The failure of ductile plates containing thin ligaments

A series of tensile tests on mild steel plates containing partially penetrating defects is described. In the tests both the thickness of the ligament and the length of the crack were varied. The experiments determine the load and crack-opening-displacement (COD) at ligament failure, and the subsequent mode of plate failure. The loading was displacement controlled and three modes of failure were observed: 1. Ligament failure followed by plate failure at higher load. 2. Ligament failure followed by plate failure at lower load. 3. Simultaneous failure of ligament and plate. A relation is established between the COD at ligament failure and the ligament thickness. This relation is used in conjunction with a reference stress technique to predict the load at which ligament failure occurs. The mode of failure and the loads at failure predicted in this way are in good agreement with the experimental results. (orig.)