Localized asymmetric crack closure with stick-slip in the contact

An idealized problem is solved revealing several new contact and stick-slip configurations in partially closed cracks subjected to mixed mode in-plane loading. An initially open crack under remote tension is closed locally by two concentrated line loads whichpinch the crack shut. The reverse situation with localized separation due to line loads which pry the crack open is also investigated. The line loads may be placed such that isolated closure (or separation) removed from either one or the other, or both crack tips may be obtained. Examples of results for all of the possible contact configurations are presented. Remote shear stress is also considered, the various stick-slip patterns are delineated, and frictional history effects are discussed. Results for the actual contact and stick-slip status, contact tractions, mode I and II crack opening displacements and stress intensity factors are presented in parameter studies of the variation of the magnitude and position of the line loads. The mode I results are based on a new exact solution of the normal stress integral equations, while the mode II results are derived numerically from the shear stress integral equations with frictional shear tractions calculated from the mode I solution for the contact stress. Applications of this type of problem include reinforcement to arrest slow crack growth and mixed-mode fatigue crack closure due to either cyclic stationary loading or traveling loads.