Abstract
Fatigue crack growth modeling was performed for Ti–6Al–4V forged materials failed by subsurface crack generation at cryogenic temperatures. The modeling that was based on linear fracture mechanics under the Mode I condition provided a good estimate of the stress intensity range of subsurface or surface and fatigue crack growth, enabling the estimation of the crack propagation life. The fatigue crack growth rate calculated using the Paris rule, da/dN=C(ΔKI)m, almost corresponded to the one obtained from the analysis of the striation on the fracture surface. The calculated crack propagation life was less than a tenth of the number of cycles to failure over 106. As a result, the subsurface crack initiation (Stage I crack generation) process consumed a large number of cycles to failure—as many as that at a lower stress level.
