The relationship between Ct and contour integrals under small-scale transient creep

In this paper, the relationship between the Ct and contour integrals for small-scale transient creep conditions is established, via elastic-creep finite element analysis. It is found that the Ct integral is similar to the contour integral value evaluated roughly at the creep zone size defined as the boundaries where time-dependent effective creep strains equal the instantaneous effective elastic strains and measured normal to the crack plane at the crack tip.