Universal characterization of three-dimensional creeping crack-front stress fields

Abstract

Creeping fracture in engineering always occurs in high temperature structures with complicated geometries and loading configurations, and how to characterize the three-dimensional crack border stress fields is essentially important to design of the structures. By comprehensive finite element analyses of specimens with through-the-thickness cracks and specimens with corner, surface and embedded elliptic cracks, we demonstrated that a three-parameter characterization based on C(t) integral, the out-of-plane stress constraint factor Tz and in-plane constraint coefficient Q* can be efficiently applied in all cases. It is shown that a two-parameter C(t)–Tz solution can provide efficient prediction for the stress field ahead of the crack under small scale creep condition. Under large scale creep conditions, it is found that Tz has nearly a unified distribution ahead of cracks, and the three-parameter C(t)–Tz–Q* solution can characterize the crack front stress fields efficiently. This universal characterization of the creeping crack front stress field should serve as a solid fundamental for three-dimensional damage tolerant design of high-temperature structures.