Simulation Research Of Influence Of Laser Shock Peening Parameters On Residual Stress Distribution In Aluminium Alloy

The lightweight of automotive makes the application of aluminum alloys more and more widely in automobiles.Key components made of aluminum alloys may have problems such as insufficient strength and poor fatigue performance.Laser shock peening(LSP)is a new type of metal material strengthening technology.LSP has features such as ultra-high pressure,ultra-short time and ultra-high strain rate.It can generate high residual compressive stress along the depth in the workpieces with complex surfaces to improve the mechanical properties of aluminum alloys and effectively improve the performance of aluminum alloy parts.In this paper,the influences of laser parameters and specimen shape on the residual stress distribution in 5052-H32 aluminum alloy is investigated by using finite element simulation methods.The main research work and conclusions of this paper are as follows:(1)A finite element model of LSP 5052-H32 aluminum alloy was established using a finite element software ABAQUS.The simulation results showed that the compressive residual stress amplitude and the depth of compressive residual stress layer of aluminum alloy increased with the increase of laser energy but the coverage area of the compressive residual stress was relatively reduced.As the energy increased to a certain value,the maximum compressive residual stress on the surface of the aluminum alloy decreased,and the residual stress distribution becomes uneven.When the peak pressure of laser pulse induced shock wave was constant,the compressive residual stress amplitude and the depth of the compressive residual stress layer of the aluminum alloy specimen increased with laser pulse width;when the laser pulse energy was constant,the surface compressive residual stress amplitude and the compressive residual stress layer depth of the aluminum alloy specimen also increased with the increase of the pulse width.(2)The finite element model was used to investigate the influence of the number of laser impacts and the laser energy loading method on the residual stress distribution in the 5052-H32 aluminum alloy specimens.The simulation results showed that increasing the number of laser impacts could increase the compressive residual stress amplitude on the specimen surface and made the residual stress distribution more uniform,but the increase in the number of laser impacts cannot effectively deepen the compressive residual stress layer.For 5052-H32 aluminum alloy,the compressive residual stress distribution induced by LSP with a peak pressure of 1.15 GPa followed by 1.65 GPa was better than that of two laser impacts by 1.65 GPa,which indicates that the compressive residual stress in the aluminum alloy can be optimized through variable energy loading.(3)The finite element simulation model was used to study the effect of specimen thickness on the residual stress distribution.The results showed that the specimen thickness had little effect on the maximum compressive residual stress on the surface,but the coverage area was significantly reduced with the decrease in thickness.Moreover,the depth of compressive residual stress layer did not change with the thickness of the specimens,but the aluminum alloy plate with a thickness of 1 mm showed a large compressive residual stress on the back surface after LSP.(4)The distribution of residual stress in the specimens with different surface shapes after LSP was studied.The results showed that the compressive residual stress on the surface of the concave specimen is greater than that of the convex specimen.The compressive residual stress of the concave specimen increased with the decrease of the curvature radius while the compressive residual stress in the convex specimen decreased with decreasing radius of curvature.For the convex and concave specimens,when the radial thickness of the specimen was 3mm and 2mm,the distribution of the residual stress was basically the same in the surface and depth direction.When the thickness of the specimen was 1mm,the maximum compressive residual stress on the surface was much less than the other two thickness.For 1mm plate specimens,compressive residual stress could be observed on the back side of the LSP surface when the shock wave peak pressure was 1.15 GPa,while the back surfaces of the convex and concave specimens were in unstressed status.