Wearless friction and energy dissipation

Scientific studies of friction can be traced back to several hundreds years ago when the pioneers, Leonardo da Vinci (1452-1519), Amontons (1699), and Coulomb (1785), established the law of friction that friction is proportional to the normal load and independent of the nominal area of contact, which are still being taught today in schools. Since then, scientists and engineers have been trying to answer two fundamental questions where friction comes from and why it exhibits such a behavior as described above. Impressive progress has been made but the mystery of friction has not been resolved yet. In an attempt to interpret the origin of 

An impressive progress in the fundamental study of friction was made more than half a century ago when Bowden and Tabor proposed that friction resulted from shear of adhesive junctions at the real contact area, which took up only a tiny portion of nominal contact zone and was proportional to the load [10], as schematically shown in Fig. 11. The model presents a satisfied explanation as to why friction is proportional to the load and independent of nominal contact area. 

The model proposed by Bowden and Tabor has been regarded as the most successful one for presenting a simple and logical theory capable of explaining the Amontons friction law. However, suspicions concerning the two fundamental assumptions in the model were gradually aroused over past years. Friction has been attributed, in Bowden and Tabor s model, to the adhesion between asperities in contact and torn-off of the adhesive junctions when the shear stress exceeds a critical value. This implies that plastic flow and surface destruction may occur at the moment of slip, and that friction is dominated by the shear strength of the adhesive conjunctions, which is material dependent. 

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The studies on friction originated from sliding-induced instability of interfacial atoms and consequent energy dissipation are reviewed in this section, including the author s work to extend the models of wearless friction. This type of friction has been addressed in the literature by different 

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