Numerical Simulation And Experiment On Shot Peening With Paving Thin Rubber Layer

Shot peening is a deformation process.When the projectile repeatedly impacts the surface of metal parts,the metal surface will produce high strength residual pressure,which is of great significance to improve the mechanical properties of metal parts.However,the shot peening process also improves the surface roughness of the workpiece and causes the initiation of surface microcracks.Previous studies have shown that the impact friction of pellets on the workpiece surface at high speed is the main reason.Starting from the impact characteristics of shot peening particles,this paper proposes a method of adding thin rubber layer on the surface of the workpiece.Through the large deformation characteristics of rubber,the direct contact friction between shot peening particles and the surface of the workpiece is blocked,and the goal of improving shot peening quality is achieved.The finite element models of single shot and multi shot were established respectively to explore the effectiveness of shot peening process for thin rubber layer.The velocity variation trend of shot peening on workpiece,the stress and strain state of rubber layer and workpiece surface and the indentation state were studied.The results show that the thin rubber layer shot peening can continuously stress the workpiece,and reduce the protrusions on both sides of the pits caused by the impact of shots on the workpiece,thereby improving the surface roughness of the workpiece and improving the surface quality of the workpiece.In the simulation model of single shot(diameter of shot is 1mm),through the simulation analysis of different rubber thickness,when the rubber thickness is 0.2mm,the residual compressive stress is reduced from 391 MPa to 373 MPa,the loss is 4.6%.At the same time,the single shot pit is reduced from 56.2μm to 35.4μm,the loss is 37%.The surface roughness of the workpiece is reduced when the residual compressive stress is maintained.For the finite element simulation of multi-shot(0.36 mm in diameter),the experimental study on the surface stress state and the optimization effect of the surface roughness of the workpiece after the multi-shot impacts the workpiece under the condition of satisfying the coverage requirement shows that the relative error between the simulation value and the experimental value is 12.8%,which verifies the correctness and effectiveness of the simulation of laminated rubber.Previous studies have shown that the quality of shot peening is closely related to the motion characteristics of shot peening.In order to explore the motion characteristics of shot peening,particle image velocimetry based on high-speed camera was used to study the motion characteristics of shot peening in three situations: free shot peening,traditional shot peening and laminated rubber shot peening.The results show that the maximum shot speed from the nozzle is 10.5% lower than the theoretical shot speed,and the speed trend of the central shot is characterized by increasing speed,reaching the maximum value and decreasing speed.Compared with the pellets in the center path,the velocity of the pellets at the edge of the beam will decrease significantly,but it still follows the velocity trend of the center pellets.Shot peening can not only improve the mechanical properties of the workpiece,but also affect its surface corrosion characteristics.Based on the salt spray test method,the corrosion evolution characteristics of the original sample,the shot peening sample,the laminated rubber shot peening sample and the corresponding three samples after electroplating under salt spray conditions were studied.The results showed that under the same corrosion conditions,the mass loss of the original sample,the shot peening sample and the laminated rubber shot peening sample showed a decreasing trend,and the surface quality loss of the laminated rubber shot peening workpiece was reduced by 16.05% and7.35% compared with the original sample and the shot peening sample,respectively.The coupling of shot peening and electroplating can effectively improve the rust and pitting corrosion of the workpiece in salt fog environment,while shot peening,electroplating and thin rubber layer can further improve the surface roughness of the workpiece.There are 61 pictures,5 tables and 81 references.