Crack arrest plastic zone

During the dynamic crack growth, local heat generation takes place at the crack tip. If the temperature is high enough, a plastic zone is formed at the tip (Fig. 3) and its traces are the so-called "arrest lines" which appear on the fracture surface after... 

Initial Crack Generated Adiabatically. Below 160 K, only uncontrolled crack propagation is possible, at a velocity roughly one-third of the velocity of sound. The tip zone is heated adiabatically. The difference is a moving crack tip which involves different thermal conditions (18,19). If the temperature rises far enough to exceed brittle-plastic transition, the tip zone becomes plastic and stress relaxation can take place (20,21). When this initial crack no longer grows, the condition is kept frozen in an arrest zone, where Kic can be measured. 

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