Computational Method of Static and Dynamic Mechanical Properties of a Rolling Lobe Air Spring

To investigate the static and dynamic mechanical properties of air springs and their influencing factors, two models were established in this paper to calculate the static and dynamic mechanical properties of air springs, including a simulation model based on the finite element method and a mathematical calculation model based on thermodynamic theory. First, a performance calculation model for rolling lobe air springs with aluminum tubes was established, which considered the thickness of the bellow and the impact of the inflation and assembly process on the state of the bellow. The static and dynamic mechanical properties of air springs were calculated using this model, including static load-bearing capacity and static/dynamic stiffness. The calculation results showed that both the static characteristics of the air spring under isothermal conditions and the dynamic characteristics under adiabatic conditions were able to be calculated accurately. However, the changes in dynamic stiffness and the hysteresis phenomena caused by heat exchange during the polytropic process of the air spring are unable to be simulated by the finite element model. A mathematical calculation model was then established to analyze the mechanical properties of air spring during polytropic process. Some factors , such as heat transfer, external work and mass exchange, which cause changes in energy and temperature, were considered in the model. The dynamic characteristics of the air spring under different excited amplitudes and excited frequency were calculated using this model. The comparison of the calculation and experimental results showed that the dynamic stiffness and hysteresis characteristics of air springs across various frequencies were able to be calculated effectively by the proposed model, and the maximum relative error of dynamic stiffness and hysteresis force were less than 5%.The influence of volume, pressure, and heat exchange performance on the dynamic characteristics of the air spring were analyzed using the model. The modeling and analysis methods in this article can predict the static and dynamic mechanical properties of air springs and analyze the influence of relevant structural parameters, providing guidance and reference for designing the rolling lobe air springs.