Abstract
The current high standards of road safety and the responsibilities of vehicle manufacturers to ensure a good quality product have brought about the need for manufacturers of component parts to take new steps to test their products at the production stage for consistency of performance.
This paper refers to earlier types of friction testing machines and describes the design, construction and operation of a machine for testing friction materials both as a functional quality control instrument, and to categorize materials into performance groups.
The machine has been operated on the basis of intermittent cyclic application, and covers a range of rubbing speeds and pressures which should suffice for the majority of automotive conditions.
By ensuring that the ratio of surface area of specimen to thermal capacity of heat sink is of the same order of magnitude as experienced in practical conditions, the test machine simulates not only energy dissipation rates, but also rate of rise of temperature. It is considered by the authors that this factor is of first importance in achieving good correlation with service performance and takes precedence over other design features of the machine including the selection of sample area and shape.
A number of these machines have now been in operation for several years and a great deal of experience gained in their use. The results obtained are in broad agreement with those obtained on vehicles in service and the machines are now used in intensive quality control.
Many European countries and America have issued acceptance specifications which have no common basis, and this paper is presented in the hope that a discussion of its design features will lead to the evolution of a widely acceptable uniform specification.
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