True Stress-strain Curves for HSLA Steel Weldment – Iteration Procedure Based on DIC and FEM

Abstract True stress-strain curves of HSLA steel welded joint regions were estimated by using numerical simulation of strains measured by DIC and special iteration procedure to match the results. Strains were measured at certain level of loading in all regions of welded joint with different tensile properties, namely base metal (BM), weld metal (WM) and two subzones of Heat-Affected-Zone (fine grain, FGHAZ, and coarse grain – CGHAZ). By converting engineering stress (load divided by initial cross section area) into true stress, experimental true stress-true strain curves are obtained and used as initial iteration for the Finite Element Method (FEM) simulation, after being fitted by the power law relation for stress-strain curves. Obtained results are then compared with the experimental results to find the differences and make appropriate correction in power law curves and make as many iterations as needed before the differences become small enough. This procedure has been verified by an example of welded tensile panel.