Evaluation of true stress–strain diagrams for welded joints by application of Digital Image Correlation

Abstract Digital Image Correlation (DIC) is applied to evaluate stress–strain diagrams for welded joints in two different ways. The first one is based on the measures strains along the welded joint, including all 3 zones of interest, base metal (BM), weld metal (WM), and heat-affected-zone (HAZ) subdivided into fine grain (FG) and coarse grain (CG) subzones. Specially designed iterative procedure has been used to determine coefficient of Holomon law to get true stress–strain curves for welded joint made of HSLA steel Niomol 490. The second one presents new methodology for evaluating true stress–strain diagram, based on measured values of contraction, as obtained by 3D DIC, rather than more conventional analytical formulas. New methodology is applied to undermatched welded joint, made of martensitic steels X10 CrMoVNb 9–1.