Repeated Loading, Residual Stresses, Shakedown, and Tribology

Protective residual stresses may be developed in the near surface layers of tribological contacts which enable loads sufficiently large to cause initial plastic deformation to be accommodated purely elastically in the longer term. This is the process of shakedown and, although the underlying principles can be demonstrated by reference to relatively simple stress systems, the situation is complex under a moving Hertzian pressure distribution. Bounding theorems can be used to generate appropriate load or shakedown limits not only for uniform half-spaces but also those with plastic and/or elastic properties which vary with depth. In this way, shakedown maps, which delineate the boundaries between potentially safe and unsafe operating conditions, can be generated for both hardened and coated surfaces.