Development and Application-oriented Validation of a Reliable Smoothed Particle Hydrodynamics Discretization for Solids to describe Friction Stir Welding

• Applicants: Professor Dr.-Ing. Peter Eberhard; Professor Dr. Siegfried Schmauder
• Subject Area: Mechanics
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388107621

This research is a second phase of the project, devoted to the accurate simulation of the friction stir welding (FSW) process by means of the Smoothed Particle Hydrodynamics (SPH) method. FSW is a solid state welding process, which is described by multiple interdependent physical phenomena, including plasticity with high strains and strain rates, inelastic heat generation, friction, and solid state bonding. The SPH discretization method, with its meshless nature, provides a framework, which is capable of dealing with large deformations and various physical effects.In the first phase of the project, a novel physically based material model was developed and implemented in order to provide an improved material behavior description specific for FSW. The issue of the particle orientation was also investigated, resolved and tested, followed by the documentation in form of a publication. As a part of the second package, a research on discretization-error based adaptivity in SPH was conducted, providing an original strategy dealing with particle refinement and coarsening.The overall objective of the second phase of the project developed from the first phase. To achieve a major improvement of the SPH formulation for solids, and by these means not only to provide a precise simulation of FSW, but also to develop a reliable, innovative simulation technique, which is able to deal with the simulation of a wide range of industrial applications. Due to the fact that FSW combines variable characteristics, which are also common for many other industrial processes, it offers a sufficient background for a later transfer of he research results.As the time frame of the preceding project was shortened and did not allow to deal with all the aspects in full, they are translated into this project. Some final improvements of the material model by including precipitation hardening and validation of adaption of the discretization are to be accomplished, as well as the development of a material bonding criterion are to be performed in full. Additionally, during the first part of the project, further areas of research were determined. These include an improved SPH stabilization formulation, extension of the friction model based on material behavior, and enhancement and validation of the thermal behavior model. As a final step, the improved SPH solid formulation will be applied to the FSW process in order to predict the final joined geometry, quality of the weld, and microstructural behavior. The precision of the prediction will be examined through comparison with experiments conducted by the IMWF.

• DFG Programme: Research Grants