Material modelling to determine material properties in numerical welding simulation

• Applicant: Dr.-Ing. Thomas Nitschke-Pagel, since 5/2024
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 471313862

Arc welding is one of the main process methods to join components made of the increasingly used lightweight steels such as ultra-high strength steel S960 and advanced high-strength steel TRIP700 in manufacturing industries. Nevertheless, residual stress and distortion are unavoidably generated in weldments because of the inhomogeneous temperature field induced by arc heat input. To obtain the proper mechanical performance of the welded structures, numerical simulation has been used to predict the temperature field, residual stress, and distortion for the optimization and design of the welding procedure. Material modelling is one of the major issues in numerical simulation. One of the main purposes of material modelling is to appropriately determine the data of material (thermal and mechanical) properties of a given material, which can be obtained from various methods such as experimental method. However, it is still unknown how to choose the economical and reliable method to determine the material properties of a given material in numerical welding simulation. Therefore, it is necessary to conduct sensitivity analyses to investigate the influence of the variation in material properties obtained from different methods on the predicted welding temperature field, residual stress, and distortion. As fundamental research, numerous welding simulation cases will be elaborately designed to systematically study the effect of material properties on the calculated temperature field, residual stress, and distortion. Material tests will be performed to measure the material properties of the given materials for comparison. Besides, welding experiments will be carried out to measure thermomechanical results for validation. Based on the experimental and numerical results, the influence of material properties on the calculated welding temperature field, residual stress, and deformation will be clarified. Furthermore, it will be clarified whether the effect of material properties on the predicted temperature field, residual stress, and distortion in thin-plate weldments is similar to that in thick-plate weldments in numerical simulation. The variation range of the predicted thermomechanical results induced by the variation in the material properties will be revealed, which is very helpful for the analysis of the divergence between the predicted and experimental results. The reliability of the provided empirical equations to assess the material properties mainly deduced from mild steels and conventional high strength steels for lightweight steels S960 and TRIP700 will be evaluated. Besides, these input variables on the thermal and mechanical properties will be in the order of importance, which is critical for the accurate prediction of welding temperature field, residual stress, and distortion in numerical simulation. In addition, a guideline will be provided for the effective and reasonable determination of material properties in numerical welding simulation.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr.-Ing. Jiamin Sun, Ph.D., until 5/2024