Specific Heat of Tribological Wear Debris Material

Abstract

Stationary processes of solid friction, heating and wear are analyzed in this paper on the basis of the first principle of thermodynamics. Analytical dependences between physical parameters of a tribological system have been determined. Densities of extensive quantity fluxes are referred to elementary surface and elementary time, which has permitted to include intensive quantities, especially temperature, in the model presented here. Although the discussion is restricted to the phenomenological approach, conclusions regarding some microscopic properties of the matter in the process of fragmentation are drawn directly from the laws of energy and mass conservation. Differences between specific heat of the starting material cp and of the debris produced cp′ are emphasized. The model of the friction process described by Maciąg, M. (2010, “Thermodynamic Model of the Metallic Friction Process,” ASME J. Tribol., 132(3), pp. 1–7) has been modified and a new method of evaluating cp′ is proposed. Results of standard friction and wear testing are used to describe selected tribological systems in quantitative terms based on the thermodynamic model discussed here (Sadowski, J., and Żurowski, W., 1992, “Thermodynamic Aspects of Metals' Wear-Resistance,” Tribol. Lubr. Eng., 3, pp. 152–159). Very high specific heat of tribological wear debris material is found at the moment of the material's production. To conclude, results of theoretical and experimental analysis are discussed and their interpretation is proposed. Applicability of the system magnitudes C and D to modeling of friction and wear is highlighted.