Contribution of Stable Crack Extension to Variable Amplitude Fatigue Crack Growth

What is it about?

Static fracture starts with stable crack growth typically proportional to the plastic zone created by increasing load that at some point turns unstable, leading to catastrophic failure. Cyclic loading induces crack growth by fatigue. Engineering practice involves variable cyclic load conditions whereby a crack can grow under small load cycles but also periodically encounter overloads. Surprisingly, prevailing methods to model crack growth ignore the inevitable additional quasi-static crack extension caused by an overload that induces a sudden increase in plastic zone size. This work describes how stable crack growth component can be accounted for in analysis of variable-amplitude fatigue.

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