A simple fracture mechanics based Charpy-V impact energy criterion for plastic collapse

Charpy-V based design methods usually provide advice on the relation between design temperature and some Charpy-V transition criterion. Thus, the methods try to safeguard against brittle fracture. Usually, methods are limited to small plasticity where the stresses are below yield strength. Sometimes, it may be important also to ensure that the structure sustains loads up to the plastic limit load. In this case the design is based on plastic collapse. So far, no simple methods to evaluate plastic collapse based on the Charpy-V test have been developed. Here, a simple fracture mechanics based plastic collapse criterion for Charpy-V impact energy is presented. The criterion contains a requirement on impact energy and temperature, both of which must be fulfilled to ensure achievement of plastic limit load. The criterions are given in the form of simple analytical functions and they account for yield strength, strain hardening and section thickness.