Dependence of fracture ductility on thickness

Experimental and numerical study was performed on flat rectangular plates with a circular hole subjected to tensile load. Eighteen specimens with different thicknesses and different diameters of holes were tested all the way to fracture covering the range from plane stress to a full three-dimensional state of stress. These tests reveal that equivalent strain to fracture initiation increases with the ratio of thickness to ligament, reaches maximum and then decreases again. The effectiveness of shell elements in modeling fracture ductility was also evaluated. It is concluded that the shell element model is not suitable for plates with the ratio of thickness to ligament larger than 0.5. By comparing the results of tests and numerical simulations, some observations were made on the dependence of the equivalent strain to fracture on the stress triaxiality.