The wear and thermo-elastohydrodynamic behavior of thrust washer bearings under non-axisymmetric loads
Jackson, Robert Lee, III
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The goal of this work is to investigate the physical mechanisms that distress thrust washer bearings through physical modeling and numerical techniques. The thrust washer bearing is subjected to non-axisymmetric loads within the planetary gear sets of automatic transmissions in automobiles. In practice the thrust washer bearing often distresses severely and unpredictably, causing transmission breakdown and liability issues. A specially designed thrust washer bearing test rig allows for controlled variation of the operational parameters (speed, load, lubrication flow rate, etc.) governing the tribological behavior of the washer. The test rig also records pertinent real-time data (frictional torque and temperature) from the bearing. In conjunction with the experimental model, a new comprehensive numerical simulation of thrust washer bearings is constructed. The numerical simulation incorporates the effects of macro-scale deformation, micro-scale surface asperity contact, heat generation, boundary and full film lubrication. To model surface asperity contact, the current work performs an extensive finite element study of elasto-plastic spherical contact. The numerical and experimental results show that significant sliding asperity contact can cause high temperatures, high friction, and severe wear.