Experiments and numerical simulations on fatigue properties of laser shock peening for FV520B steel

Abstract

Laser shock peening (LSP) experiments, low cycle fatigue experiments, microhardness and residual stress measurements, and scanning electron microscopy (SEM) analyses were conducted on FV520B steel cylindrical specimens. Additionally, ABAQUS software was employed to predict fatigue life following the LSP process. The experimental results indicate that the surface compressive residual stresses induced by LSP inhibit both the initiation and propagation of fatigue cracks effectively, thereby prolonging the fatigue life of FV520B steel. The fatigue life of specimens at strain amplitudes of ± 0.5 %, ±0.6 %, ±0.7 %, and ± 1.0 % is improved by 132.2 %, 0.4 %, 18.0 %, and 88.8 %, respectively. A residual stress of −90 MPa is measured on the surface of the specimen and the surface hardness value increase by 48 % after LSP. The SEM results reveal that the characteristic of single crack sources for crack initiation is presented after LSP. The results of single point LSP simulation using ABAQUS demonstrate that the circumferential surface experiences a lower compressive residual stress of 30 MPa compared to a higher value of 45 MPa on the planar surface, this discrepancy arises due to rapidly decay associated with reduced rebound tensile strain on convex surfaces. A “multi-point continuous shock” simulation strategy was implemented for modeling LSP effects on the circumferential surface. The average compressive residual stress achieved was found to be 92 MPa, additionally, tensile residual stresses ranging from 8 MPa to 29 MPa were detected within secondary surfaces and inside the cylinder. Notably, discrepancies between simulated and experimental fatigue lives for LSP specimens across strain amplitudes of ± 0.5 %, ±0.6 %, ±0.7 %, and ± 1.0 % were minimal-ranging only between 10.4 % and 22.3 %.