Determination of mechanical properties of the weld line by combining micro-indentation with inverse modeling

This paper provides a comprehensive study on determination of mechanical parameters in the weld zone and heat affected zone (HAZ) by using the micro-indentation and inverse modeling techniques. In order to improve the simulation accuracy of finite element (FE) modeling for such complex welded structures as tailed-weld blanks (TWBs), it is critical to characterize the detailed mechanical properties of the weld line. Majority of existing works however took uniform properties of weld line, which could lead to insufficient simulation accuracy for the welded structures. In this study, the weld line will be divided into several different zones, including weld zone and heat affected zones (HAZs) according to their hardness measured. In the characterization process, the relationship of force versus depth in different weld zones is obtained from micro-indentation tests using the Vickers sharp indenter. Then, an axisymmetric two-dimensional (2D) FE model is constructed based on the power law constitutive model to simulate the elastoplastic response of each corresponding zone. Finally, the mechanical parameters in different zone are identified by using genetic algorithm (GA) to minimize the discrepancy between the experimental data and simulation results. To verify the presented method, the modeling results are compared with the experimental data obtained through both uniaxial tensile test and digital image correlation (DIC) of welded specimens. The results demonstrate that the obtained mechanical properties allow well correlating the simulation to the experiment with better accuracy than other methods reported in literatures.