FRICTION INDUCED DAMAGE - PRELIMINARY NUMERICAL-ANALYSIS OF STRESSES WITHIN PAINTED AUTOMOTIVE PLASTICS INDUCED BY LARGE CURVATURE COUNTERFACES

Surface damage to modem plastic automotive fasciae (bumpers) arises as a result of numerous physical 'sliding' contact scenarios. The most c ommon tribological events include fascia contact with fixed obstacles, and fascia to fascia (vehicle to vehicle) sliding contact. The tribol ogically induced stresses may introduce abrasion, shear, tensile, and delamination failure in the paint and the plastic substrate layers. Su bsurface stresses imparted by a large curvature counterface and a thin plastic substrate on a hard foundation are compared using both classi c analytical methods and finite element analysis. This is the first qu antitative study of its kind for aiding in the development of a fricti on induced damage (FID) testing device. Phenomenological insights into FID are presented. Relevant analysis methods for FID are also reviewe d. Both methods investigate a cylindrical counterface and a painted pl astic substrate on a stiff foundation. A thin polymer coating on the c ounterface imparts a sliding frictional coefficient, mu similar to 1.0 . Results of three-dimensional numerical analysis are presented for th e transverse contact stresses between counterfaces of different curvat ure, friction coefficient, and normal force. The subsurface maximum st resses move toward the counterface as the curvature is reduced, and th e numerical calculations for TPO-on-foam substrates indicate the likel ihood that shear initiates the failure in the subsurface. Classic Hert zian calculations are inadequate particularly, when material yielding and shear failure are present. (C) 1997 Elsevier Science S.A.