A number of papers published in the past several years (1, 2, 3) have sought to quantify transmission band performance parameters. Most recently researchers have explored the effects of temperature and lubrication levels, and correlation of these factors with vehicle testing (4). For the most part, these papers have focused on optimization of existing band and drum systems, and have assumed that the contribution of friction material to overall system performance remains constant.
Historically, most research concerning friction material performance has focused strictly on energy level per unit of surface area. One recent research effort (5) has found that the speed and inertia components of shift energy are at least as important as the energy itself. In either case, friction coefficients have been assumed constant for a given energy level, while variations in the speed and inertia components of that energy level have not been emphasized.
Subsequent research has shown that friction coefficients can vary with changes in speed and inertia, while total energy level remains constant. These findings demonstrate the limitations of single energy level testing procedures in the development of friction materials and the design of friction elements.
The objectives of this paper are twofold:
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1.
To promote better understanding of friction material fluid transport properties and their relationship to transmission band friction performance.
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2.
To present a rational method for identifying and measuring desired frictional characteristics in existing and proposed friction material formulations, through multi-level testing procedures.