Evaluation of effectiveness of pneumatic suspensions: Application to liquid sloshing problems

Abstract

In this investigation, a pneumatic suspension model with orifice damping is developed and used to evaluate the performance of the air suspension in comparison with the coil-spring suspension in railroad and highway transportation systems. In railcars, air springs are used to isolate the car from vibrations caused by track irregularities, while in highway trucks, air springs are often used in their rear suspensions to allow adjusting the suspension characteristics depending on the load conditions. The air spring formulation is validated by comparing the dynamic stiffness with the stiffness of other models reported in the literature. Different motion scenarios are considered to quantify effectiveness of the air spring in liquid sloshing problems. To capture the large displacements experienced by the liquid, the finite element (FE) absolute nodal coordinate formulation (ANCF) is used with a penalty approach to model the fluid/tank contact forces. In the railroad vehicle models, the wheel/rail contact is modelled using a nonlinear three-dimensional elastic contact formulation that accounts for the creep forces and spin moment, while in the highway-truck model, the wheel/ground interaction forces are modeled using a discrete-element tire model. In addition to comparing with coil springs, the paper discusses the differences between the pneumatic and active suspensions. The simulation results show that using air springs reduces the railcar mean vertical acceleration, maximum roll angle, and variations in the wheel/rail contact forces. The mean vertical acceleration of the truck tank is found to be lower when air springs are used, resulting in a reduction of the force exerted by the fluid on the tank walls.