Two Parameters Describing Cyclic Hardening/Softening Behaviors of Metallic Materials

In this article, cyclic hardening/softening behaviors of metallic materials are studied by using 40 alloys' test results. In the analysis, two parameters are introduced: one parameter is new fracture ductility parameter; the other is cyclic hardening/softening factor. The new fracture ductility parameter expresses cyclic hardening/softening. According to the criterion, there are three critical values—2, 20, and 65.4%. When the new fracture ductility parameter is smaller than 2%, or ranges from 20% to 65.4%, the alloy behaves in a cyclic softening manner. However, when the new fracture ductility parameter ranges from 2% to 20%, or is greater than 65.4%, the alloy behaves in a cyclic hardening manner. The cyclic hardening/softening factor describes the degree of cyclic hardening/softening. If the cyclic hardening/softening factor is greater than 1, the material behaves in a cyclic hardening manner. But if the cyclic hardening/softening factor is smaller than 1, the material behaves in a cyclic softening manner. The more the cyclic hardening/softening factor deviates from 1, the greater the degree of hardening/softening. Compared with the traditional criteria, on the one hand, the present criterion has no indeterminate range, while on the other hand, the cyclic hardening/softening factor quantitatively describes the degree of cyclic hardening/softening. Therefore,the two parameters provide a more descriptive way to describe cyclic hardening/softening behaviors for metallic materials.