Experimental Study on the Effect of Shot Peening and Re-Shot Peening on the Residual Stress Distribution and Fatigue Life of 20CrMnTi

Abstract

As a surface peening technique, shot peening introduces residual compressive stresses to the surface of the part, which effectively increases the fatigue life of the structure and material. However, when structures are subjected to alternating loads, this can lead to stress relaxation on the material surface, weakening the effectiveness of the shot peening process. In addition, reasonable shot peening parameters are essential. In this paper, the effects of shot peening pressure and shot coverage on the fatigue life of materials during shot peening were investigated, followed by fatigue tests on 20CrMnTi specimens using a high-frequency fatigue testing machine to study the effects of shot peening and re-shot peening on the fatigue life of shot-peened materials after different load cycles. The results show that a reasonable shot peening pressure and coverage rate can significantly improve the fatigue life of the material, while a shot peening pressure higher than 0.4 MPa will reduce the fatigue life of the material 20CrMnTi. Coverage rates of 100% and 200% can both improve the fatigue life of the material, while a 200% coverage rate has a better strengthening effect. Re-shot peening removes the residual compressive stress relaxation on the surface of the material caused by cyclic loading and improves the fatigue life of the material. The maximum value of the residual compressive stress on the surface of the test material after shot peening is 443 MPa, and after a certain number of fatigue loads, the residual compressive stress on the surface is reduced to 203 MPa, which is subjected to secondary shot peening, and the residual compressive stress is restored to 415 MPa, and the fatigue life is significantly increased. When the second shot peening time is taken as 25% of the fatigue life of the initial shot blasting of the material, the shot peening effect is better.