LINEAR AND NONLINEAR MODELS FOR IMPACT WITH FRICTION
Jürgen Jäger, Blattwiesenstr. 7, D-76227 Karlsruhe, Germany,
Comp. Meth. in Contact Mechanics III, eds: M. H. Aliabadi, A. Samartin, CMP, Southampton, 1997, 41-48
Abstract: Plane elastic impact with friction is analysed for different surfaces in the vicinity of the contact area, under the assumption of large half-spaces in contact. For the special case of a flat punch, the force displacement relation is linear and Newton's equation of motion can be solved analytically, when the inertia matrix is uncoupled. Frictional contact of general axisymmetric surfaces can be solved with J„ger's principle for similar materials in contact. Comparison of the results for different surfaces shows that the linear model predicts the rebound angle of the contact point sufficiently accurate, while the impact duration and the local pressure can only be calulated with the nonlinear model. This gives a criterion for the applicability of linear mass-damper models for oblique impact, which are in wide use by many authors. Such models are recommended as a first approximation for nonlinear frictional impact, before time consuming FEM or BEM methods are employed. A simple experiment for oblique impact, which records the impact process without photo or video devices, is shortly described.