Derivation of novel creep-integrated fatigue equations

Abstract

This manuscript presents a systematic derivation of novel creep-integrated fatigue equations that possess the following unique characteristics: (i) creep damage and creep-fatigue interaction damage are embedded into the fatigue equation and requires no deliberate computation; (ii) the embedded creep damage is formulated from the constitutive equation of creep; and (iii) the integrated equation is capable of modelling the full range of creep fatigue from pure creep to pure fatigue. These characteristics ensure that these creep-integrated fatigue equations are fundamentally sound, easy to use, and applicable over a wide range of creep fatigue conditions. The creep-integrated fatigue equations based on three constitutive equations of steady-state creep: Dorn equation, Larson-Miller equation, and Manson-Haferd equation are derived and successfully validated using two metals of vastly different creep and fatigue characteristics – the SS316 stainless steel and the Sn37Pb solder.