Abstract.The necessity to apply a coupled contact interface model including anisotropy for both adhesion and friction is shown via a set of experiments for a rubber surface possessing a periodical waviness, and therefore, an obvious anisotropic structure. The focus of experimental investigations is placed upon the measurements of the global macro characteristics such as global forces and trajectories of a sliding block in order to validate the proposed computational model.

Impacts in forced dynamic systems lead to non-smooth vibrations, showing a scenario of bifurcations. Mechanical and numerical modelling is known for rigid body systems with distinct points of contact. In contrast, continuous systems can have a line of possible contact. As an example a vibrating beam with a delaminated layer will be considered. The objective is to establish a finite element formulation for stationary nonlinear oscillation arising from the evolution of impacts along the contact line between the delaminated layer and the remaining beam. The objectives are focussed on the choice of the unknown values of a set of parameters that mainly describe energy dissipation. A calibration of these parameters can be achieved by experimental results and by investigation of a minimal mechanical model.

In standard stability investigations of structures applying the finite element method usually the bifurcation and snap-through points -so-called stability points -are detected. However, for practical design purposes not only the stable state of equilibrium itself is significant but also the robustness of the state against finite perturbations in contrast to infinitesimal perturbations. The sensitivity measure, which quantifies this robustness, can be investigated by introducing perturbations at certain load levels and considering the perturbed motion. Some sensitivity studies are performed for simple stability problems as well as for realistic structures (cylindrical shells) under different loading conditions. Further scalar parameters based on Liapunov Characteristic Exponents are developed to allow a better judgment of the motion after introducing perturbations and a more efficient analysis of the complex response (see Ewert/Schweizerhof [7]).

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Die mathematische Modellierung eines mechanischen Systems mit Reibung und Stoß führt zur Problematik der Integration von Systemen mit veränderlicher Struktur. Von Interesse ist der Einfluß permanenter Störungen (sowohl physikalisch wie numerisch) auf die orbitale Stabilität der ungestörten Lösung. Hierbei zeigt es sich, daß beide Arten von Störungen sich in ähnlicher Weise auswirken und daß abhängig vom Typ der Lösung unterschiedliche Stabilitätsgrenzen existieren.