Comparison of Notched Bar Creep Behavior of Various Alloys

Possibility of creep rupture needs to be evaluated in design of various components operating at high temperatures. Multiaxial stress states need to be treated in many components and its proper consideration is of critical importance, in addition to the creep rupture behavior under uniaxial tension. In order to examine creep rupture behavior under high stress triaxiality, creep tests were conducted on notched bar specimens of various alloys used in power generation facilities. It was found that all materials showed notch-strengthening behavior but some materials showed considerable reduction of deformation at rupture, in comparison with the plain specimens. Its amount was not similar but strongly dependent on material, being larger in high chromium steels, and smaller in an austenitic stainless steel. It was found that the dependency of true rupture strain on temperature and inelastic strain rate in each material can be successfully modeled by a strain rate-temperature parameter.