Contact Stresses Under Combined Pressure and Twist

An analytical solution is presented for the case when an elastic sphere is pressed against an elastic half-space and twisted until complete slip occurs. Formulas are derived for the stress and displacement components, their evaluation is illustrated by numerical examples, and comparisons are made with the results of photoelastic tests. These tests also furnished an experimental verification of the assumption that the tangential-surface traction is proportional at every point to the normal pressure within the sliding-contact area, the proportionality constant being the coefficient of friction.