Parametrized Finite Element Analysis Of Tribological Instabilities On Polymer-Metal Sliding Contacts

Frictional instabilities, commonly named as “stick-slip”, constitute a challenge when referring to tribological desip ofpolymer components in a wide range of industrial applications. Several systems such as hydraulic gearshifts, elevator sliders and many other hydraulic and pneumatic actuation systems are influenced by this phenomenon commonly associated to system control problems (system vibrations & noise) and to the reduction of the senrice life of polymeric components. From a macroscopic point of view, the “stick-slip” phenomenon consists on the sudden and successive chance of the state of movement between two slidine su~facesi n contact lubricated or not from “static” to “sliding”. With the objective of developing a numerical tool to analyse this phenomenon, the polymer-metal sliding system can be mathematically simplified by a mass-spring system over a moving surface and im~lemented into a ~arametnredm odel simulated with a commercial FE software. The explanation of the “stick-slip” through this simplification is that, when the force of the spring equals the friction force the relative movement stws, and due to the decrease of the friction coefficient from static to kinetic, and the negative friction-velocity slope, the mass suffers an acceleration in the direction con- to the surface velocity. The methodology based on the parametrization of the FE simulations allows to study the influence of several system variables such the frictional force evolution, the mass of the system, the spring stiffness, system damping, sliding speed. .. with a reasonable computational cost. All these system variables corresponding to the simplified mass-spring model are connected to the real system in the way that an analysis or proposed modification on any of them can be directly translated into effective modifications of the real system to prevent or to minimise “stick-slip” events. Once the set of parametrized FE simulations are evaluated and experimentally validated, an approximated map of correlations can be obtained by means of statistical methods with the final purpose of getting a v h a l prototyping tool to ease desip process and to predict tnbological instabilities on polymeric components.