Study On Cavitation Phenomenon And Damping Characteristics Of High Quality Vehicle Shock Absorber

With the continuous development of science and technology,people have higher and higher requirements on the ride comfort,handling stability and ride comfort.Shock absorber is the most important damping element of vehicle suspension,and the performance of shock absorber is very important,which directly affects the comprehensive performance of vehicles.However,there are still some difficult technical problems in the production of shock absorbers in our country,such as abnormal noise,overheat and out-of-control damping,which seriously reduce the reliability and safety of shock absorbers and lead to the decline in the quality of shock absorbers.Therefore,it is necessary to analyze and study the cavitation phenomenon and damping characteristics that affect the quality of vehicle shock absorber.This paper is supported by the Key Research Program of Jiangxi Province(20171BBE50039).First of all,based on the specific structure of the double cylinder hydraulic shock absorber,the working principle of the double cylinder hydraulic shock absorber is analyzed and studied.Then,the CFD numerical method of the simulation calculation of the vehicle shock absorber is systematically analyzed and studied,and the mathematical model of internal structural parameters design of the recovery valve is established according to the actual work situation of vehicle shock absorber.Secondly,in order to solve the problem of abnormal noise of vehicle shock absorber,the finite element fluid simulation model of vehicle shock absorber recovery valve was established.In FLUENT software,the cavitation phenomenon in the working process of vehicle shock absorber recovery valve was simulated and studied,and the test was verified.The results show that with the increase of the shock absorber working speed,the cavitation phenomenon of the recovery valve is generated near the recovery valve plate and the piston hole first,then the cavitation is distributed along the upper edge of the recovery valve plate,and finally the cavitation is all around the recovery valve plate,and it tends to spread to the lower cavity of the shock absorber;using oil with low kinematic viscosity and increasing piston rod diameter can effectively inhibit the cavitation phenomenon of vehicle shock absorber.Thirdly,in order to solve the problem of overheating of vehicle shock absorber,the internal heat generation mechanism of vehicle shock absorber recovery valve was simulated and analyzed in FLUENT software.The results show that with the increase of the working speed of the shock absorber,the internal temperature of the shock absorber increases gradually,and the temperature field changes from uniform distribution to disorderly distribution;with the extension of time,the oil temperature inside the shock absorber increases and tends to the thermal equilibrium state;using low density and high thermal conductivity of shock absorber oil can effectively inhibit the overheating of vehicle shock absorber.Finally,in order to solve the problem of out of control damping of vehicle shock absorbers,the two-way fluid structure coupling simulation analysis of the damping characteristics of shock absorbers is carried out in the workbench software.The results show that when the shock absorber works at a low speed,the pressure field distribution is even,the damping force inside the recovery valve is small,and the area of multi-groove of the superposition valve is the biggest factor affecting the damping characteristics of the shock absorber;when reaching the speed point of valve opening,the pressure distribution inside the recovery valve suddenly becomes disorderly,and the pressure field fluctuates greatly,at this point,the damping force inside the recovery valve suddenly increases,but the damping force is moderate,and the displacement and velocity of the superposed valve plate will change by leaps and bounds at the same time;when working at high speed,the pressure field inside the shock absorber recovery valve fluctuates obviously,the damping force reaches the maximum,and the diameter of piston hole is the biggest factor that affects the damping characteristic;the pressure at the outer radius of the fluid-solid coupling surface is small,while the pressure at the inner radius is large,and the pressure field fluctuation of the fluid-solid coupling surface is the largest at the outlet of the piston hole,so the damping force is the largest at the outlet of the piston hole of the fluid-solid coupling surface;the maximum stress on the superposed valve plate occurs at the inner radius,but the maximum deformation area is near the piston hole.