Abstract: In this paper,first,a semi-active hydraulic damping strut is made equivalent to a two-DOF model of mass and spring,and a dynamic stiffness expression is derived.Next,a nonlinear rubber bushing model based on the linear elasticity,the fractional derivative and the friction model,is constructed,and the Maxwell model is adopted to describe the stiffness of a general damper.Then,the parameters in the dynamic stiffness model of the rubber bushing and the general damper are identified by means of the least square method.Finally,the dynamic stiffness of the semi-active hydraulic damping strut under power-on conditions is compared with that under power-off condition through experiments and simulations,and the influence of the equivalent spring stiffness,the damping constant and the rubber bushing stiffness on the dynamic stiffness and damping capacity of the semi-active hydraulic damping strut is analyzed.The results show that (1) the dynamic stiffness of the semi-active hydraulic damping strut increases with the increase of the rubber bushing stiffness,the equivalent spring stiffness and the damping constant; (2) increasing the damping constant helps to improve the dynamic stiffness of the semi-active hydraulic damping strut at low frequencies,and decreasing the rubber bushing stiffness and the equivalent spring stiffness helps to reduce the dynamic stiffness of the semi-active hydraulic damping strut at high frequencies; (3) the ru- bber bushing stiffness has a smaller effect on the damping capacity of the semi-active hydraulic damping strut; and (4) the smaller the equivalent spring stiffness and the damping constant are,the better the damping capacity of the semi-active hydraulic damping strut will be.

Key words: semi-active hydraulic damping strut, dynamic stiffness, damping capacity