Intermittent Crack Growth In Fatigue

Fatigue occurs under cyclic loading at stresses below a material's static strength limit. We consider fatigue crack growth as a stochastic process and perform crack growth experiments in a metal (copper). We follow optically cracks propagating from initial edge notches. The main interest is in the dynamics of the crack growth-the Paris' law and the initiation phase prior to that-and especially the intermittency this is discovered to display. How the sampling of the crack advancement, performed at regular intervals, influences such measurement results is analysed by the analogy of planar crack dynamics in slow, driven growth.