Direct numerical simulation of mixed lubrication in elastohydrodynamic systems

In the field of hydraulics, reciprocating rod and piston seals are crucial for the performance of cylinders and actuators. With respect to energy efficiency, leakage as well as product lifetime, numerical design tools play an important role in the design process of these seals. In recent decades, various numerical models for the prediction of tribological characteristics of reciprocating seals have been proposed. However, these models are often time-consuming to set up and come with long computation times. In recent years, advances in soft- and hardware have lead to the trend to solve complex elastohydrodynamic systems undergoing mixed lubrication within a single multiphysics platform. By coupling solid mechanics, surface mechanics and fluid mechanics using the direct method, mixed lubrication in elastohydrodynamic systems has been successfully modeled for axisymmetric O-rings. Building on this, the presented work explores a two-component sealing system using the COMSOL® Multiphysics platform, enabling comprehensive coupling of solid, surface, and fluid mechanics. The numerical model's validation involves a test rig measuring friction from reciprocating seals, 3D surface texture characterization of the sealing lip, and an application-oriented test apparatus to determine the coefficient of friction for the rod-seal contact pair. This study aims to validate the direct method for a multi-part elastohydrodynamic system, emphasizing experimental validation to assess the accuracy of mixed lubrication models.