Finite Element Simulation Of 18CrNiMo7-6 Steel After Abrasive Waterjet Peening

As a metal surface modification technology,abrasive waterjet peening(AWJP)can overcome various defects in the material manufacturing process,make the surface of workpieces form an ideal structure and residual stress distribution,and thus improve the fatigue life of workpieces.Residual stress and surface morphology are important factors that affect the fatigue life of workpieces,and generally need to be tested through experiments,all involving the removal of the surface material,resulting in high research cost,resulting in high research cost,low efficiency and complicated operation.Finite element simulation can provide an intuitive,economical and efficient research method for the process of AWJP.Therefore,in this thesis,the method of combining theoretical analysis and finite element simulation was used to further investigate the formation and coupling mechanism of residual stress field after AWJP.Under the premise of ensuring the magnitude and depth of compressive residual stress field and decreasing the surface roughness as possible,the jet process parameters were optimized.The main research contents are as follows:(1)Firstly,the formation and coupling mechanism of residual stress field after AWJP is analyzed.On this basis,the mathematical model of residual stress after AWJP is established.Next,the formation mechanism of the target surface during the sequential shot peening of abrasive waterjet is studied,and the influence laws of the shot radius,velocity and center distance on the surface morphology are obtained.(2)The single-shot finite element model of AWJP was established by using ABAQUS software.The variation of residual stress field,surface morphology and equivalent plastic strain of the target was obtained by changing the shot velocity,shot radius,impact angle and target surface.The results show that both the shot velocity and the radius affect the final strengthening effect;When the shot velocity increases,the residual compressive stress increases significantly,and the depth of the residual compressive stress layer increases;Compared with the shot velocity,the shot radius has a greater effect on the residual compressive stress depth;As the impact angle increases,the depth of the crater and the depth of the residual compressive stress layer increase significantly.When the geometrical features of the target surface are different,the reinforcement effect is groove surface > plane > cylindrical surface > spherical surface.(3)The ABAQUS finite element software was used to establish the 3D finite element model of 18crnimo7-6 strengthened by single-point fixed,single-channel sequence and multi-channel sequential shot peening of abrasive waterjet.On this basis,the residual stress field and the surface morphology of the target were studied separately.The formation and coupling mechanism of the residual stress field of the target during the sequential shot peening of abrasive waterjet were further analyzed.The mathematical model and finite element simulation results of residual stress field and surface topography are compared and analyzed.It was found that when the pits on the target surface interfere with each other,reducing the center distance of the shots can greatly reduce the surface roughness,and at the same time obtain a more uniform residual compressive stress field distribution.Increasing the shot velocity and radius is beneficial to introduce a deeper residual compressive stress layer and increase the surface roughness.