Numerical Model of Plastic Deformation on Cracked Surface under Repeated Pneumatic Impact

Abstract

Crack-closure treatment through repeated impact is supposed to be an effective, economical way to extend the fatigue remaining life for fatigue-affected structures with less damage. The material plastic behavior under repeated impact between chisel and material bodies was investigated, for the purpose of describing the crack-closure effect. A numerical model was established associating the impact depth with the number of impact times and device parameters, which is also proved by experiments. The material properties, after repeated impact, was determined via metallographic analysis and microhardness tests, indicating that the material will be hardened within a small affected zone due to the grain refinement caused by repeated impact. The finite-element method was used, as a supplementary approach, to investigate the relationship between impact depth and horizontal deformation on the cracked surface. A one-to-one linear relation was obtained, even under the different chisel tip parameters. Therefore, the contact of fracture surface, i.e. crack closure, can be predicted with the help of this numerical model and the aforementioned relationship.