Effect of Stress Wave Propagation on Surface Stress Relaxation in 7050 Aluminum Panel Shocked by a Nanosecond Laser

Integral panel is an important structure to reduce aircraft weight. Nanosecond laser beams can be used for the forming and surface modification in panels. To explore the propagation of laser-induced stress waves and their influence on surface stress relaxation, a simulation model is used to capture the propagation process of stress waves. The results show that the stress wave first decays rapidly, and then the attenuation rate decreases gradually. In the initial propagation stage, the attenuation of the stress wave can be fitted by σx=Ee-kx; then, after propagating a certain distance, the stress wave amplitude is more suitable to σx= Ex-k. During the propagation processing, the stress wave is reflected on the shocked and back surface. A tensile stress wave is formed by the reflection of the incident compressive stress wave, and the value of the stress wave is improved. The stress wave has a great influence on the residual stress distribution in 1mm thin panels. When the stress wave is reflected on the back surface, a stress is induced into the surface. When the stress wave is reflected by the shocked surface, the stress on the surface is relaxed because the incident wave is a tensile wave. Therefore, when a nanosecond laser is used in thin panels, the shock wave has an important influence on the stress distribution, which needs to be considered in engineering applications.