Study On Hydro-pneumatic Spring Damping Structure

Hydro-pneumatic spring are widely used in large-tonnage dump trucks and heavyoff-road vehicles for its excellent non-linear characteristics. With the development of thetimes, China’s automobile industry has also achieved considerable progress, and the currentperformance of the car has been unable to meet the increasing need of people for ridecomfort and handling stability. The performance of the suspension will directly affect ridecomfort and handling stability of the vehicle. The hydro-pneumatic spring is the corecomponent of hydro-pneumatic suspension, so try to increase the characteristics of thespring stiffness and damping structure is very important.The traditional optimization methods for the characteristics of damping structure ofhydro-pneumatic spring are constantly revising design parameters by a large number ofexperiments, which is time-consuming and costly. Benefit from the rapid development ofcomputer technology, it has become possible for us to do dynamic simulation analysis forthe characteristics of the hydro-pneumatic spring damping structure using the finite elementmethod. We can optimize the characteristics of damping structure at the beginning design ofthe hydro-pneumatic spring, which can greatly shorten the design cycle and reduce thecosts. We completed the fluid-structure coupling analysis for the characteristics of thehydro-pneumatic spring damping structure byANSYS Workbench in this thesis.Analysis of the characteristics of the hydro-pneumatic spring damping elements werecarried out and the theory of fluid-structure interaction was introduced. Firstly, the physicalcharacteristics of the fluid medium and Newton ’s law of friction were analyzed.According to the theory of fluid mechanics, the fluid dynamics equations and the orificeflow equation were obtained, the large deflection of valves was calculated based on theknowledge of elasticity. Then the basic theory of fluid-solid coupling was introduced,providing theoretical foundation for the subsequent analysis.Mathematical model of the hydro-pneumatic spring was established. The work of thehydro-pneumatic spring was analyzed by the spring structure, and the damping forceformulas of the recovery valve and compression valve were deduced. The solid model of hydro-pneumatic spring was established and the simulation offluid-structure coupling was carried out. The professional3D modeling software CATIAwas used to establish the geometry models of the damper valves and oil of thehydro-pneumatic spring. The models were symmetrically split in Design Modeler moduleof ANSYS Workbench platform after corresponding simplified. The finite element model ofdamping structure was obtained after meshing by HyperMesh, the professional meshingtool. Then the finite element model was imported into ANSYS Workbench platform. Thecalculation of fluid-solid coupling simulation was carried out after a series of settings. Thepressure contours and the velocity streamlines were obtained through analyzing the resultsof calculation.The simulation results were verified through bench test. The speed characteristic andindicator diagram of hydro-pneumatic spring damping structure were obtained byprocessing the bench experiment data. The process of modeling, the method of simulationand the results of solving were proved correct after comparing the results of simulation andexperiment.