On the Coefficient of Friction between Rubber and Metal under High Pressure

Abstract

The coefficient of friction between vulcanized natural rubbers or polyurethane elastomers and metals is measured under the pressure up to 900 kg/cm². The effects of several factors on the coefficient of friction are examined and an experimental formula is derived from the experiment in which threaded metal bars are used as a model of metal surfaces. The pressure, the mechanical property of rubber and the geometry of metal surface are considered in the above formula. Moreover, the validity of applying the formula obtained by using screws to the surfaces of rolled sheets or drawn bars with microscopic asperities is discussed. The coefficient of friction decreases with an increasing applied pressure, but approaches a definite value in the range of high pressures. The definite values for the case of using soapsuds and powdered rosin are about 1/5 and 5 times the value for no lubricant respectively.