(Dr. Itzhak Green, advisor)
"The Wear and Thermo-elastohydrodynamic Behavior of Thrust Washer Bearings Under Non-axisymmetric Loads"
The goal of this thesis is to investigate the conditions that distress thrust washer bearings through physical modeling and numerical techniques. The thrust washer bearing supports non-axisymmetric loads within the planetary gear sets of automatic transmissions and consists of a number of flat-faced washers that are placed between an idle helical gear and its contacting face. Because of non-axisymmetric loading, the gears and washers are tilted in relation to the carrier, forming a converging and diverging gap. Due to such tilt, there are areas of concentrated contact between the components.
To gain an understanding of thrust washer bearing behavior under non-axisymmetric loading, a test rig designed specifically for testing thrust bearings, is used to provide a physical model. The test rig allows 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 physical model, a numerical simulation of thrust washer bearings is being constructed. For this, the boundary element method is being used to model the mechanical deformations. Other numerical methods will also be incorporated to model thermal deformations, dynamic friction, boundary lubrication, asperity contact, and full film lubrication. The model will be a quasi-steady state model.