Analysis of Plane Stress Ductile Fracture Propagation by Simulating Necking

Fracture experiments at room temperature on full-scale specimens fabricated from relatively thin plates of HSLA-80 and EH-36 ship steel consistently show the development of the plastic limit load on the net section and ductility greater than times yield strain, despite large fatigue cracks. A limit-load analysis can accurately predict the load at any point in the deformation if the crack length is known. Predicting crack extension using a constant crack-opening angle is a simple and reasonably accurate approach. The difficulty is in predicting the onset of extension after the development of strain localization. A simple approach using conventional small-strain finite-element analysis and a special "necking" stress-strain curve that is calibrated from conventional tensile test data is proposed. This approach gives very good predictions of the onset and propagation of ductile tears, including the spread of plasticity to the gross section.