Study the effect of martensite banding on the failure initiation in dual-phase steel

• Effect of martensite banding was investigated on the failure initiation in DP steel.
• Mini tensile test with DIC and bending test with EBSD measurements were done to identify failure initiation.
• In both microstructures, martensite cracking is the dominant failure initiation mechanism.
• XFEM is used to model the failure initiation in DP steel.
• Identified XFEM parameters are validated by numerical versus experimental comparison.

This work aims to study the effect of martensite banding on the failure initiation in dual-phase (DP) steel. A microstructure based approach using representative volume elements (RVE) is utilized to evaluate the microstructure deformation and the failure initiation on the mesoscale. Mini tensile test with digital image correlation (DIC) analysis was carried out and linked to local scanning electron microscopy (SEM) analysis to identify macroscopic failure initiation strain values. In situ analysis of bending test in SEM combined with electron backscatter diffraction (EBSD) measurements before and after the test showed that crack initiation occurs in martensite islands. Representative volume element (RVE) modeling combined with extended finite element method (XFEM) was applied to simulate martensite cracking on mesoscale. XFEM failure parameters have been identified based on local and macroscopic mini tensile evaluation applying classical J-Integral theory. The identified parameters were validated by comparing the predictions with the experimental results.