Boundary element modelling of a coating-substrate composite under an elastic, Hertzian type pressure field: cylinder on flat contact geometry

The boundary element model (BEM) approach is established as a surface engineering tool on standard personal computers with reasonable computation times. Modelling of a cylinder-flat contact is presented. The effects of changing material and geometric parameters on stresses is analysed. For homogeneous materials the validity of the useful half space assumption (HSA) is shown to depend on the relative dimensions of the specimen; i.e. the ratio of real sizes over the Hertz contact half width. For coated systems the numerical results reveal the existence of two major local stress maxima whose exact locations depend on the geometry and the materials parameters. In addition, a step discontinuity in sub-surface stress is seen to exist at the coating-substrate interface. The details of the sub-surface stress field depend crucially on the ratio of coating and substrate Young's moduli as well as the relative coating thickness. Another key parameter is the difference between the Poisson ratios of the materials. (C) 1998 Elsevier Science S.A.