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In the single-sided design of a multidisk clutch or brake, each disk is composed of a steel core with a single layer of friction material bonded to one side. Each disk in the pack faces in the same direction so that the rubbing surface of friction material slides against the bare metal surface of the adjacent disk. This design has been known for years and can be considered an alternative to the much more common double-sided design. In the paper, thermomechanical effects in the single-sided clutch are studied. Finite element simulation shows characteristic pattern of thermal deformations of friction disks, peculiar to that design. The pattern is accompanied by non-uniform contact pressure at some sliding interfaces and high thermal stresses in the disks. The stresses may exceed the yield limit and this results in the known permanent conical distortions of the disks. The theoretical predictions were confirmed in experimental tests performed on inertia-type test stand.

In one of the fatigue tests for wet friction materials, “bump test”, an inertia-type rig equipped with a multi-disk assembly is used. One of the steel disks in the assembly has radial bumps for the purpose of creating high local contact pressure and high temperature. Due to the severe contact conditions, a comparative testing for different friction materials can be conducted within a relatively small number of cycles. In the paper, a design of a “bump” assembly used for automotive wet friction materials is described. Based on both experimental tests and advanced contact modeling, non-uniform contact pressure generated by the bumps and resulting temperature are estimated. The computational model is used then to study the influence of the modulus of elasticity of the friction material and reaction plate thickness on the contact conditions. The bump fatigue tests lead ultimately to material failure.

Thermal distortions of friction disks caused by frictional heating modify pressure distribution on friction surfaces. Pressure distribution, in turn, determines distribution of generated frictional heat. These interdependencies create a complex thermoelastic system that, under some conditions, may become unstable and may lead to severe pressure concentrations with very high local temperature and stress. The phenomenon is responsible for many common thermal failure modes of friction elements and is known as frictionally excited thermoelastic instability (TEI). In the paper, one of the cases of TEI is investigated theoretically and experimentally. The study involves a two-disk structure with one fiction disk and one matching steel disk that have one friction interface. An unsteady heat conduction problem and an elastic contact problem are modeled as axisymmetric ones and are solved using the finite element method.