Highly Scalable Two-level Monolithic Overlapping Schwarz Preconditioners for Thermo-elastoplastic Laser Beam Welding Problems

A thermo-elastoplastic finite element approach is used to perform the simulation of a laser beam welding (LBW) process. This results in a nonlinear, nonsymmetric saddle point multiphysics system, for which the nonlinearity is handled via the Newton method. The iterative solution of the arising linear system is accelerated by using robust and highly scalable, overlapping Schwarz domain decomposition preconditioners. It is well-known that a one-level method of this type is not scalable and therefore a second level has to be added. Therefore, the construction and numerical analysis of monolithic, two-level overlapping Schwarz preconditioners with different variants of the GDSW (Generalized Dryja-Smith-Widlund) coarse space are presented here. A new and parallel efficient implementation of several variants of GDSW, that is, GDSW, RGDSW, and GDSW*, in PETSc, is introduced, which is usable for multiphysics problems, as, for example, the thermo-mechanical LBW problem considered here. Different combinations of the GDSW variants for the different fields (temperature and displacements) are compared and parallel scalability for realistic problems is shown.