Modeling And Simulation On The Hydraulic Shock Absorber’s Thermal Characteristics Of A Passenger Car

Hydraulic shock absorber’s working principle is that the damping force produced bythrottling valve is used to attenuate the vehicle vibration. The work did by damping forcetransform the vibration energy into heat. A part of the heat is absorbed by the shockabsorber which causes the fluid temperature, and another part is emitted to the atmosphereby means of heat exchange because the temperature difference between the environmentand the damper. The absorption of heat and dissipation is a dynamic cycle of thesynchronization process, which will eventually be in a thermal equilibrium state. In thisprocess, the rise of temperature will cause change of the fluid viscosity, then leads to thechange of damping force, which affects the damping characteristics of the shock absorber.Further, when the oil temperature reaches a certain level, the seal’s aging will accelerate andresult in failure. Therefore, the heat issue of shock absorber needs attention.Combined with the project "The liquid-solid-thermal coupling model and simulationresearch of the hydraulic shock absorber" which is in cooperation with the center of ChinaFAW Group Corporation, the thermodynamic model of twin tube hydraulic shock absorberis studied in the thesis. The main theories include fluid mechanics, heat transfer, engineeringthermodynamics, and so on. The concrete contents are summarized as follows:First of all, through the separation of the shock absorber entity structure and the read ofreferences, I have understood the structure, working principle and the heat transfer processof the shock absorber. On the basis of the theory of fluid mechanics, heat transfer,engineering thermodynamics, the mathematical model of the thermodynamic model of theshock absorber was built. Then the simulation model of this shock absorber based on thesoftware AMESim was built. By comparing the experimental data and simulation data, wecan validate the correctness of the model. After that, find several key parameters and studytheir influence on the thermal equilibrium temperature of shock absorber, which can provide reference for the design of shock absorber. These parameters can be divided into threecategories: the method of loading (sinusoidal excitation amplitude, frequency), thestructural parameters (rod diameter, cylinder length, outer tube diameter, the diameter of thevalve, diameter of piston hole, piston gap, pretightening force of compression valve),attribute parameters of hydraulic oil (fluid density, thermal conductivity), the externalenvironment (ambient temperature, wind speed).Finally, get the time domain model of roadbased on white noise filtering method, establish its simulation model based on MATLAB/Simulink, and thus export the curve of road roughness, after that, create the mathematicalmodel of1/4vehicle suspension system, then establish the simulation model based onAMESim, then put the curve of road roughness into the AMESim as input to analyze thethermal characteristics of shock absorber on different operating conditions.Currently, the research on shock absorber home and abroad mainly focus on themechanical properties, on the contrary little research on the heat. Through the establishmentof simulation model on the heat-liquid-solid coupling of shock absorber, summarizes therule about how the key parameters affect its equilibrium temperature, finally analyzes anddevelops the thermal characteristics on the different driving conditions, which can provide atheoretical basis on the design of the shock absorber.