Damage accumulation and failure of HSLA-100 steel

Damage accumulation in the form of the volume fractions and number densities of strain-induced voids has been experimentally characterized for HSLA-100 steel subjected to tensile failure over a range of stress-states (stress triaxiality ratios of 0.8 to 1.4). The dependence of void volume fraction on strain indicates the presence of a void growth stage that is sensitive to stress-state in a manner that can be described by a relationship with the form that can be predicted by Rice and Tracey but with an increased dependence on stress triaxiality. The damage results also suggest a transition of stable void growth to rapid void growth and imminent material fracture at a critical void volume fraction that decreases slowly with increasing stress triaxiality ratio. A straight-forward analysis, based on the experimental observations, relates the observed experimental dependence of failure strains on stress triaxiality for this steel. The damage accumulation behavior of this steel, which fails due to the growth and coalescence of equiaxed voids, is also contrasted to that of HY-100 steel which forms elongated voids.