Subsurface Cracks Under Conditions of Slip, Stick, and Separation Caused by a Moving Compressive Load

The Mode I and II stress intensity factors (K_I, K_II) at the two tips of a subsurface crack subjected to a moving compressive load are studied. Coulomb friction along the crack faces results in a number of history dependent slip-stick configurations and nonsymmetric variation in K_I and K_II. The formulation used to study this variation involves a singular integral equation in two variables which must be solved numerically, and because of the history dependence, requires an incremental solution. Crack lengths and coefficients of friction that result in as many as three zones for any load location are considered in this paper, while a previous paper (Sheppard et al., in press) was limited to configurations involving two zones only.