A comprehensive analysis and improvement of classical non-conformal contact force models for revolute joints with clearance

Revolute joints are widely used in various engineering fields such as deployable space structures and robotics. Currently, various theoretical models have been applied to evaluate the normal contact force of the revolute joints; however, the results obtained by these models often exhibit significant discrepancies, and there is a lack of explanation for the reasons behind these discrepancies. This study explores the underlying theories of three classical non-conformal contact force models for revolute joints, namely the ESDU-78035 model, the Radzimovsky model, and the Dubowsky-Freudenstein model. The theoretical differences among these classical models are analyzed, and their deficiencies are discovered, and then an improved non-conformal normal contact force model is presented. To validate the accuracy of the presented model, three-dimensional refined finite element models employing surface-to-surface contact elements are constructed to simulate the normal contact of the revolute joint with different clearance sizes and different contact lengths. A comprehensive comparison is carried out between the semi-contact-width, contact pressure, and load-deformation curves obtained from the theoretical models and the finite element model. The results indicate that the presented contact force model outperforms the three classical contact force models in terms of accuracy. The differences between the ideal contact model and the real revolute joint are also investigated, and a sub-model modeling method is presented for the real revolute joint based on the ideal contact force model.