Mechanical response of an high-strength automotive steel at different strain rates and evolution of damage-related parameters

The present work concerns a thin sheet high-strength steel of interest for automotive applications. The extended constitutive curves in static and dynamic conditions were determined by tensile tests on smooth specimens. Further tests carried out on notched specimens were simulated both to validate the elastoplastic response and to analyse the evolution of the relevant parameters related to ductile damage (triaxiality and Lode angle) in the critical areas of the specimens (diffuse and localized necking), studying the correlations between the trend of these quantities and the mode/location of the fracture initiation. The analysis of the images of the specimens acquired during the tests allowed to characterize in detail the behaviour of the material up to breakage, also providing different experimental references to validate the numerical simulations of the tests on the smooth and notched specimens.