Date of Award

2021

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Darrell Robinette

Committee Member 1

Jason Blough

Committee Member 2

James De Clerck

Committee Member 3

David Labyak

Abstract

Four studies involving torsional vibration isolation performance of automotive drivetrain components, make up this dissertation. One study features a prototype planetary torsional vibration absorber, a unique device that targets low frequency torsion modes in automotive drivetrains. Two studies feature experiments on several torque converters, clutch locked and open, to validate models of the hardware. The last study details experiments on a centrifugal pendulum absorber in a torque converter, to characterize the viscous friction while submerged in automatic transmission fluid (ATF). The enclosed studies improve the state of the art of drivetrain vibration absorbers and isolators, by introducing a new vibration absorber concept and increasing understanding of the underlying physics of torque converters, lock-up clutch dampers, and centrifugal pendulum absorbers.

The design and test of the planetary torsional vibration absorber concept demonstrated the utility of a gear reduction in increasing the apparent inertia of the absorber. By increasing its apparent inertia, the device successfully attenuated a ~20 Hz mode of vibration, and used less packaging volume and mass than a traditional torsional vibration absorber of equivalent performance.

Various lockup clutch designs were characterized with torque transmissibility frequency response function (TTFRF) measurements while spinning at simulated vehicle operating conditions. This in situ testing lent itself useful in characterizing the speed dependent friction in a lockup clutch damper, while also confirming other damper parameters—like stiffness and damping.

The torque converters were also tested in open mode (lockup clutch not engaged). The open mode testing revealed that the hydrodynamic torque converter transmits enough torsional vibration to excite the damper mode for the turbine damper architectures. The open clutch testing contributes a complete data set—encompassing a wide range of speed ratios—to verify torque converter models with. When comparing the test TTFRFs to model TTFRFs, a discrepancy in the damper mode’s natural frequency was revealed, and it was hypothesized that this error resulted from a reflected inertia effect of the ATF undergoing toroidal flow.

The locked clutch testing provoked some questions about the centrifugal pendulum absorber (CPA)—a component of one of the tested torque converter clutch dampers. To validate an existing CPA model, and to characterize the equivalent viscous damping of the CPA mechanism, TTFRFs of custom made torque converters were measured. The custom hardware included: pinned damper (CPA active), pinned CPA (damper active), and pinned straight spring (CPA and arc spring active). The torques due to friction and viscous damping of the damper were effectively eliminated from the CPA, and the equivalent viscous damping of the CPA characterized.

Available for download on Saturday, January 01, 2022

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