Introductory Remarks

Abstract

While I am privileged to act as your chairman during this session, Session II, on the fundamental aspects of rubber friction, we are indeed fortunate to have as speakers, four of the most eminent and active researchers in the field of tire technology. Two of these are from the United Kingdom, one from the German Federal Republic, and one from the U.S.A., and they are all renowned for their basic contributions to the fundamental understanding of the nature of the tire-road frictional contact. Now whereas the emphasis in Session I has been on general topics such as traction under dry, wet, and snowy conditions, the subjects discussed in this session are of a more fundamental and basic nature. Here the physical mechanism of rubber friction will be examined in the light of new or unusual experimental evidence and an attempt will be made to seek some form of agreement and conclusions in areas where perhaps doubt or uncertainty previously existed. We must at least be clear on the roles played by adhesion and hysteresis both with and without the presence of lubricants, and we must accurately assess the influence of material properties, slip speed, temperature, and surface texture in the light of this new experimental evidence. We cannot overemphasize the significance of a fundamental and complete understanding of rubber friction in terms of eventual optimized tire design and ultimately vehicle safety. Those of us who are active in research and development as applied to rubber-like materials are well aware of the truly interdisciplinary nature of tire-to-ground traction. Physics, chemistry, metallurgy, dynamics, tribology, thermodynamics, heat transfer, elasticity, viscoelasticity, rheology, elastohydro-dynamics, and lubrication technology play complex and intertwined roles in determining the magnitude of the frictional coupling that ultimately exists in the contact patch. It has been claimed that at least 50 variables are operative during the simple free rolling of a pneumatic tire. Such complexity necessitates the adoption of a simplistic and intuitive approach in seeking a further understanding of contact friction. All of our speakers today have followed this method, consciously or unconsciously, and have hereby provided remarkable insight into the nature and causes of rubber traction. Such advances are then used by the tire designer who synthesizes, compromises, and improvises until a satisfactory optimized design emerges. But here we emphasize the role played by fundamental and original research and its meaningful interpretation.