Mechanically Based Crack Growth Experiments

To ascertain the existence of an OAR ahead of the tip of a growing crack and to determine which elements might be oxidized there, mechanically and chemically based, interrupted crack growth experiments were carried out. The findings from these experiments are summarized below. 

A molecular transition model involving the -relaxation in PMMA has been first put forward by Johnson and Radon They explained the transition in crack speed behavior based on a correlation between the temperature dependence of a time to failure inferred from fracture experiments and the temperature variation of the reciprocal frequency of the P-relaxation peak. They thus assumed that the crack transition is caused when the P-process is fully active. Also the fracture mechanics parameter K, governing the transition from slow to fast crack growth, shows a time and temperature dependence equal to that of the p-transition... 

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