Water jet peening (WJP) is a mechanical surface strengthening process, which can improve the residual stress (RS) of the peened surface and then improve the fatigue life of components. In this paper, erosion experiments are conducted to investigate the influence of peening parameters on erosion. On this basis, RSs induced by WJP are studied in relation to the peening parameters. In addition, the coupled Eulerian–Lagrangian (CEL) technique is used to model and simulate the dynamic impact process of WJP on Al6061-T6. The influence of peening parameters such as jet pressure p, jet traverse velocity v_f, and the number of water jet pass n on the modification of residual stress field (RSF) is examined by simulation and experiment. The influence of incidence angle α and water jet diameter d on RSF is also investigated by simulation. Results show that compressive RS σ_crs is a result of the action of water-hammer pressure alone. Furthermore, σ_crs increases with an increase in p, n and α. The optimal peening parameters for Al6061-T6 are found to be p = 60 MPa, v_f = 2000 mm/min, n = 4, α = 90 deg and d = 2.0 mm. Finally, the depth of compressive RS layer D₀ increases greatly with an increase in water jet diameter d and can reach 984 μm.

This article reveals the formation mechanism of surface topography and the formation and coupling mechanism of residual stress field (RSF) after abrasive water jet sequential peening (AWJSP) that can sequential peening on the material surface at a certain distance interval, and proposes a mathematical model of surface dimple characteristic verified by simulation results. In addition, the influences of shot velocity v₀, shot radius R and the distance between the center of adjacent shots D_C on surface topography and RSF were also investigated. Results show the surface dimple forms resulting from the material plastic strain, and the residual stress (RS) is mainly induced by the unrecovered elastic strain resulting from the hindering of plastic strain. Decreasing v₀, R or D_C can decrease the surface roughness R_t, while increasing v₀ and R is beneficial to induce a large and deep compressive RS layer. D_C influences the whole distribution of compressive RS layer directly.

The water jet peening (WJP) technology can induce compressive residual stress (RS) in metal surfaces and, thus, improve the fatigue life of components. In this paper, a mathematical model is proposed for calculating the RS induced by WJP. To validate the proposed mathematical model, experimental and finite element simulation verifications were carried out on Al6061-T6. The distribution of RS along the depth direction, the maximum compressive RS, and the depth of the compressive RS layer were also investigated based on the mathematical model. Results showed that the error of maximum compressive RS between the mathematical model and experiment was within 9% under a jet pressure of 60 MPa, and the error of depth of the compressive RS layer between the mathematical model and experiment was within 13% under a jet diameter of 0.3 mm. Hence, the mathematical model is reliable and accurate. The maximum compressive RS increases with the increase in jet pressure, and the depth of the compressive RS layer approximately linearly increases with the increase in jet diameter.

In this paper, the theoretical models of the surface topography and residual stress (RS) were proposed, and the abrasive water jet sequential peening (AWJSP) finite element models were established by using ABAQUS. Then, the formation mechanism of the surface topography in multiple passes AWJSP process and the coupling mechanism of RS in a single and multiple passes AWJSP process were analyzed. After that, the influence of the number of shots (i.e. N), the distance between the center of adjacent shots D_c, shot velocity v, and shot radius R on the surface topography and residual stress field (RSF) of the target were investigated. Results show that successive dimples were formed by single-pass AWJSP, the RSF formed by the impact of each shot will influence the previous RSF, and that will be coupled with it. In multiple passes AWJSP process, decreasing D_c can decrease the surface roughness, the surface smoothness of the target material will gradually become better, and the RSF will also be uniform. Under full coverage condition, the surface roughness R_t and mean width of the profile R_sm will gradually decrease with the decrease of D_c, while the change of D_c has little influence on the RSF. Increasing the v can increase R_t and R_sm, and it is beneficial to induce a large and deep compressive RS layer. Increasing the R can decrease R_t, R_sm remains unchanged, and it is beneficial to induce a deep compressive RS layer.