Friction and wear of highly-elastic solids

It is shown that the normal forces set up by large shear deformations make sliding impossible when a critical compressive deformation, of the order of 10%, is imposed on a sliding block of highly-elastic material. When the compressive load is maintained constant, rather than the deformation, the way in which the compressive stress is distributed leads to sliding only by means of slip bands which originate at the leading edge of the block and then pass through the contact zone from front to back, as found by Schallamach¹. Thus, a discontinuity is predicted in frictional sliding as the compressive stress is increased from zero, and this occurs at a critical value which depends upon the coefficient of friction, the shear modulus of the material, and the detailed shape of the contact zone. Corresponding changes in wear behavior are inferred.