Measurement of energy loss profiles during short duration sliding contacts: a computer-compatible instrument based on the British Pendulum Skid Tester

This paper describes a structurally modified British Pendulum Skid Tester fitted with an optical encoder (2500 pulses per revolution), pulse timing electronics ( resolution) and a computer interface (IBM compatible PIO card). A spring-loaded rectangular slider attached to the foot of the pendulum is driven across a horizontal surface at speeds of up to . By measuring changes in the angular velocity of the pendulum, it is possible to calculate the loss of energy due to friction with 1 mm linear resolution. Values for the path-averaged coefficient of friction for thermoplastic and elastomer sliders can be determined with a precision of around 1%, enabling highly reproducible studies of the influence of slider wear and surface condition on friction losses to be carried out. Energy loss profiles measured during the passage of the slider over the surface can reveal variations in surface roughness as well as details of the slider/substrate interaction. Force profiles for natural rubber sliders travelling over smooth surfaces at speeds in excess of show well-defined stick-slip oscillations in the force of sliding friction.