Numerical and Experimental Determination of the Effective Mechanical Characteristics of a Polymer–Grease Contact Pair

Abstract

Contact polymer-grease pairs of materials are widely used in highly loaded friction units. However, modeling the joint mechanical deformation of polymer grease significantly increases computational costs and complicates the convergence of the numerical solution. This is due to the pronounced nonlinear behavior of the materials and the significant difference in their physical and mechanical characteristics. Modeling the behavior of complex spatial configurations of structures, taking into account temperature and time factors, and investigating the behavior of structures in dynamics challenges researchers and engineers with the task of reducing computational costs for numerical experiments without loss of accuracy. Therefore, it is of high importance to form methods and approaches for describing effective characteristics, taking into account the nonlinear behavior of a polymer-grease pair of materials. Representing the design volumes of polymer grease as an equivalent medium can reduce computational costs. This paper considers the design volume, including a polymer base made of ultrahigh-molecular-weight polyethylene and a spherical recess filled with CIATIM-221 grease. The modified elastic-viscoplastic Anand model has been used to describe the behavior of materials and an equivalent medium. The model parameters have been determined based on a set of numerical experiments at various temperatures, deformation rates, and sizes of the design volume. The effective elastic and viscoplastic characteristics of the equivalent medium have been determined. An increase in temperature leads to a decrease in stiffness and resistance to viscoplastic flow. Increasing the size of the design volume helps to stabilize effective characteristics and reduce the impact of local structural heterogeneities. The proposed analytical dependencies make it possible to take into account the influence of temperature and the geometry of the design volume when determining the parameters of an equivalent medium. The developed approach can be used in finite element modeling of large structures with friction units to reduce computational costs without explicitly modeling the polymer-grease interface.