scholarly journals A Two-Disk Extended Jeffcott Rotor Model Distinguishing a Shaft Crack from Other Rotating Asymmetries

2008 ◽  
Vol 2008 ◽  
pp. 1-11 ◽  
Author(s):  
Xi Wu ◽  
Jim Meagher
Keyword(s):  
Torsional Vibration ◽  
Nonlinear Models ◽  
Vibration Response ◽  
Full Spectrum ◽  
Side Load ◽  
Torsional Coupling ◽  
Asymmetric Rotor ◽  
Lateral Modes ◽  
Vibration Signatures ◽  
Cracked Shafts

A mathematical model of a cracked rotor and an asymmetric rotor with two disks representing a turbine and a generator is utilized to study the vibrations due to imbalance and side load. Nonlinearities typically related with a “breathing” crack are included using a Mayes steering function. Numerical simulations demonstrate how the variations of rotor parameters affect the vibration response and the effect of coupling between torsional and lateral modes. Bode, spectrum, and orbit plots are used to show the differences between the vibration signatures associated with cracked shafts versus asymmetric shafts. Results show how nonlinear lateral-torsional coupling shifts the resonance peaks in the torsional vibration response for cracked shafts and asymmetric rotors. The resonance peaks shift depending on the ratio of the lateral-to-torsional natural frequencies with the peak responses occurring at noninteger values of the lateral natural frequency. When the general nonlinear models used in this study are constrained to reduce to linear torsional vibration, the peak responses occur at commonly reported integer ratios. Full spectrum analyses of theXandYvibrations reveal distinct vibration characteristics of both cracked and asymmetric rotors including reverse vibration components. Critical speeds and vibration orders predicted using the models presented herein include and extend diagnostic indicators commonly reported.

Vibration response of coupled rotor systems with crack and misalignment

2010 ◽  
Vol 225 (3) ◽  
pp. 700-713 ◽  
Author(s):  
T H Patel ◽  
M J Zuo ◽  
A K Darpe
Keyword(s):  
Linear Trend ◽  
Crack Size ◽  
Vibration Response ◽  
Full Spectrum ◽  
Rotor Systems ◽  
Crack Location ◽  
Simultaneous Existence ◽  
Fault Growth ◽  
Vibration Signatures ◽  
Misalignment Fault

Earlier research on the vibration signatures of a crack or misalignment fault have typically been attempted considering one fault at a time. The condition of simultaneous existence of crack and misalignment (in addition to unbalance) was ignored. However, prolonged existence of misalignment preload could develop a fatigue crack in the rotor shaft. The present study aims to investigate the steady-sate vibration response of misaligned coupled rotors with a crack on one of the rotor shafts. This is perhaps the first study where unbalance, crack, and misalignment faults are considered simultaneously. Along with the axial and torsional vibration features, a detailed full spectrum analysis is carried out to reveal the fault-specific whirl signatures. Two new whirl parameters δ1 and δ2 were introduced based on differences in forward and backward whirling 1X and 2X spectral components. The influence of misalignment level and type, crack size, and crack location on these parameters is investigated for examining the effect of growth of one fault on the whirl nature of the vibration motion of the rotors with coexisting faults (i.e. unbalance, crack, and misalignment). The effects of a fault growth on the whirl parameters are found to be typical of a fault for crack and parallel misalignment faults. However, for the angularly misaligned rotors, the increase in misalignment level results in decrease/no change in the parameter δ2 in the presence/absence of a crack. This non-linear trend of the δ2 parameter cannot be related to any single fault, but it is typical of the coexisting faults.

Identification of firefly algorithm-based fluctuation coefficient of the exciting torque for vehicle driveline

2018 ◽  
Vol 233 (2) ◽  
pp. 317-326
Author(s):  
Qiaobin Liu ◽  
Wenku Shi ◽  
Zhiyong Chen
Keyword(s):  
Torsional Vibration ◽  
Firefly Algorithm ◽  
Vibration Response ◽  
Theoretical Modelling ◽  
Lumped Mass ◽  
Mass Model ◽  
Engine Torque ◽  
Lumped Mass Model ◽  
Vibration Performance ◽  
Engine Excitation

The unbalanced excitation force and torque generated by an engine that resonate with the natural frequency of drivetrain often causes vibration and noise problems in vehicles. This study aims to comprehensively employ theoretical modelling and experimental identification methods to obtain the fluctuation coefficients of engine excitation torque when a car is in different gear positions. The inherent characteristics of the system are studied on the basis of the four-degree-of-freedom driveline lumped mass model and the longitudinal dynamics model of vehicle. The correctness of the model is verified by torsional vibration test. The second order's engine torque fluctuation coefficients are identified by firefly algorithm according to the curves of flywheel speed in different gears under the acceleration condition of the whole open throttle. The torque obtained by parameter identification is applied to the model, and the torsional vibration response of the system is analysed. The influence of the key parameters on the torsional vibration response of the system is investigated. The study concludes that proper reduction of clutch stiffness can increase clutch damping and half-axle rigidity, which can help improve the torsional vibration performance of the system. This study can provide reference for vehicle drivetrain modelling and torsional vibration control.

A new torsional vibration coupling model for transmission system in diesel generator

2021 ◽  
pp. 146808742110689
Author(s):  
Bin Chen ◽  
Yunbo Hu ◽  
Yibin Guo ◽  
Zhijun Shuai ◽  
Chongpei Liu ◽  
...  
Keyword(s):  
Fault Diagnosis ◽  
Torsional Vibration ◽  
Coupling Model ◽  
Transmission System ◽  
System Matrix ◽  
Diesel Generator ◽  
Lumped Mass ◽  
Proposed Model ◽  
Torsional Coupling ◽  
Vibration Coupling

The coupling between the crankshaft and the camshaft is neglected before in fault diagnosis which may lead to incomplete fault information. In this paper, a new torsional coupling model of a diesel generator transmission system is proposed for fault diagnosis. The natural frequency and forced torsional vibration response of the model are obtained by the system matrix method and Newmark-β method. For the system without considering the lumped mass of camshafts, some key natural frequencies are lost. The vibration dynamics are compared for the transmission system with and without the new coupling model. And important frequency responses are missed in the spectrums of the forced torsional vibration without the new coupling model. Finally, the new coupling model is implemented in fault diagnosis and the cause of an unusual vibration fault is deduced in the simulation, which confirms the feasibility of the proposed model in fault diagnosis.

Study on Bending-Torsional Coupling Vibration of Intermediate Axis

2012 ◽  
Vol 166-169 ◽  
pp. 3180-3183
Author(s):  
Xue Shi Yao ◽  
Chun Long Zheng
Keyword(s):  
Torsional Vibration ◽  
Dynamic Equations ◽  
Optimized Design ◽  
Modal Shape ◽  
Bending Vibration ◽  
Coupling Vibration ◽  
Centrifugal Load ◽  
Torsional Coupling ◽  
Nature Frequency ◽  
Torsional Frequency

In order to find the cause of the cracked intermediate axis in a transmission,the characteristic of the bending vibration，torsional vibration and bending-torsional coupling vibration were studied through the analysis of the nature frequency and modal shape based on prestress.The results show that the fatigue fracture of the axis is mainly due to the resonant torsional frequency and bending-torsional coupling vibration and It is basically demonstrated by experiment.It has been found that the fundamental frequency is increase with the increase in spin axis velocity because of the centrifugal load i.e.prestress.The effets can be accounted for by an adjustment of the stiffness,and the dynamic equations are derived.In the end,it is made the optimized design on the axis,the low inherent frequencies are optimized in order to avoid resonance.The problem of the cracked intermediate axis has been solved.

scholarly journals Experimental Study on the Vibration of an Overhung Rotor with a Propagating Transverse Crack

2002 ◽  
Vol 9 (3) ◽  
pp. 91-104 ◽  
Author(s):  
S.A. Adewusi ◽  
B.O. Al-Bedoor
Keyword(s):  
Experimental Study ◽  
Steady State ◽  
Dynamic Response ◽  
Frequency Spectrum ◽  
Transverse Crack ◽  
Vibration Signal ◽  
Vibration Measurement ◽  
Side Load ◽  
Propagating Crack ◽  
Vibration Signatures

This paper presents an experimental study on the dynamic response of an overhung rotor with a propagating transverse crack. The effects of a propagating transverse crack and side load on the dynamic response of an overhung rotor are investigated in order to identify vibration signatures of a propagating crack in rotating shafts. Startup and steady state vibration signatures were analyzed and presented in the form of Bode plots, Frequency Spectrum Cascades, Frequency Spectrum Waterfalls and orbits. The startup results showed that crack reduces the critical speed and increases the vibration amplitude of the rotor system. It also excites 2X vibration in the startup vibration signatures. The steady state results showed that the propagating crack produces changes in vibration amplitudes of 1X and 2X vibration harmonics and excites 3X harmonic just before fracture. During crack propagation, 1X amplitude may increase or decrease depending on the location of the crack and the direction of vibration measurement while 2X amplitude always increases. The steady state vibration signal of a propagating crack also produces a two-loop orbit.

Dynamic Analysis and Multi-Object Optimization of the Forced Torsional Vibration for Vehicular Multi-Stage Planetary Gears

2011 ◽  
Vol 86 ◽  
pp. 263-267 ◽  
Author(s):  
Hui Liu ◽  
Zhong Chang Cai ◽  
Chang Le Xiang ◽  
Ming Zheng Wang
Keyword(s):  
Steady State ◽  
Time Domain ◽  
Torsional Vibration ◽  
Vibration Response ◽  
Resonance Vibration ◽  
Lumped Parameter Model ◽  
Lagrange Method ◽  
Planetary Gears ◽  
Multi Stage ◽  
Lumped Parameter

On the basis of lumped parameter model and the Lagrange method, the model of powertrain was built. Resonance vibration response and non-resonance vibration response were calculated respectively in time domain and frequency domain, characteristics of forced torsional vibration in steady–state were concluded. Comparability and difference of response of parts in different stage were explained. Multi-object optimization was applied to reduce vibration.

Diesel Reduction Gear Design and System Considerations from a Torsional Vibration Viewpoint

1983 ◽  
Vol 20 (02) ◽  
pp. 159-163
Author(s):  
Gary P. Mowers
Keyword(s):  
Torsional Vibration ◽  
Combustion Engine ◽  
Reduction Gear ◽  
Propulsion Systems ◽  
Vibration Data ◽  
Gear Design ◽  
Design Considerations ◽  
Torsional Coupling ◽  
Coupling Stiffness

Ships propulsion systems consisting of diesel engines and reduction gears are popular due to the ability of the internal combustion engine to operate on the less-expensive heavy fuels. This paper highlights system torsional design considerations that heretofore may not have been appreciated or recognized. Diesel engine misfiring and torsional coupling stiffness variables are addressed to show these effects on shaft stresses and gear overload. The role of the computer in monitoring and recording actual torsional vibration data is presented.

Analysis on Seismic Behavior of Irregular High-Rise RC Structure Using Eccentrically Braces

2011 ◽  
Vol 243-249 ◽  
pp. 4001-4004
Author(s):  
Shi Qun Guo
Keyword(s):  
Seismic Response ◽  
Torsional Vibration ◽  
Seismic Behavior ◽  
Seismic Analysis ◽  
Relative Displacement ◽  
Vibration Response ◽  
The Self ◽  
High Rise ◽  
High Rise Building ◽  
Rc Structure

An anti-seismic analysis about two structures (an irregular high-rise building and the previous structure using eccentrically braces) is performed to study their torsional vibration response in earthquake. The self-vibration character and relative displacement between different floors are compared. It is found that adding some eccentrically braces properly can reduce the response of torsional vibration and other seismic response of the structures efficiently. From the example mentioned in the paper, it is verified that this method is a simple and economical one.

scholarly journals Analysis of torsional vibration effect on the diesel engine block vibration

2020 ◽  
Vol 21 (5) ◽  
pp. 522
Author(s):  
Shiwei Ni ◽  
Yibin Guo ◽  
Binglin Lv ◽  
Donghua Wang ◽  
Wanyou Li ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Diesel Engine ◽  
Torsional Vibration ◽  
Coupling Effect ◽  
Fem Simulation ◽  
Vibration Response ◽  
Engine Block ◽  
Torsional Vibrations ◽  
Low Speed ◽  
Vibration Effect

In this paper, the coupling effect between the crankshaft torsional vibration and the low speed diesel engine block vibration is investigated. Using finite element method (FEM), a model of low speed diesel engine is established to study the vibration response. The mode results of FEM agree very well with the test. The additional torques acting on the low-speed diesel engine caused by torsional vibration are discussed in detail. The vibration response of the low-speed diesel engine considering the effect of torsional vibration is studied using FEM simulation. By analyzing the effect of torsional vibration, the results demonstrate that the crankshaft torsional vibrations have important effects on the engine block vibration. The results from this study can provide useful theoretical guidance to predict vibration of low-speed diesel engine.

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