Project Details
Projekt
Multiscale thermoplastic analysis in the solidification zone
Subject Area
Mechanics
Joining and Separation Technology
Joining and Separation Technology
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 434946896
As a flexible and contact-free joining technology, laser beam welding has increasingly gained importance. Processing of alloys with large melting range poses a challenge due to their solidification cracking tendency. Solidification cracks form due to critical stress and strain states of the dendritic microstructure with interdendritic melt. Despite the high industrial relevance, there are only approaches addressing single aspects of the problem, metallurgically or structurally oriented. The research unit “Solidification Cracking during Laser Beam Welding – High Performance Computing for High Performance Processes” aims at developing quantitative process understanding of the mechanisms of solidification cracking and their relation to process parameters.Since a full-field resolution of the dendritic microstructure with interdendritic melt, taking into account the physical mechanisms prevailing here, would lead to immensely large systems of equations that do not allow efficient simulation of the process, a direct homogenization method, the FE²-method, is applied. This establishes a link between the dendritic solidification zone on the microscale and the macroscale on the component level. In close cooperation with TP 5 this project is dedicated to multi-scale and multiphysical modelling of the processes in the mixture zone in the forefront of the solid-liquid interface, where the critical zone for the formation of solidification cracks is located. In the multi-scale approach of the FE²-method for thermomechanically coupled problems, at each macroscopic integration point microscopic boundary value problems (in the form of representative volume elements, RVEs) are attached and solved under energetically consistent boundary conditions and the associated material response on the macroscale is obtained through evaluation of suitable surface integrals of the RVEs. To reduce the complexity of the RVEs, statistically similar representative volume elements (SSRVEs) are used, whose construction is based on the phase field simulations of the dendritic microstructure of TP 6. By means of thermoplastic material laws, the material behaviour of the individual phases is recorded on the microscale. The modelling on the macroscale demands the consideration of the influence of the laser beam as well as further boundary conditions, which are incorporated from the other subprojects. The efficient implementation of the multiscale approach requires the cooperation especially with the applicants Klawonn/Lanser, which enables the use of the algorithms on high performance computers. This approach allows a predictive analysis of the formation of solidification cracks on the basis of local state variables of the microstructure as a function of macroscopic process parameters.
DFG Programme
Research Units
