The extension of cracks at high temperature by growth and coalescence of voids

Abstract

The problem of creep crack growth is studied analytically in this paper. The analysis assumes a sufficiently slow crack growth rate so that elastic effects can be neglected and hence the near tip stress field is well approximated by the C*(HRR) field. The crack is assumed to advance continuously due to the growth and coalescence of voids directly ahead of the crack tip. An exact solution for the entire growth historya(a), 0 ⩽a < ∞, is obtained as a function of crack extensiona andC* for a wide variety of void growth mechanisms. The solution shows that, for a finite nucleation zone with sizeR, the steady state crack extension rateass =a(a → ∞) is attained exponentially fast with characteristic distanceR. Another consequence of the solution is that is proportional toC*. An important result is that, for crack extensiona less thanR, the transient crack growth ratea(a) can be approximated by a closed form asymptotic series.