Frictional Contact Finite Element Analysis of Pneumatic Cylinders

Abstract

Friction is present in most mechanical systems. The aim of this paper is to analyse friction between a pneumatic cylinder and its piston seal using the finite element method (FEM). The high-fidelity numerical model used real geometry and material characteristics of a double acting pneumatic cylinder. The simulations required fine tuning: the piston seal was created with a hyperelastic, nearly incompressible material model utilizing mixed u-p elements. Three friction characteristics were analysed with slow velocity motion of the piston: Coulomb, an extended Coulomb and the Benson-Hallquist model. The result of the Coulomb model has given a constant friction force after an oscillation at first. The extended Coulomb friction model is used to show the effect of cohesion between two surfaces. After that, the Benson-Hallquist model was simulated by FE and then experimental and FE results were compared. As a result, an exponentially decreasing friction force was obtained. It was shown that the friction behaviors can be simulated with FE and this method will allow studying the effects of different types of piston seal and cylinder barrel on the friction force.