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Cameron, Timothy
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Prediction of Friction Durability in Off-Road Applications Based on Mechanistic Understanding of the Effects of Fluids and Surfaces on Clutch Friction

Afton Chemical Corporation-Mark Devlin, Atanu Adhvaryu
Komatsu Ltd.-Shinpei Kariwa, Toshiharu Abekawa
  • Technical Paper
  • 2019-01-2339
Published 2019-12-19 by SAE International in United States
After new transmission lubricants are developed there is an extensive validation program where friction durability testing is performed on multiple clutch materials. Each durability test can run for long terms and the entire validation program can take much longer terms. A well designed lubricant and friction material will deliver the necessary friction control for construction equipment to operate at optimum level. A mechanistic construct has been evaluated to calculate friction durability in clutch systems based on fluid and surface tribological properties. Fluid properties include both boundary frictional and rheological effects. Surface properties include elastic modulus, surface roughness, asperity density and asperity tip radius. Using this mechanistic construct friction durability has been predicted. In the past, researchers in the field have often associated lubricant induced glazing of the friction material surface as the cause of the loss of friction control in clutch systems. In the current study, results show that wear is also a dominant cause of friction loss. In short clutch friction tests the rate of change in surface properties and fluid properties have been…
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Effect of Fluid Flow through Clutch Material on Torque Fluctuations in Clutches

Afton Chemical Corporation-Mark Devlin, Darryl Williams, Michael Glasgow, Karen Hux, Aaron Whitworth
Miami University-Timothy Cameron
Published 2016-10-17 by SAE International in United States
Improving vehicle fuel efficiency is a key market driver in the automotive industry. Typically lubricant chemists focus on reducing viscosity and friction to reduce parasitic energy losses in order to improve automotive fuel efficiency. However, in a transmission other factors may be more important. If an engine can operate at high torque levels the conversion of chemical energy in the fuel to mechanical energy is dramatically increased. However high torque levels in transmissions may cause NVH to occur. The proper combination of friction material and fluid can be used to address this issue. Friction in clutches is controlled by asperity friction and hydrodynamic friction. Asperity friction can be controlled with friction modifiers in the ATF. Hydrodynamic friction control is more complex because it involves the flow characteristics of friction materials and complex viscosity properties of the fluid. This paper shows how NVH and torque capacity can be controlled by optimizing the flow characteristics of friction materials and the complex viscosity of fluids.
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