Study On Plastic Metal Surface Strengthening Based On High Pressure Water Jet

The development of upmarket equipment industry puts forward higher requirements for surface strengthening technology.As a new technology of wet green shot peening,high pressure water jet has many advantages,such as high efficiency,low cost,high flexibility,good quality,no pollution and so on.This paper works on the surface strengthening process optimization of high pressure water jet for plastic metal materials.The impact characteristics of pure water jet and abrasive water jet are compared and analyzed,the mechanism of jet strengthening is studied,the influence of process parameters on strengthening quality is analyzed,the prediction model of surface strengthening quality of high-pressure water jet is constructed,on this basis,the process parameters are optimized,and the feasibility of indirect strengthening of abrasive water jet is explored.The main research contents are as follows:(1)Study on the basic theory and surface strengthening mechanism of high pressure water jet.Based on Mises yield theory,a mechanical model of jet strengthening is established,and the boundary conditions of critical crack damage and critical plastic deformation are given.(2)Numerical simulation of flow field inside and outside the nozzle.Based on the computational fluid dynamics,a simulation model of the flow field inside and outside the nozzle is built,and the velocity field and pressure field distribution law under different jet pressure and target distance are analyzed.The velocity attenuation and interface impact of the water phase in the pure water jet are analyzed.The velocity attenuation,velocity slip and interface impact of the abrasive phase and water phase in the abrasive water jet are studied,which confirms the energy distribution law of the jet structure and clarifies it Abrasive phase is the main energy carrier of abrasive water jet.(3)The influence of process parameters on the surface quality of jet strengthening.The effects of jet pressure,target distance,feed rate and traverse speed on the surface roughness and hardness of workpieces strengthened by jet are analyzed.The parameter range is optimized.The orthogonal test is carried out to analyze the major and minor effects of process parameters on strengthening quality.The prediction models of surface strengthening quality of pure water jet and abrasive water jet are constructed respectively.The results show that the surface roughness and hardness increase with the jet energy.The results show that the surface roughness and hardness increase with the increase of pressure,and decrease with the increase of target distance,feed rate and traverse speed.(4)Study on the optimization of high pressure water jet surface strengthening technology.Based on the regression prediction model of surface strengthening quality,a multi-objective optimization model for surface roughness and hardness is established;based on the multiobjective genetic algorithm,the Pareto optimal solution set of jet strengthening process parameters is solved;the indirect strengthening method of abrasive water jet is proposed,and the feasibility of the method is verified by experiments,and the advantages and disadvantages of different water jet surface strengthening processes are compared and analyzed.