The bipotential method: A constructive approach to design the complete contact law with friction and improved numerical algorithms

Nowadays, the concept of convex potential of dissipation is a powerful tool customarily used to model the constitutive dissipative laws. Unfortunately, it fails when applied to Coulomb's dry friction contact, which is shown in this paper by checking the cyclic monotony condition. Next, a new approach, the bipotential method, is presented and successfully applied to the contact law. This enables us to write it in a compact form and to uncover an implicit normality rule structure. The advantages of the new approach are numerous, among which is emphasized a pretty extension of the calculus of variation. Two minimum principles of the so-called bifunctional are presented for contact problems. Next, the bipotential method can be qualified as constitutive in the sense that it suggests improved numerical algorithms. In particular, it is proved that the complete contact law can be rewritten as a projection equation onto Coulomb's cone. Numerical examples show the feasibility of the algorithm and the computer time reduction with respect to other previous numerical approaches. (C) 1998 Elsevier Science Ltd. All rights reserved.