Modeling Fusion Welds: A Multi-Scale Submodeling Approach

TLDR: A transient non-linear multi-scale finite element heat flow-mechanical model to determine micro-residual stresses was developed and a strong dependence of micro residual stresses on grain size is clearly observed.

Abstract: The technological properties of fusion welds are formed due to the simultaneous effects of different physical phenomena which occur on different length scales. In the multi-scaled modelling method designed to make microstructure modelling more tractable, a fine meso sub-mesh resides in each element of a coarse macroscopic global mesh. Of the same manner, a fine micro sub-mesh resides in each element of a coarse mesoscopic global mesh. In this work, a transient non-linear multi-scale finite element heat flow-mechanical model to determine micro-residual stresses was developed. Thermal cycles calculated to predict macro, meso and micro-residual stresses, were imposed as load conditions. The numerical procedure was developed in a three-dimensional domain using the coupling DREAM.3D-ABAQUS, and the construction of ABAQUS user-defined subroutines. A non-standard domain decomposition method based on the concept of Representative Volume Elements (RVEs) was used to include the polycrystalline nature of the specimen. The micro-submodel developed to identify temperature, strain and stress contours at different step times, requires the meso temperature gradient information as prescribed driven (load) boundary conditions. A strong dependence of micro residual stresses on grain size is clearly observed.