Friction coefficient evaluation using physically based viscoplasticity model at the contact region during high velocity sliding

Many physical systems require the description of mechanical interactions across interfaces if they are to be successfully analyzed. One of the well-known examples of such a system in the engineering world is the metal to metal friction. This is a complex process that needs to be adequately identified by a constitutive relation in order to better facilitate the design components in severe contact stress applications. In this paper, the formulation of Molinari et al.'s work (J Tribology Trans ASME 35-41, 1999) is revisited in order to investigate the coefficient of dry friction for steel on steel in the high velocity range using physically based viscoplastic constitutive relations. First some of the errors in the work are corrected, and their results are regenerated. The phenomenological constitutive relation used in Molinari et al. (J Tribology Trans ASME 35-41, 1999) is then replaced by the physically based viscoplastic model used in this paper. This constitutive model is implemented into ABAQUS (Analysis User's Manual, 2008) as user-defined subroutine as VUMAT in order to obtain the stress-strain curves at different strain rates and various temperatures. It is shown that the material responses obtained from the simulation using the physically based constitutive viscoplastic model agree well with the real behavior of the metals. Comparing this proposed work with that of Molinari et al. (J Tribology Trans ASME 35-41, 1999) one observes that the proposed theory and constitutive model are superior to the one presented by Molinari et al. This is specifically the case for the artificial shape of softening in the curve. �� Springer-Verlag 2010.Acknowledgments The first author acknowledges the financial support provided for this research by the AFSOR through the Air Force Institute of Technology at WPAFB, Ohio, under Grant No. FA8601-07-P-0302. The author also gratefully acknowledges Professor Anthony N. Palazotto of the Air Force Institute of Technology at WPAFB, Ohio for the many discussions he had on this research. The second author acknowledges the financial support provided for his research from the Science and Technology Council of Turkey (TUBITAK) under the 2219 International Postdoctoral Research Scholarship Program. The authors also appreciate the discussions with Professor Alexis Rusinek regarding the corrections to the Molinari et al. [25] formulation and parameter evaluation. The first author acknowledges the collaboration with Professor Taehyo Park of the Hanyang University, Seoul, Korea, under the World Class University project funded by the National Research Foundation of Korea