Calculation of the elastic characteristics of the pneumohydraulic shock absorber of a tracked vehicle

Tracked vehiclesused in military, construction, and industry are subjected to significant dynamic loads that challenge conventional suspension systems. Pneumohydraulic shock absorbers (PHSAs) provide an advanced solution by integrating both elastic and damping functions into a single unit. Such integration results in high specific energy capacity and a non-linear, progressive elastic characteristic, which is critical for absorbing large impacts without bottoming out while ensuring ride comfort under normal conditions. The present paper is dedicated to modeling and analyzing the crucial elastic characteristic. A mathematical model describing the operation of a PHSA is presented. The model utilized a thermodynamic (zero-dimensional, lumped-parameter) approach to simulate the pressure interactions in the hydraulic cylinder and - pneumatic accumulator. The simplified approach based on fundamental equations of piston motion, fluid flow through a throttle orifice and polytropic gas compression, allowed performing a computationally efficient analysis. The model assumed an incompressible hydraulic fluid and ideal gas behavior, neglecting frictional forces for clarity. Using the model, numerical simulations were conducted to determine the dynamic characteristics of the piston displacement under varying forces on the rod. The study also investigated the influence of the throttle orifice size on the system dynamic response and the time required to reach a static equilibrium was calculated. The calculations of the PHSA's static load were performed and analyzed. A key finding of the present work is a strong correlation between the simulation results and available experimental data, which validates the model predictive capability. The calculations successfully replicate the progressive nature of the PHSA's elastic curve. The developed model serves as a valuable tool for the preliminary design and optimization of PHSAs for heavy-duty tracked vehicles.