Effects of Shaft Shape Errors on the Dynamic Characteristics of a Rotor-Bearing System

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Fangxu Sun ◽  
Xianbiao Zhang ◽  
Xing Wang ◽  
Zhenzhong Su ◽  
Dong Wang
Keyword(s):  
Dynamic Characteristics ◽  
Computing Time ◽  
Quantitative Relationship ◽  
System Stability ◽  
Rotating Speed ◽  
Oil Whip ◽  
Rotor Bearing ◽  
Shape Errors ◽  
Reaction Forces ◽  
Bearing System

Effects of shaft shape errors are studied on dynamic characteristics of a rotor-bearing system. Stability characteristics of the cylindrical journal bearing are studied. It is shown that the rotating speed at which the oil whip occurs increases when the shape errors exit. And, there is a threshold speed of the bearing with shaft shape errors; before the speed is increased to the threshold, orbits of the center of the journal decrease, and when the speed exceeds the threshold, the orbits increase dramatically and oil whip appears. Furthermore, the quantitative relationship between shaft shape errors and bearing reaction forces of the rotor-bearing system is obtained, which is verified by experiments using rotors with different machining precisions. In order to reduce computing time, variational principle is applied when solving Reynolds’ equation.

scholarly journals Nonlinear Dynamic Characteristics of Marine Rotor-Bearing System under Heaving Motion

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Yongchao Han ◽  
Ming Li
Keyword(s):  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Dynamic Performance ◽  
Chaotic Oscillation ◽  
Mathematic Model ◽  
Rotating Speed ◽  
Period 2 ◽  
Rotor Bearing ◽  
Motion Period ◽  
Bearing System

In this paper, the influence of the heaving motion on the nonlinear dynamic behavior of the rotor-bearing system is considered. First, a mathematic model of the marine rotor-bearing system is developed on the short bearing theory in the noninertial reference system, in which the heaving motion is taken into account. Then its dynamic characteristics are analyzed based on the numerical integration method, such as the bifurcation diagram, the largest Lyapunov exponents (LLE), the steady-state response, and the rotor orbit and its Poincaré map. The results indicate that heaving motion has a great effect on the dynamics of the rotor system, which exhibits a period 1 motion at low rotating speed, with the increase of the rotating speed, the phenomena of the quasiperiodic, period 2, and double Hopf bifurcations appear. Its dynamic performance presents a period 1 motion, period 2, quasiperiodic, and chaotic oscillation.

Dynamic Analysis of a Motorized Spindle With Externally Pressurized Air Bearings

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Chundong Xu ◽  
Shuyun Jiang
Keyword(s):  
Dynamic Characteristics ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Forced Response ◽  
Air Bearings ◽  
Motorized Spindle ◽  
Static And Dynamic Characteristics ◽  
Rotating Speed ◽  
Rotor Bearing ◽  
Bearing System

The purpose of this paper is to investigate the dynamic characteristics of a motorized spindle with externally pressurized air bearings. The externally pressurized air bearings consist of a journal bearing and a double pad thrust bearing with orifice restrictors. The equations of motion for the rotor-bearing system are established considering five degrees-of-freedom (DOF). The perturbation method and the finite difference method are introduced to calculate the static and dynamic characteristics of the air bearings; and the effects of the rotating speed and tilt angle of the rotor on the dynamic characteristics of the air bearings are analyzed. With the dynamic coefficients of the air bearings and the 5DOF rotor-dynamic model obtained, the stability, the unbalance response, and the forced response of the rotor-bearing system are investigated. Finally, the static and dynamic characteristics of the spindle are verified by an experimental study.

Dynamic analysis of a helical geared rotor-bearing system with composite rotating shafts

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ying-Chung Chen ◽  
Xu Feng Cheng ◽  
Siu-Tong Choi
Keyword(s):  
Composite Material ◽  
Dynamic Analysis ◽  
Dynamic Characteristics ◽  
Mesh Stiffness ◽  
Content Type ◽  
Gear Mesh ◽  
Rotor Bearing ◽  
Rotating Shafts ◽  
Gear Mesh Stiffness ◽  
Bearing System

Purpose This study aims to study the dynamic characteristics of a helical geared rotor-bearing system with composite material rotating shafts. Design/methodology/approach A finite element model of a helical geared rotor-bearing system with composite material rotating shafts is developed, in which the rotating shafts of the system are composed of composite material and modeled as Timoshenko beam; a rigid mass is used to represent the gear and their gyroscopic effect is taken into account; bearings are modeled as linear spring-damper; and the equations of motion are obtained by applying Lagrange’s equation. Natural frequencies, mode description, lateral responses, axial responses, lamination angles, lamination numbers, gear mesh stiffness and bearing damping coefficients are investigated. Findings The desired mechanical properties could be constructed using different lamination numbers and fiber included angles by composite rotating shafts. The frequency of the lateral module decreases as the included angle of the fibers and the principal shaft of the composite material rotating shaft increase. Because of the gear mesh stiffness increase, the resonance frequency of the coupling module of the system decreases, the lateral module is not influenced and the steady-state response decreases. The amplitude of the steady-state lateral and axial responses gradually decreases as the bearing damping coefficient increases. Practical implications The model of a helical geared rotor-bearing system with composite material rotating shafts is established in this paper. The dynamic characteristics of a helical geared rotor-bearing system with composite rotating shafts are investigated. The numerical results of this study can be used as a reference for subsequent personnel research. Originality/value The dynamic characteristics of the geared rotor-bearing system had been reported in some literature. However, the dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts is still rarely investigated. This paper shows some novel results of lateral and axial response results obtained by different lamination angles and different lamination numbers. In the future, it makes valuable contributions for further development of dynamic analysis of a helical geared rotor-bearing system with composite material rotating shafts.

scholarly journals Dynamic Characteristics and Experimental Research of a Two-Span Rotor-Bearing System with Rub-Impact Fault

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Rui Zhu ◽  
Guang-chao Wang ◽  
Qing-peng Han ◽  
An-lei Zhao ◽  
Jian-xing Ren ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Critical Speed ◽  
Great Influence ◽  
Experimental Platform ◽  
Rotating Machine ◽  
Rotor Bearing ◽  
Before And After ◽  
Analysis System ◽  
The Stability ◽  
Bearing System

Rotor rub-impact has a great influence on the stability and safety of a rotating machine. This study develops a dynamic model of a two-span rotor-bearing system with rubbing faults, and numerical simulation is carried out. Moreover, frictional screws are used to simulate a rubbing state by establishing a set of experimental devices that can simulate rotor-stator friction in the rotor system. Through the experimental platform and its analysis system, the rubbing experiment was conducted, and the vibration of the rotor-bearing system before and after the critical speed is observed. Rotors running under normal condition, local slight rubbing, and severe rubbing throughout the entire cycle are simulated. Dynamic trajectories, frequency spectrum diagrams, chart of axis track, and Poincare maps are used to analyze the features of the rotor-bearing system with rub-impact faults under various parameters. The vibration characteristics of rub impact are obtained. Results show that the dynamic characteristics of the rotor-bearing system are affected by the change in velocity and degree of impact friction. The findings are helpful in further understanding the dynamic characteristics of the rub-impact fault of the two-span rotor-bearing system and provide reference for fault diagnosis.

Numerical Simulation of a Bending-Torsion Coupling Gear Transmission System

2013 ◽  
Vol 448-453 ◽  
pp. 3403-3407
Author(s):  
Chao Feng Li ◽  
Shi Hua Zhou ◽  
Jie Liu
Keyword(s):  
Rotation Frequency ◽  
Variable Stiffness ◽  
Rolling Bearing ◽  
Rotational Frequency ◽  
Helical Gear ◽  
Angular Contact Ball Bearing ◽  
Rotating Speed ◽  
Response Characteristics ◽  
Rotor Bearing ◽  
Bearing System

Based on the establishment of angular contact ball bearing mechanical model, a nonlinear coupled lateral, torsional and axial dynamic model of helical gear-rotor-bearing system is established, and the dynamic differential equations of the coupled lateral-torsional-axial nonlinear vibration are deduced for imbalance rotors. The investigations are systematically carried out by oscillograms and spectrograms with rotating speed, taking into account eccentricity and nonlinear supporting by rolling bearing. The results show that the rotation frequency of the driven shaft appears in the driving shaft. In addition, the rotation frequencies and meshing frequency appear obviously in torsional direction. It can be seen that the lateral, torsional and axial response characteristics of driving and driven shafts obvious differences are due to the effects of the gear assembly characteristic, gear geometry parameters and the angular contact ball bearings characteristics. As a result, not only appear the rotational frequency and stiffness frequency, but also yield the bearing variable stiffness frequency and conbined frequency in lateral directions. However, the theory of the helical gear-rotor-bearing system still needs further research.

Reliability Sensitivity Analyses for Oil Whip in Rotor-Bearing System

2012 ◽  
Vol 538-541 ◽  
pp. 1967-1970
Author(s):  
Chang Qing Su ◽  
Yi Yu Sun ◽  
Le Xin Li
Keyword(s):  
High Speed ◽  
Sensitivity Analyses ◽  
Analysis Method ◽  
Random Parameters ◽  
Work Condition ◽  
Oil Whip ◽  
Reliability Sensitivity ◽  
Rotor Bearing ◽  
The Common ◽  
Bearing System

Oil whip phenomenon is the common fault in rotor-bearing system. The reason why oil whip happens often has been researched in high-speed rotor-bearing system. But in practice engineering, due to the requirement of work condition, oil whip cannot be avoided all the time in rotor-bearing system. The paper is based on the relation criterion of oil whip happens in rotor-bearing system, the reliability mode and system reliability of oil whip are defined, and the reliability analysis method for avoiding oil whip in rotor-bearing system is carried out. The effect on reliability sensitivity of random parameters is studied. Numerical results are also presented and discussed.

Experimental dynamic analysis of rod-fastening rotor bearing system with a transverse crack

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nanshan Wang ◽  
Heng Liu ◽  
Qidan Wang ◽  
Shemiao Qi ◽  
Yi Liu
Keyword(s):  
Peer Review ◽  
Dynamic Characteristics ◽  
Vibration Amplitude ◽  
Critical Speed ◽  
Transverse Crack ◽  
Content Type ◽  
Rotor Bearing ◽  
Speed Up ◽  
Rod Fastening Rotor ◽  
Bearing System

Purpose This study aims to obtain the dynamic behaviours of cracked rod-fastening rotor bearing system (RFBS), and experimental investigation was carried out to examine the dynamic characteristics of this kind of assembled rotor bearing system with a transverse crack passing through the critical speed. Design/methodology/approach An experimental test rig of cracked RFBS was established for examining the vibration behaviours between intact and cracked system. The crack on the surface of a fastening rod was simulated by wire-electrode cutting processing method. The comprehensive analysis method of vibration was used to obtain the dynamic characteristics such as vibration amplitude, acceleration and whirling orbits before and after the critical speed as well as the instantaneous response in the process of speed up. Findings Some experimental vibration datum is obtained for cracked RFBS. The appearance of a crack will introduce the initial bending and make the vibration amplitude, acceleration and instant response in the process of speed up increase greatly as well as the change of whirling orbits. Originality/value The actual vibration characteristics for this complex assembled rotor system with a transverse crack are given passing through the critical speed. It can provide some useful help for monitoring the vibration behaviours of this kind of assembled rotor system as well as the detection of the crack fault. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0260/

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