Simplified Estimation of Creep-Rupture Strength for Notched Tensile Specimens of Austenitic Stainless Steels

Abstract

A method for characterizing the creep-rupture strength of notched tensile specimens subjected to constant membrane loading has been developed. This method resolves the apparent contradiction between notch-strengthening and notch-weakening by employing the average von Mises equivalent stress on the net section of a notched specimen as its true rupture strength. The nominal net section equivalent stress can be determined by elastic analysis. Seven different notched specimen geometries of 304 and 316 stainless steel, assessed by this approach, exhibit varying degrees of notch-weakening at test temperatures from 1000°F (538°C) to 1500°F (816°C). The extent of notch-weakening is slightly dependent on specimen material and test temperature but the principal factor appears to be the degree to which the notch constrains inelastic flow on the net section. The effects of notch constraint on notch-weakening are well characterized by the peak stress triaxiality factor.