Sustainable C<strong>on</strong>structi<strong>on</strong> and Design <str<strong>on</strong>g>2011</str<strong>on</strong>g> [10] Etsuo Marui, Hiroki Endo. Effect of reciprocating and unidirecti<strong>on</strong>al sliding moti<strong>on</strong> <strong>on</strong> the fricti<strong>on</strong> and wear of copper <strong>on</strong> steel. Wear 249 (2001) 582–591. [11] D.H. Hwang, D.E. Kim, S.J. Lee. Influence of wear particle interacti<strong>on</strong> in the sliding interface <strong>on</strong> fricti<strong>on</strong> of metals. Wear 225-229 (1999) 427-439. [12] D. Odabas, S. Su. A comparis<strong>on</strong> of the reciprocating and c<strong>on</strong>tinuous two-body abrasive wear behavior of soluti<strong>on</strong>-treated and age-hardened 2014 Al alloy. Wear 208 (1997) 25–35. [13] Marcia M. Maru and Deniol K. Tanaka. Influence of Loading, C<strong>on</strong>taminati<strong>on</strong> and Additive <strong>on</strong> the Wear of a Metallic Pair under Rotating and Reciprocating Lubricated Sliding. J. of the Braz. Soc. of Mech. Sci. & Eng. July-September 2006, Vol. XXVIII, No. 3. 278 - 285. 18 Copyright © <str<strong>on</strong>g>2011</str<strong>on</strong>g> by Laboratory Soete
Sustainable C<strong>on</strong>structi<strong>on</strong> and Design <str<strong>on</strong>g>2011</str<strong>on</strong>g> CHARACTERIZATION AND MODELING OF FRICTION AND WEAR: AN OVERVIEW F. Al-Bender 1 , K. De Moerlooze 1,2 1 Katholieke Universiteit Leuven, Dept. Mech. Eng., Div. PMA, Celestijnenlaan 300B, B-3001 Leuven 2 with Leuven Air Bearings N.V. since Sept. 2010 Abstract In this age of virtual design, high-performance machines, and precise moti<strong>on</strong> c<strong>on</strong>trol, the ability to characterize fricti<strong>on</strong> and wear processes and then to model and simulate them, becomes a pertinent issue. This communicati<strong>on</strong> gives a c<strong>on</strong>densed overview of the generic characteristics of fricti<strong>on</strong>, thereafter, generic models, developed at KULeuven, PMA, are presented and discussed. In regard to fricti<strong>on</strong>, both sliding and rolling are c<strong>on</strong>sidered. The characterizati<strong>on</strong> c<strong>on</strong>cerns (i) the relati<strong>on</strong>ship between the fricti<strong>on</strong> (tracti<strong>on</strong>) force and the state of sliding of the system (displacement, velocity,…), at a given normal load; (ii) the relati<strong>on</strong>ship between the coefficient of fricti<strong>on</strong> and the normal load. As regards fricti<strong>on</strong>al behaviour in functi<strong>on</strong> of sliding (rolling) state, the main features are: (i) pre-sliding (prerolling) hysteresis and (ii) gross-sliding (rolling) dynamics. Models are presented that capture those features and relate them to the c<strong>on</strong>tact characteristics. Comparis<strong>on</strong> with experimental results is also presented for the main features. Sec<strong>on</strong>dly, the dependence of the coefficient of fricti<strong>on</strong> <strong>on</strong> the normal load is identified and modelled. Finally, regarding wear simulati<strong>on</strong>, the generic fricti<strong>on</strong> model is extended to cater for an asperity populati<strong>on</strong> that changes during the lifetime of sliding. Based <strong>on</strong> fatigue c<strong>on</strong>siderati<strong>on</strong>s, asperities get broken after a certain number of c<strong>on</strong>tact cycles, and are replaced by smaller <strong>on</strong>es. With the aid of this model, we try to correlate energy dissipati<strong>on</strong> with wear evoluti<strong>on</strong>, and support that by experimental observati<strong>on</strong>. Keywords : Fricti<strong>on</strong>, tracti<strong>on</strong>, wear, normal load, fricti<strong>on</strong> coefficient, theoretical models, experimental results, Stribeck curve, fricti<strong>on</strong> lag, hysteresis, rolling. 1 INTRODUCTION Fricti<strong>on</strong> modelling has been steadily gaining in interest over the last few decades. However, owing to the complexity of the fricti<strong>on</strong> and wear phenomen<strong>on</strong>, no comprehensive, practicable fricti<strong>on</strong> model that shows all of the experimentally observed aspects of fricti<strong>on</strong> force dynamics in <strong>on</strong>e formulati<strong>on</strong> is available. Most available fricti<strong>on</strong> and wear models are, in essence, empirical, that is, based <strong>on</strong> limited observati<strong>on</strong>s and interpretati<strong>on</strong>s. In this sense, the resulting models are valid <strong>on</strong>ly for the specific scope of test c<strong>on</strong>diti<strong>on</strong>s, such as the level and type of excitati<strong>on</strong>, used to obtain the data. On the other hand, development of simulati<strong>on</strong> models and, where possible, predictive theories, at scales from atomic, through c<strong>on</strong>tinuum, to useful engineering models, can fill empty gaps in the toolboxes available to designers and analysts. Besides the field of tribology, where the origin of fricti<strong>on</strong> is <strong>on</strong>e of the main topics, modelling and compensati<strong>on</strong> of fricti<strong>on</strong> dynamics are treated in several other domains. In the machining and assembly industry, demand for high-accuracy positi<strong>on</strong>ing systems and tracking systems is increasing. Research <strong>on</strong> c<strong>on</strong>trolled mechanical systems with fricti<strong>on</strong> is motivated by the increasing demand for these systems. Fricti<strong>on</strong> can severely deteriorate c<strong>on</strong>trol system performance in the form of higher tracking errors, larger settling times, hunting, and stick-slip phenomena. In short, fricti<strong>on</strong> is <strong>on</strong>e of the main players in a wide variety of mechanical systems. This communicati<strong>on</strong> presents an overview of fricti<strong>on</strong> model-building, which starts from the generic mechanisms behind fricti<strong>on</strong> to c<strong>on</strong>struct models that simulate observed macroscopic fricti<strong>on</strong> behaviour. First, basic fricti<strong>on</strong> properties are presented. Then, the generic fricti<strong>on</strong> model is outlined. Hereafter, the relati<strong>on</strong>ship between fricti<strong>on</strong> coefficient and normal load is c<strong>on</strong>sidered from theoretical and experimental point view. A theory for tarctive rolling is then presented with experimental validati<strong>on</strong>. Finally, the gereric fricti<strong>on</strong> model is extended to deal with wear in sliding c<strong>on</strong>tacts. 19 Copyright © <str<strong>on</strong>g>2011</str<strong>on</strong>g> by Laboratory Soete
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