Friction Induced Vibration In Linear Elastic Media With Distributed Contacts

Materials and mechanical engineering researchers studying wear, fretting, elastic indentation testing and other tribological processes frequently need closed-form solutions for various attributes of contacts. These characteristics include contact law, pressure distribution, internal state of stress induced and the influence of friction. Materials and mechanical engineering researchers studying wear, fretting, elastic indentation testing and other tribological processes frequently need closed-form solutions for various attributes of contacts. These characteristics include contact law, pressure distribution, internal state of stress induced and the influence of friction. These solutions, scattered throughout the applied mechanics literature, are difficult to locate, are presented using a range of solution techniques, and express results in a way that is suitable only for experts in the field. `Mechanics of Elastic Contacts' uses a consistent set of recipes for the solution of all relevant problems, presents results in the simplest possible forms, and contains summaries using tabulated data. This reference source will provide a clear guide to elastic contacts for engineering designers, materials scientists and tribologists irrespective of their level of expertise in this important subject.

The book addresses instability and bifurcation phenomena in frictional contact problems. The treatment of this subject has its roots in previous studies of instability and bifurcation in elastic, thermoelastic or elastic-plastic bodies, and in previous mathematical, mechanical and computational studies of unilateral problems. The salient feature of this book is to put together and develop concepts and tools for stability and bifurcation studies in mechanics, taking into account the inherent non-smoothness and non-associativity (non-symmetry) of unilateral frictional contact laws. The mechanical foundations, the mathematical theory and the computational algorithms for such studies are developed along six chapters written by the lecturers of a CISM course. Those concepts and tools are illustrated not only with enlightening academic examples but also with some demanding industrial applications, related, namely, to the automotive industry.

The aim of this book is to describe an efficient procedure to model dynamical contact problems with friction. This procedure is applied to different practical problems and validated by experiments. Friction contacts are used to transmit forces or to dissipate energy. Examples for dynamical engineering systems with friction are brakes, machine tools, motors, turbines, bearings or wheel-rail systems. A better understanding of friction phenomena can result in improvements like the reduction of noise and maintenance costs, increased life time of machines and improved energy efficiency. Dependent on the features of the friction contact, different contact models and solution methods are applied.

Many scientists and engineers do not realize that, under certain conditions, friction can lead to the formation of new structures at the interface, including in situ tribofilms and various patterns. In turn, these structures-usually formed by destabilization of the stationary sliding regime-can lead to the reduction of friction and wear. Friction-I

Local contact behavior and its interaction with the global dynamics of the system are at the origin of innumerable contact issues concerning several different disciplines like tribology, geophysics, vibration mechanics or fracture mechanics. When two elastic media are in relative motion with a frictional interface, friction induced vibrations arise into the system. By a macroscopic point of view, the “macroscopic stick-slip” scenario occurring during relative motion is characterized by sudden friction force drops (sliding state) along the time, separated by periods of elastic energy accumulation (stick state). Instead, the mode dynamic instability occurs when a vibration mode of the mechanical system becomes unstable, due to frictional contact forces. This kind of instabilities, generated by frictional forces, have been mainly object of papers dealing with specific issues in different domains. In this context, experimental and numerical analyses have been focused here on understanding how the local interface behavior affects the macroscopic frictional response of the system, and, conversely, during instability scenarios. The macroscopic frictional scenarios (macroscopic stick-slip instability, mode coupling instability, stable continuous sliding) arising between two simple elastic media in relative motion have been investigated numerically and experimentally. A newer experimental setup (TRIBOWAVE) has been developed and it allowed to reproduce and to investigate the different scenarios under well-controlled boundary conditions. The same frictional scenarios have been reproduced by transient numerical simulations. A dedicated friction law as a function of adherence (sticking) time has been recovered by means of experimental tests. The obtained friction law has been implemented in the numerical model, leading to a quantitative validation of the simulated scenarios by the experiments. Nonlinear transient simulations, complex eigenvalue analyses and experimental tests allowed for drawing instability maps as a function of system key parameters. The numerical model, validated by the comparison with the experimental global measurements (forces, accelerations/velocity), allowed for investigating the coupling between the local contact behavior (contact status distribution, wave and rupture propagation, precursors) and the system dynamic response during macroscopic stick-slip instability, mode coupling instability and stable continuous sliding. The understanding of the coupling between contact and system dynamics will bring to further improvements on the control of contact instabilities and related wear issues.

The dynamics of dissipative mechanical and structural systems is being investigated at various institutions and laboratories worldwide with ever-increasing sophistication of modeling, analysis and experiments. This book offers a collection of contributions from these research centers that represent the state-of-the-art in the study of friction oscillators. It provides the reader with the fruits of a team effort by leaders in this fascinating field.The topics covered include friction modeling, self-excited friction oscillators, homogeneous frictional systems, unsteady lubricated friction, instantaneous contact geometry, impact damping, friction-induced instability and nonlinear dynamics of stick-slip systems, among other topics.This book gives a comprehensive picture of dynamics of dissipative mechanical and structural systems. It also gives an up-to-date account of the present state of the field. It will be of interest to engineers, rheologists, material scientists, applied mathematicians, physicists and historians of science and technology.

Dynamics with friction: Modeling, analysis and experiments, part II. ch. 1. Interaction of vibration and friction at dry sliding contacts / Daniel P. Hess -- ch. 2. Vibrations and friction-induced instability in discs / John E. Mottershead -- ch. 3. Dynamics of flexible links in kinematic chains / Dan B. Marghitu and Ardeshir Guran -- ch. 4. Solitons, chaos and modal interactions in periodic structures / M.A. Davies and F.C. Moon -- ch. 5. Analysis and modeling of an experimental frictionally excited beam / R.V. Kappagantu and B.F. Feeny -- ch. 6. Transient waves in linear viscoelastic media / Francesco Mainardi -- ch. 7. Dynamic stability and nonlinear parametric vibrations of rectangular plates / G.L. Ostiguy -- ch. 8. Friction modelling and dynamic computation / J.P. Meijaard -- ch. 9. Damping through use of passive and semi-active dry friction forces / Aldo A. Ferri