Non-linear Characteristic Simulation of Hydraulic Shock Absorbers Considering the Contact of Valves

Abstract

This paper presents a detailed model of a hydraulic shock absorber. The detailed structure includes in the model, such as the deflection of valve which deforms in the oil, the contact between the superposition valves et al. The FEM is used to solve the valve deflection problem. The difference between the FEM result and formula result which is acquired by Mechanical Design Handbook is analyzed. The detailed Mathematical model is simulated by MATLAB and the simulation results fit the experiment data very well. This shows that the model can be used to forecast the performance of hydraulic shock absorber when design. experimental test. This model is simple and needs less computation, therefore, it is often used in the vehicle system dynamics and vibration simulation. However this model can not reflect the internal structure of the damper in detail, simulate its internal working process precisely and imitate the direct influence in its performance due to the change of its internal construction. The other type is the detailed physical model which is constructed based on the internal structure of the damper(5). The knowledge about hydromechanics is used to set up the complex coupling dynamic equations that can express the internal structure of HSA. The pressure of each chamber is determined during its working progress. Some scholars utilize the maximum deflection factor and calculation formula in the mechanical design handbook to solve valve deformation during the damper working. However, the mentioned formula could only calculate the maximum deflection of the valve at the external diameter. For the low speed case, calculation results from this method is close to experimental results(6). Some other scholars employ elasticity theory to study above problem. They formulate a differential equation of the valve deformation and give a very complex general solution(6). Although the results obtained from HSA model constructed by this way matches with the experimental results very well , this method may not be able to apply to the simulation of damper performance due to its complexity.