The Influence of Microstructure Heterogeneity on Crack Propagation in Welds Using XFEM

In this paper, the effect of local microstructural variation on the crack propagation is studied. The weldment sample is produced by bead-on-plate arc welding process. Resultant bead geometry and the equivalent heat source model are evaluated by the software SimWeld. Those data are imported to ABAQUS to regenerate the temperature field during welding. The volume fractions of product phases in the end are calculated at node using a well-known self-dependent metallurgical algorithm. Two tensile models using extended finite element method (XFEM) are established to analyze the crack growth. One model assumes uniform properties of base material in the whole weldment, while in the other model, the properties are obtained by interpolating with the local phase volume fractions. The power law is used to determine the crack opening. The differences in stress distribution and force-displacement curve demonstrate that the microstructure inhomogeneity does affect the crack propagation. Moreover, by interactively comparing the phase distribution and the crack path, it is found that the crack is incline to grow between the fusion zone (FZ) and heat affected zone (HAZ), where an abrupt change of microstructure happens.