achieved here above all by Wire Arc Additive Manufacturing (WAAM). First commercial high-strength welding consumables for WAAM are already available. Due to a lack of knowledge and guidelines for the industry regarding welding residual stresses and component safety in manufacturing and operation, their application is still severely limited. Residual stresses play a crucial role here, as the special microstructure of high-strength steels is sensitive to cold cracking.
For this reason, process- and material-related influences, as well as the design effects on residual stress formation, are being investigated in a project funded by the AiF (FOSTA P1380/IGF 21162 BG). This study focuses on determining the interactions between heat control during WAAM process, resulting hardness, microstructure, and residual stresses, analyzed by X-ray diffraction. Welding experiments using geometrically similar AM specimens show that, with regard to the heat input, the energy per unit length in particular leads to significantly affected cooling times and microstructures and causes pronounced localized effects in terms of residual stresses in the upper weld beads.
Stresses in repair welding of high-strength steels Part 2: Heat Control and Stress Optimization
(2023)
In welding of high-strength steels, e.g., for foundations and erection structures of wind energy plants, unacceptable defects can occasionally be found in the weld area, which should be removed by thermal gouging and subsequent re-welding. High shrinkage restraint of repair welds may lead to crack formation and component failure, particularly in interaction with degraded microstructures and mechanical properties due to repair cycles. This study aims for elaboration of recommendations for repair concepts appropriate to the stresses and materials involved to avoid cold cracking, damage and expensive reworking. In part 1 [1] of this study systematic investigations of influences of shrinkage restraint on residual stresses and cold cracking risk during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures were focussed. In this part 2, the microstructure and residual stresses due to gouging and influences of heat control parameters in repair welding are analysed. A clear reduction in residual stress after gouging can be observed, especially for the specimens with restrained transverse shrinkage. Gouging to a depth of approx. 2/3 of the seam height does not lead to a complete relaxation of the observed reaction forces. Particularly for the higher strength steel S960QL, there are pronounced areas influenced by the gouging process in which a degradation of the microstructure and properties should be assumed. Overall, the repair welds show a significant increase in the width of the weld and HAZ compared to the original weld, especially in the case of S960QL/G89. The repair welds show higher welding-induced stresses than the original welds, especially in the areas of the HAZ and the base metal close to the weld seam. This behaviour can be attributed overall to increased restraint conditions due to the remaining root weld or shorter gouge grooves. In good agreement with earlier investigations, the residual stresses transverse to the weld can be significantly reduced by upwardly limited working or interpass temperatures and the reaction stresses resulting from high restraint conditions can be effectively counteracted. The influence of the heat input on the stress formation is low compared to the interpass temperature for both test materials.
The presentation provides a discussion and damage tolerant assessment of metallic AM components. In the focus are problems of the determination of representative material data, the effect of material defects and residual stresses. Starting with the actual state-of-the-art in the field, options and possibilities of a damage tolerant design for AM are discussed.
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.