Effect Of Laser Shock Peening On Aviation Aluminum Alloy Service Capability

Laser Shock Peening(LSP)is a common surface treatment technology,which uses highpower density,short-pulse laser to act on the energy layer of the material surface to heat it up to generate a plasma shock wave,the plasma shock wave imposes force on the material.It can bring residual stress field and gradient structure to the surface of the material,so that the material becomes a gradient nano-grain structure material.The existing grain boundaries and residual stress field will hinder the movement of dislocations and promote the improvement of material properties.In this paper,the vibration response characteristics of laser shock peening 2024-T4 aluminum alloy and the uniaxial tensile and fatigue properties of laser shock peening 7075-T7351 aluminum alloy were studied respectively.Through micro-characterization,macromechanical experiments and finite element simulation methods,the improvement effect of laser shock peening technology on the mechanical properties of materials was explored.Finally,the high-cycle fatigue life of materials before and after laser shock peening was predicted.The main research contents of this paper are:(1)The vibration response characteristics of laser shock peening aviation aluminum alloy were experimented and simulated.The influence of laser shock peening on the frequency and amplitude ratio of the target mode shape was explored,and the laser shock peening parameters with the best effect on improving the vibration characteristics were found.(2)The XRD test experiment of laser shock peening aviation aluminum alloy was carried out.According to the XRD pattern,the changes of grain size and dislocation density along the impact depth direction were given.The grain size gradually increased along the depth direction.The dislocation density gradually decreased along the depth direction.In addition,the existed residual stress field for the laser shock peening aviation aluminum alloy was measured,the distribution curve of the residual compressive stress field along the impact depth was drawn,and a finite element model was established to simulate the residual stress field distribution after impacting the material with different laser shock peening parameters.Provide parameter support for subsequent simulation model.(3)A series of uniaxial tensile,low-cycle and high-frequency fatigue macro-mechanical experiments were carried out for the laser shock peening aviation aluminum alloy to study the effect of laser shock peening on the mechanical properties of the material.At the same time,relying on CMSG theory to establish finite element model,in which the gradient structure and the initial residual stress field is considered.The uniaxial tensile and cyclic mechanical responses of the material before and after laser shock peening were calculated and compared with the experiment results.It was found that laser shock peening brought significant improvement to the uniaxial tensile properties and fatigue life of the material.(4)Based on the established finite element model,the high-cycle fatigue life of the aviation aluminum alloy was predicted.The results show that both the predicted fatigue life and fatigue life from experiment of each stress level were distributed within the three times error band or near the error band.In addition,the predicted fatigue life before and after adding the residual stress field were calculated respectively.It was shown when the residual stress was not considered,the fatigue life predicted on each stress level decreased significantly.When the stress level was low,the residual stress played a more important role in improving the fatigue life.