Effect of collision energy on plastic deformation under repeated impacts

Abstract

Metal materials were found to undergo substantial cumulative plastic deformation while operating under ultra-low stress, repeated-impact conditions that were far below the yield points of the materials. Plastic deformation was not only related to stress, but also to the collision energy input. Low-energy, repeated-impact tests were carried out on YT01 and 65Mn samples using a fatigue testing machine fabricated in-house. A grid method with coordinates, scanning electron microscopy, and single-crystal x-ray diffraction were employed to study the effect of the collision energy on the cumulative deformation, layer strains, and microstructures of the materials. The following results were obtained. For impact-induced stresses with the same peak value, a greater cumulative deformation and higher layer strain were observed for larger collision energy inputs. The collision energy tended to have a more significant influence on deformation at locations closer to the surface. For the same collision energy, a greater cumulative deformation occurred as a result of the higher peak impact stress. The location at which the deformation terminated was related to the peak impact stress but unrelated to the collision energy. Analysis also revealed that as the collision energy increased, the sub-grains in the microstructure of the materials decreased in size, while the micro-strain increased. In conclusion, the collision energy was an important factor affecting the cumulative plastic deformation in repeated-impact collisions.