The Influence of Irregularities in the Crack Shape on the Crack Extension Measurement by Means of the Direct-Current-Potential-Drop Method

摘要

The equations used for calculating the crak extension from the cange in the potential drop at a fracture mechanics specimen are generally drived for perfectly straight crack fronts. In the practice of fracture mechanics tests the crack, however, usually grows faster in the interior ofthe specimen than at the exterior, leading to a curved crack front. For such a case we calculate the potential drop by means of a finite difference scheme. It is shown that for cuved cracks the usual procedure of the direct-current-potential-drop method underestimates the real crack extension. The same finite difference scheme is then used to account fr conductive bars and bridges, which sometimes are left behind the crack front. Finally, the influence of side grooves on the potential drop is investigated.