DUCTILE FRACTURE OF HY-100 AND HSLA-100 STEELS AS A FUNCTION OF STRESS STATE

摘要

Failure of two high strength Navy steels, HY-100 and HSLA-100, have been examined as a function of stress state using notched and unnotched axisymmetric tensile specimens. The failure strains of both steels decrease in an exponential manner with increasing stress triaxiality. The magnitudes of the failure strains are also sensitive to the material chemistry, particularly with regard to the addition of Ca as an inclusion shape modifier. Two failure mechanisms are identified: a global damage accumulation process involving coalescence of relatively equiaxed voids and a void-sheet process which links large, elongated inclusion-initiated voids by a shear instability. The void-sheet mechanism intervenes and limits ductility at high stress triaxialities in the HY-100 steel when it is oriented such that the elongated inclusions are normal to the tensile direction.