Predicting the ductile failure of DP-steels using micromechanical modeling of cells

Thus far, micromechanical modeling of cells has been used successfully to capture the deformation behavior of dual phase (DP) steels, which display impressive mechanical properties, especially for the automotive industry. However, the prediction of ductile failure, which is essential in the manufacture and design of parts, needs to be modeled in order to develop a model, which can fully characterize DP-steels. The Gurson - Tvergaard (GT) damage model is coupled with a micromechanical model developed in earlier works, which captures the deformation behavior of DP-steels well, making a complete material model. A procedure that accounts for damage in terms of the void volume fraction, stress triaxiality and the mechanics of failure in DP-steels as major damage factors, is developed in this work to determine the calibrating parameters in the GT yield function. When these parameters are determined, they are employed in numerical simulations of a tensile bar test to compare the experimental and numerical fracture parameters. The results show good agreement between the numerical predictions using the GT parameters obtained by the procedure developed in the current work and the experimental findings at different levels of volume fraction of martensite (V_m). It is also shown that the GT parameters obtained using a calibrating procedure, which ignores the local deformation behavior of the material, does not produce the appropriate parameter values.