Effect of local laser heating on fatigue crack propagation rate of AA2524 thin plate

Abstract

To extend the operational lifespan of the AA2524 aircraft panel, the surface of the AA2524 specimen was locally heated by laser. The specimen’s microhardness distribution and surface residual stress (RS) were tested, as was its fatigue crack growth rate (FCGR). The fatigue fractography of specimen was also observed. The FCGR of specimen after laser heating was predicted by the weight function method (WFM). The consequences indicate that when the laser power is lower than 900 W, the hardness of the heating zone on the surface of the specimen decreases by no more than 10 HV0.5. Compared to the base material (BM) specimen, transverse heating specimen creates a maximum compressive residual stress (CRS) of 32 MPa along the crack extension line. This can effectively stop the crack propagation. When laser power with the transverse heating is 900 W, the crack propagation suppression effect is optimal. The fatigue life of heated specimen is increased by 108.5 % compared to the BM specimen under a constant amplitude load with the maximum load of 2600 N and R of 0.1, and the fatigue life of heated specimen is increased by 46.4 % under a constant amplitude load with the maximum load of 3300 N and R of 0.1. The spacing among 6 adjacent striations of specimen after transverse heating is shortened from 2.79 μm to 0.88 μm compared with the BM specimen. The Walker model, which is based on the WFM, has high accuracy in predicting FCGR of specimen after laser heating under various load conditions. It is evident that local laser heating technology can extend the service life of aviation aluminum alloy panels.