动力传动系统振动特征FAULT IDENTIFICATION IN DRIVETRAIN COMPONENTS USING VIBRATION SIGNATURE  ANALYSIS

ABSTRACT

The vibration problems associated with bearing, shaft, and gear have drawn attention of much engineering work. The advancements in preventive maintenance of rotor gear transmission systems are currently being sought for the improvement to study a fault diagnosis in the machine health monitoring system. Previously, the analytical procedure is widely employed by researchers and designers of large rotating machinery to study the dynamic behavior of rotating systems. Presently, it has been developed to include different types of fault and used together with some online vibration monitoring methods. These online monitoring methods do not require to shutdown machinery and can be used as an in-flight diagnostic. However, very little work has been carried out on the fault detection under the combination effects of bearing, shaft, and gear in a transmission system.

In this dissertation, both numerical simulations and experimental investigations were performed to identify different damage scenarios involving different combinations of bearing damage, residual shaft bow, and gear tooth damage. The comprehensive numerical models were developed to study the transient response of rotating machinery systems including the effects of inpidually defected components. In order to increase the calculating efficiency and reduce the computational effort, a modal analysis method was applied to the equations of motion and solved the overall dynamics of the system.

The nonlinear bearing force is considered as the result of the contacts between the ball and the raceways using Hertzian contact deformation theory and this model was extended considering the effect of localized defect on inner race. In the case of residual shaft bow, the bow effect was introduced as the forcing function in the equations of motion. In the gear transmission system model, the gear-mesh forces result from a nonlinear periodic gear meshing stiffness. The change in gear surface profile due to wear is modelled as the shift in amplitude of the meshing stiffness. The experimental results used in this study were obtained from the high-speed ball bearing test rig. During these tests, vibration signatures due to each damaged effect: namely bearing defect, residual shaft bow, and gear damage/wear were acquired for identification and validation.

The vibration signatures obtained from both numerical simulations and experiments were examined in the time domain, the frequency domain, and the joint time-frequency domain. The diagnostic

technique was suitably chosen to perform signal analysis for detecting and identifying each damaged characteristic.

The analytical model of gear-rotor-bearing systems was finally extended to investigate the damaged effects under combination scenarios of defects in bearing, shaft, and gear. The numerical results were also validated by those acquired from the test rig experiment. The signature analysis techniques were carefully applied on both numerical and experimental results to examine and characterize its root cause.

CHAPTER I

INTRODUCTION

1.1 Overview

Gears-rotor-bearing system is the most commonly used in rotating machinery such as transmission systems in automobile, aircraft gas turbine, and heavy machinery. During the last three decades, the numbers of usage in gear and bearing systems have substantially increased in both defense and commercial applications. Accounting with the increase in higher operating speed, larger carried load, and lighter weight, the premature failures due to excessive wear and material fatigue occur in components of transmission systems. Such premature failures in the transmission system are always subjected to losses in time and financial or even sometimes they may lead to catastrophic consequences. The fault detection has an important role associated with high speed rotating machinery. This could be a benefit if a fault in components is detected at its early stage so a corrective action can be taken promptly. The preventive maintenance can also