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This final report summarizes work on a three-year project devoted to dynamic friction and on control of systems with frictional forces. Detailed theoretical and numerical studies of static and dynamic friction and various phenomena of dynamic friction (stick-slip motion, self-excited oscillations, frictional damping, etc.) are described. Included in the report is also a study of methods of statistical homogenization, devised to develop new micromechanics-based models of contact and friction. The question of optimal control with distributed dynamical systems of viscoelastic bodies with frictional forces is also described. A final component of this study focuses on the mathematical and numerical analysis of elastohydrodynamic lubrication problems and is included in the final chapter. The studies presented in this report provide both a theoretical and numerical basis for modeling contact and friction. These models are shown to produce results in very good qualitative and quantitative agreement with experimental results. Keywords: Friction, Damping, Structural dynamics, Elastohydrodynamic lubrication.

This final report summarizes work on a three-year project devoted to dynamic friction and on control of systems with frictional forces. Detailed theoretical and numerical studies of static and dynamic friction and various phenomena of dynamic friction (stick-slip motion, self-excited oscillations, frictional damping, etc.) are described. Included in the report is also a study of methods of statistical homogenization, devised to develop new micromechanics-based models of contact and friction. The question of optimal control with distributed dynamical systems of viscoelastic bodies with frictional forces is also described. A final component of this study focuses on the mathematical and numerical analysis of elastohydrodynamic lubrication problems and is included in the final chapter. The studies presented in this report provide both a theoretical and numerical basis for modeling contact and friction. These models are shown to produce results in very good qualitative and quantitative agreement with experimental results. Keywords: Friction, Damping, Structural dynamics, Elastohydrodynamic lubrication.

This final report summarizes work on a three-year project devoted to dynamic friction and on control of systems with frictional forces. Detailed theoretical and numerical studies of static and dynamic friction and various phenomena of dynamic friction (stick-slip motion, self-excited oscillations, frictional damping, etc.) are described. Included in the report is also a study of methods of statistical homogenization, devised to develop new micromechanics-based models of contact and friction. The question of optimal control with distributed dynamical systems of viscoelastic bodies with frictional forces is also described. A final component of this study focuses on the mathematical and numerical analysis of elastohydrodynamic lubrication problems and is included in the final chapter. The studies presented in this report provide both a theoretical and numerical basis for modeling contact and friction. These models are shown to produce results in very good qualitative and quantitative agreement with experimental results. Keywords: Friction, Damping, Structural dynamics, Elastohydrodynamic lubrication.

In this report the dynamic behavior of metallic bodies subjected to dry frictional contacts is studied. A simple model of interface response which incorporates a constitutive equation for the normal deformability of the interface and the Coulomb law of friction is developed. This interface model is incorporated in the formulation of problems in continuum mechanics that invlove the contact of linearly elastic or viscoelastic bodies. Variational formulations for these problems are established and existence and uniqueness results are proved for steady-sliding and dynamic frictionless or frictional contact problems. The same interface model is also incorporated in finite dimensional models for contact problems: a simple rigid body model and finite element space discretizations of the continuum models. Numerical studies steady sliding and its dynamic stability are presented, as well as numerical studies of friction-induced oscillations. In the latter case, the Newmark method and the central-difference technique are used to integrate numerically the equations of motion. In the numerical studies particular emphasis is given to the role played by normal degree-of-freedom in frictional sliding.

This document is the final technical report for the project, Computational Methods in Nonlinear Mechanics. The Report summarizes results obtained on this project for the period June 30, 1980 through September 30, 1982. All objectives of the original statement of work have been accomplished. These have included advances in mathematical modelling, numerical analysis, approximation theory, development of computer codes, and the study of related issues connected with the following nonlinear structural problems: contact problems in elasticity, reduced integration and penalty methods for finite element approximations of constrained problems in elasticity and fluid flow, contact problems with friction, nonlinear friction laws, plasticity and metal forming, existence and approximation theories in contact problem in elastostatics, fracture mechanics numerical methods for problems of finite elastic deformation, nonlinear eigenvalue problems, and bifurcation theory. Detailed summaries of results in some of these areas are given together with lists of all papers, reports, books, dissertations and oral presentations produced during the contract period. Suggestions for further research areas are also given. (Author)