Creep-fatigue crack growth is an important failure mechanism for materials operating at high temperatures. While crack growth laws have been developed for hold-time loads and constant-amplitude cyclic loads, load transients must also be considered for determining component lifetimes. In this study, computational fracture mechanics simulations are used to study crack growth in two nickel-base superalloys at elevated temperatures following overloads. The computations demonstrate that post-overload crack growth depends strongly on the magnitude of crack-tip viscoplastic deformation in the bulk material. In some cases, a classical retardation effect is absent. Dynamic recovery and hardening due to viscoplastic strain gradients are also shown to influence post-overload crack-tip fields and crack growth.
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