Experimental investigation of the yielding process of a ductile polycarbonate cylinder subjected to line loading using digital image correlation

Abstract

The yielding formation and propagation of a ductile polycarbonate cylinder subjected to line loading, which corresponds to the global behavior of the structure, was experimentally studied and evaluated by measuring the strain fields on the end of the cylinder using Digital Image Correlation. The global behavior of the structure is expressed by a relationship between the average stress (load divided by contact area) and the equivalent strain (ratio of half width of contact area to radius of the cylinder); the contact area was measured in the same experiment by analyzing the images of the compressed pressure film captured through a transparent plate below the cylinder. A correspondence between the yielding state and the nonlinearity of the global behavior was constructed and, as loading was increased, the cylinder was found to first yield at a specific point after which a yielding core formed and propagated. Before the yielding core propagated to the surface of the cylinder, the global behavior of the structure remained linear, although the cylinder was no longer homogeneous and the material was nonlinear. After the yielding core propagated to the surface of the cylinder, the propagation was accelerated and the global behavior became nonlinear. The correspondence constructed in the paper will be helpful to understand the failure process and to evaluate the carrying capacity of a ductile polycarbonate cylinder subjected to line loading.