Physical properties. Stress analysis of crazes at moving crack tips

The finite element method is applied to contours of craze zones in front of moving crack tips in polymethylmethacrylate (PMMA), measured by interferometry, in order to compute the stress distribution. In contrast to the constant stress assumed in the Dugdale model, a stress distribution is found with a maximum at the crack tip then a sharp decrease and a more gradual decline over the larger part of the craze length. Computed stresses as well as the Dugdale stress increase with increasing crack speed and, hence, decreasing loading time. Generally the results obtained are in good agreement with those already found for growing crazes at stationary crack tips.