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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

Miami University-Timothy Cameron
Afton Chemical Corporation-Mark Devlin, Atanu Adhvaryu
  • 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

Miami University-Timothy Cameron
Afton Chemical Corporation-Mark Devlin, Darryl Williams, Michael Glasgow, Karen Hux, Aaron Whitworth
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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High Transparency Inflatable Modules for Space Habitats

Miami University-Raffi Tomassian
TILT OOD, Bulgaria-Valentin Stavrev
Published 2008-06-29 by SAE International in United States
In reaction to the prevalent space design paradigm, we would like to explore a combination of transparent polymer laminate membranes and high tensile strength webbing as the envelope of future transparent space habitats. Further study reveals fascinating possibilities in the use a tensegrity structures as the exo- or endoskeleton for such envelopes.In the following work we look at thin shell transparent structures as possible observation modules in space habitats or as the domed component for a colony on the moon or another planet. For such structures the internal pressure is not only a load but their shaping force as well, i.e. they are de-facto inflatables. We investigate their feasibility based on available technologies, such as lobed balloons. Other sources of technological transfer are ETFE (ethylene-tetrafluoroethylene copolymer) cushions, safety laminate foils, and hi-tech laminate sails design. We further develop the basic idea of using lobed transparent membranes in space habitats through several case studies. We would finally like to spur a discussion about design process as it relates to inflatable structures.
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Process Design Tool for Rapid Estimation of Titanium Turning Cost

Miami University-James Moller
Technirep, Inc-Donald Shrader
Published 2000-05-16 by SAE International in United States
The design tool developed addresses the need for timely and interactive manufacturing cost estimation early in product and process design. The particular context treated is finish turning of titanium. A collection of simple physical models of the most relevant phenomena are combined in a computer program. Model simplicity enables rapid delivery of results in the form of cutter temperature, force, and wear predictions. Knowledge of the specific nature of titanium machining is included. Cutter wear predictions agree well with experimental data. Process conditions and cutter geometry that result in minimum direct cost can be provided on time scales that are a fraction of the time to actually machine the part. This design tool is most appropriate for cost estimation of jobs in which cutters and/or machining time are a significant part of manufacturing cost. The tool can serve to identify robust process conditions and cutter wear limits in the sense that variation in machining cost for variations about the process operating point can be explored.
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