Substrate Deformation Studies on Impact Erosion and Plowing by Photoelasticity

Static and dynamic photoelasticity methods were applied in studying the mechanisms of erosion. A multiple spark camera and a linear gas gun were used to photograph impact-induced dynamic stress waves. The propagation of stress waves in a polycarbonate material was analyzed upon impact of a 3-mm diameter rigid ball traveling at 50 m/s velocity. The role of pressure, shear, and Rayleigh waves in causing damage was found to be low. The residual stress field generated due to particle impact was determined using a circular polari scope. It was found that the plastic deformation at impact-induced high strain rates and the residual stress field generated by repeated impacts produce crack ing, and the interaction of these cracks results in erosion loss. Impact on brittle Columbia resin produced lateral, circumferential, and radial cracks, resulting in material removal. The stress gradient and cracking were also studied during plowing on the above two materials.