抄録
A systematic criterion on ductile fracture is proposed for metallic materials with not only a high ductility but also a reducing ductility under intense neutron irradiation or under other environments, because a ductile fracture strength is a key limiting strength for assuring the structural integrity of reducing ductility components. To develop the criterion, a true stress-true strain correlation (a constitutive equation) shall be formulated over the strain range to fracture. When a significant hardening, typically a drastic increase in yield strength, is caused by neutron irradiation or by cold rolling, Swift's equation is found to suitably correlate experimental data on stress-strain curves, by adjusting a prestrain ε_0 to the hardening effects. Concerning the ductile fracture criterion, it is not easy to develop that, because the ductile fracture mechanism is very complicated. The authors show that the fracture condition is approximated reasonably on the safe side by a condition on onset of local necking, and then propose the fracture criterion.
