Crack growth critical transition

Using equation (10.3), we can calculate the critical crack length Uf at which unstable or accelerated crack growth occurs (transition between regions II and III in figure 10.16). If we require that this crack length must not be exceeded,... 

The transition from slow to rapid crack growth, however, is relatively sharp for many polymers. This is exemplified by PMMA. At the critical value of stress intensity factor, Kj, a jump in crack speed is observed at the end of the slow growth region around 0.1 ms to much higher speeds which may be in the range of 10 to 100 ms , depending on testing conditions (e.g. With this jump is also associated a... 

For most experiments, hypothesis A appears to be an appropriate approach to evaluate a risk of failure except when the temperature T(t) sweeps across the glass transition temperature, which is about 143°C for the measurement of thermd expansion. In this case crack growth occurs far above the assumed critical value, which is especially the case during cooling from 170°C to... 

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