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Transient Vibration Amplification in Nonlinear Torsional Systems with Application to Vehicle Powertrain

Li, Laihang
http://rave.ohiolink.edu/etdc/view?acc_num=osu1385369839

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
This scholarly research investigates the transient vibration amplification problem in nonlinear torsional systems with application to vehicle engine-clutch damper-transmission system. This particular system includes several discontinuous nonlinear elements such as multi-staged (piecewise linear) stiffness, clearance(s) in the gear pair(s), multi-staged hysteresis and preload. The torsional system is excited by the engine start-up (or shut-down) process with an instantaneous firing frequency from the engine. Transient vibration amplification is observed when the speed passes through the torsional vibration resonance(s). The role of abovementioned nonlinear components in influencing the amplification level is not well understood. Therefore, the development of new or improved analytical, semi-analytical and numerical solutions of a nonlinear system, in time (or order) domain, is the focus of this dissertation. First, the problem is formulated in the context of a generic single-degree-of-freedom torsional system. A new closed form solution of the linear torsional oscillator, given motion input with an instantaneous excitation frequency term, is found. The solution for a linear system is able to approximate the transient response (such as peak to peak value of the amplified displacement) of a piecewise linear oscillator under a rapidly varying frequency. Analytical and semi-analytical methods are utilized next to find the transient envelope and to quantify the amplification level. Second, new closed form solutions of the transient envelopes of torsional displacement, velocity, and acceleration for a linear damped oscillator are developed and verified in the order domain. Analytical approximations of the peak frequency and the corresponding maximum amplification are mathematically derived which are also verified by comparing with previously reported analytical or empirical formulas. Dynamic characteristics of a nonlinear torsional path during the non-stationary process are examined by utilizing numerical and semi-analytical methods. For instance, the transient envelope of the torsional displacement for a slowly varying process is constructed by using the harmonic balance method. Then, new approximations for amplified motions of a nonlinear system under a rapidly varying process are successfully proposed and verified. Third, a four-degree-of-freedom nonlinear model of the engine-clutch damper-transmission system is developed where the instantaneous frequency excitation is from the flywheel motion that includes multiple crank speed orders. This nonlinear model is numerically solved and then successfully validated by comparing predictions with fluctuating speed measurements in a medium duty truck driveline system with a 4-cylinder gasoline engine. Finally, several performance metrics are proposed to correlate the transient motions within the clutch damper with the transient gear rattle in the transmission. The effects of the source (such as the gasoline or diesel engine with 4 or 6 cylinders), torsional path (such as the properties of a multi-staged clutch damper) and receiver (such as the drag torque in the transmission) are examined by using the proposed metrics. Overall, the new closed form solutions and analytical approximations can be utilized to diagnose the transient vibrations of a nonlinear torsional system, while providing scientific interpretations and physical insights.
Rajendra Singh (Advisor)
Ahmet Selamet (Committee Member)
Mo-How Herman Shen (Committee Member)
Junmin Wang (Committee Member)
Jason Dreyer (Committee Member)
Mechanical Engineering
Transient Torsional Vibration, Non-stationary Process, Nonlinear Dynamics, Vehicle Powertrain, Instantaneous Excitation Frequency

Recommended Citations

Citations

  • Li, L. (2013). Transient Vibration Amplification in Nonlinear Torsional Systems with Application to Vehicle Powertrain [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385369839

    APA Style (7th edition)

  • Li, Laihang. Transient Vibration Amplification in Nonlinear Torsional Systems with Application to Vehicle Powertrain. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1385369839.

    MLA Style (8th edition)

  • Li, Laihang. "Transient Vibration Amplification in Nonlinear Torsional Systems with Application to Vehicle Powertrain." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385369839

    Chicago Manual of Style (17th edition)

osu1385369839
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© 2013, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.