scholarly journals Theoretical and Experimental Study on the Transient Time-Frequency Characteristics of the Bending-Torsional Coupling Motions of a Rub-Impact Dual-Rotor System

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Tian Gao ◽  
Shuqian Cao ◽  
Tiancheng Zhang
Keyword(s):  
Friction Coefficient ◽  
Fault Detection ◽  
High Speed ◽  
Rotor System ◽  
Bending Vibration ◽  
Transient Time ◽  
Rotating Speed ◽  
Time Frequency ◽  
Runge Kutta Method ◽  
Torsional Coupling

This paper focuses on the fault characteristics of the bending and torsional motions of a rub-impact dual-rotor system caused by aircraft flight maneuvers. The equations of the bending-torsional coupling motion of a dual-rotor system are established considering a low-pressure rotor rub-impact fault and the transient barrel roll flight of an aircraft. The 4th Runge-Kutta method with varied steps is used to obtain the bending and torsional responses. Then, the influences of the system parameters, including the rub-impact stiffness, friction coefficient, and rotating speed, on the bending and torsional motions of the dual-rotor system are investigated in detail. At last, a rotor rubbing experiment is carried out, verifying the validity of the simulation results. The results show that the rub-impact stiffness affects bending vibration significantly and the torsional motion is sensitive to the friction coefficient. Correspondingly, the torsional responses show apparent fractional fault frequencies and rotating fault frequencies within the whole region of the rub-impact stiffness. The bending responses can only display fault frequencies at certain rub-impact stiffness. As for the rotating speed, the torsional responses are also more effective than the bending responses for the rub-impact fault detection at the low- and high-speed regions. The results will contribute to a comprehensive basis for the rub-impact fault detection.

scholarly journals Dynamic characteristics of the gear-rotor system in compressed air energy storage considering friction effects

2021 ◽  
Vol 12 (1) ◽  
pp. 677-688
Author(s):  
Xinran Wang ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xingjian Dai ◽  
Haisheng Chen
Keyword(s):  
Energy Storage ◽  
Friction Coefficient ◽  
Dynamic Characteristics ◽  
Surface Friction ◽  
Rotor System ◽  
Compressed Air ◽  
Contact Temperature ◽  
Tooth Surface ◽  
Compressed Air Energy Storage ◽  
Rotating Speed

Abstract. The tooth surface friction effects and the resulting tooth surface contact temperature are important factors for the dynamic characteristics of a gear-rotor system in compressed air energy storage (CAES). Therefore, a 3∘ of freedom finite-element model of the system is set up in which the lubrication state of the gear pair, tooth surface friction, contact temperature of the tooth surface, backlash and unbalanced excitation are considered. The friction coefficient is calculated according to the variation of the lubrication state, and the tooth surface contact temperature is derived based on the friction coefficient. The tooth profile deformation caused by the change in the contact temperature is calculated, and the resulting effects on backlash and comprehensive meshing stiffness are considered. The influence of rotating speed, torque load and viscosity of lubricating oil on the system response is studied, and the variation of the friction coefficient, flash temperature of the tooth surface, pressure of the tooth surface and so on are discussed in detail. The results indicate that when the friction coefficient is derived according to the variation of the lubrication state, the variation of the contact temperature of the tooth surface with rotating speed is quite different from that calculated based on a friction coefficient which is set artificially. This leads to a new variation of the dynamic response of the gear-rotor system, and the method of stabilizing the operation of the system is put forward based on the optimization curve for the operation of the system. The results obtained in this paper will provide a reference for the study and design of a gear-rotor system in CAES.

Fabrication and Properties of Cu-Cr Coatings on the Inner Wall of Steel Pipe by Mechanical Alloying Method

2012 ◽  
Vol 602-604 ◽  
pp. 1663-1666
Author(s):  
Zhong Qing Tian ◽  
Guo Xing Zhang ◽  
Wei Jiu Huang ◽  
Yu Kai Zhu
Keyword(s):  
Friction Coefficient ◽  
Mechanical Alloying ◽  
Coating Thickness ◽  
High Speed ◽  
Testing Machine ◽  
Optical Microscope ◽  
Steel Pipe ◽  
Rotating Speed ◽  
Friction Testing ◽  
Cr Coating

The mechanical alloying method process has been innovatively used to prepare Cu-Cr coating on the inner wall of steel pipe. The effect of the rotating speed on thickness, microhardness and friction coefficient of the Cu-Cr coating was investigated. The coating thickness was measured from all samples using optical microscope. The microhardness was analyzed by Digital Microhardness Tester. The friction coefficient was tested by high speed reciprocating friction testing machine. The results show that the coating thickness is 26, 29 and 31μm at the rotating speed of 200, 250 and 300 rpm. The microhardness of the Cu-Cr coating prepared at 200, 250 and 300 rpm are about 760, 780 and 830 Hv. The friction coefficient of the Cu-Cr coating prepared at 200 rpm are about 0.25, 0.40 and 0.38 at the frequencies of 3, 4 and 5 Hz. The friction coefficient of the Cu-Cr coating prepared at 250 rpm are about 0.30, 0.29 and 0.20 at the frequencies of 3, 4 and 5 Hz. The friction coefficient of the Cu-Cr coating prepared at 300 rpm are about 0.10, 0.13 and 0.09 at the frequencies of 3, 4 and 5 Hz.

scholarly journals Dynamic Characteristics of Gear Coupling and Rotor System in Transmission Process Considering Misalignment and Tooth Contact Analysis

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1336
Author(s):  
Wei Fan ◽  
Hong Lu ◽  
Yongquan Zhang ◽  
Xiangang Su
Keyword(s):  
Finite Element ◽  
Dynamic Model ◽  
Calculation Method ◽  
High Speed ◽  
Low Frequency ◽  
Rotor System ◽  
Integral Approach ◽  
Time Frequency ◽  
Low Frequency Vibration ◽  
Mass Eccentricity

The dynamic vibration of the gear coupling-rotor system (GCRS) caused by misalignment is an important factor of low frequency vibration and noise radiation of the naval marine. The axial misalignment of gear coupling is inevitable owing to mass eccentricity, and is unconstrained in axial direction at high-speed operation. Therefore, the dynamic model of GCRS is proposed, considering gear-coupling misalignment and contact force in this paper. The whole motion differential equation of GCRS is established based on the finite element method. Moreover, the numerical calculation method of meshing force, considering the uniform distribution load on contact surface, is presented, and the mathematical predictive time–frequency characteristics are analyzed by the Newmark stepwise integral approach. Finally, a reduced-scale application of the propulsion shaft system is utilized to validate the effectiveness of the proposed dynamic model. For the sensibility to low-frequency vibration, the natural frequencies and vibration modes of GCRS are analyzed through the processing and analysis of acceleration signal. The experimental dynamic response and main components of vibration are respectively consistent with mathematical results, which demonstrate the effectiveness of the proposed dynamic model of GCRS with misalignment. Furthermore, it also shows that the proposed finite element analysis and calculation method are suitable for complex shafting, providing a novel thought for dynamic analysis of the propeller–shaft–hull coupled system of marine.

Analysis of Stiffness of Viscoelastic-Friction Damper for High-Speed Rotor System

2012 ◽  
Vol 538-541 ◽  
pp. 768-772
Author(s):  
Wen Zhong Li ◽  
Fu Xiang Zhang
Keyword(s):  
Friction Coefficient ◽  
High Speed ◽  
Critical Speed ◽  
Cone Angle ◽  
Rotor System ◽  
Outer Ring ◽  
Axial Stiffness ◽  
Friction Damper ◽  
Damping Material

To reduce the excessive vibration of a high-speed rotor system as it passes its critical speed, a viscoelastic-friction damper(VEFD) are introduced into the support. Its stiffness factor is analyzed. Results show, the stiffness factor decreases with the cone angle increasing among 55-80 degrees monotonically. And it is the same trend when the stiffness of the damping material ring decreases. In the case of friction coefficient among 0.1-0.5, the stiffness factor increases monotonically. So adopted a proper structure, suitably chosen the above parameters and the axial stiffness of the outer-ring, the damper can present appropriate stiffness.

scholarly journals Nonlinear vibration behaviors of marine rotor system coupled with floating raft-airbag-displacement restrictor under ship heaving motion

2021 ◽  
Vol 13 (12) ◽  
pp. 168781402110673
Author(s):  
Xuan Xie ◽  
Ming Li ◽  
Junwei Wang
Keyword(s):  
Nonlinear Vibration ◽  
Rotor System ◽  
Rotating Speed ◽  
Floating Raft ◽  
Runge Kutta Method ◽  
Axis Orbit ◽  
Steady State Responses ◽  
Time Domain Response ◽  
Frequency Domain Response ◽  
State Responses

To study the nonlinear vibration behaviors of rotor system coupled with floating raft-airbag-displacement restrictor under ship heaving motion, the dynamic model is established considering the effect of heaving motion, its steady-state responses are numerically obtained using Runge-Kutta method and the results are surveyed by tools such as the spectrum waterfall diagram, time-domain response, frequency-domain response, axis orbit, and Poincaré map. The effects of rotating speed, ship heaving amplitude, and its frequency on the nonlinear dynamic behavior of the system are mainly studied. The results show that the responses of the rotor and raft are of obvious nonlinear behaviors such as amplitude jumping, bifurcation, and chaos due to the effects of nonlinear oil film force and ship heaving motion. With the increase of rotating speed, the motion of rotor and raft presents quasi-periodic and chaotic vibrations. Ship heaving amplitude and its frequency all have great effect on the vibration of rotor and raft; as heaving amplitude or frequency increases, the motion state of rotor and raft changes, and the amplitude of raft increases significantly. The displacement restrictor can effectively limit the vibrating displacements of the raft when ship heaving amplitude or its frequency is large.

Intellectual Gear Fault Detection Based on Wavelet Time-Frequency Analysis

2013 ◽  
Vol 373-375 ◽  
pp. 762-769 ◽  
Author(s):  
Juan Li Zhou
Keyword(s):  
Fault Detection ◽  
Wavelet Packet ◽  
Wavelet Packet Transform ◽  
Gear System ◽  
Support Vector ◽  
Rotating Speed ◽  
Time Frequency ◽  
Fault Recognition ◽  
Vector Machines ◽  
Gear Fault

In this paper, wavelet packet transform and support vector machines are used to detect gear system faults. Testing signals were obtained by measuring the vibration signals of gear system at different rotating speed for different faults. Vibration feature signals were analyzed using wavelet de-noising. By using wavelet packet transform (WPT), signals were decomposed into different frequency bands. the fault detection is used for calculation of energy percents of every frequency. All these were used for fault recognition using Support vector machine (SVM). SVM and neural network transform results were compared. The research indicates that the de-noised signal is superior to the original one. When dealing with various signals, such as Multi-Faults, the diagnosis identification rates are over 92%. This method can be effectively used not only in engineering diagnosis of different faults of gear system, but also for other machinery fault style classification.

scholarly journals A Hybrid SVD-Based Denoising and Self-Adaptive TMSST for High-Speed Train Axle Bearing Fault Detection

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6025
Author(s):  
Feiyue Deng ◽  
Chao Liu ◽  
Yongqiang Liu ◽  
Rujiang Hao
Keyword(s):  
Fault Detection ◽  
High Speed ◽  
Working Environment ◽  
Permutation Entropy ◽  
Mechanical Equipment ◽  
Noise Interference ◽  
Time Frequency ◽  
Bearing Fault ◽  
Bearing Fault Detection ◽  
Self Adaptive

Fault detection of axle bearings is crucial to promote the safe, efficient, and reliable running of high-speed trains. In recent decades, time−frequency analysis (TFA) techniques have been widely used in mechanical equipment fault diagnoses. Time-reassigned multisynchrosqueezing transform (TMSST), as a novel time−frequency representation (TFR) algorithm, is more suitable for dealing with strong frequency-varying signals. However, TMSST TFR results are subject to noise interference. It is difficult to extract the accurate time−frequency (TF) fault feature of the axle bearing under a complex working environment. In addition, determination of the TMSST algorithm parameters depends on the personnel’s subjective experience. Therefore, the TMSST result has a great randomicity and has the disadvantage of having a poor reliability. To address the above issues, a hybrid SVD-based denoising and self-adaptive TMSST is proposed for axle bearing fault detection in this paper. The main improvements of the proposed algorithm include the following two aspects: (1) An SVD-based denoising method using the maximum SV mean to determine the reasonable SV order is adopted to eliminate noise interference and to reserve useful fault impulse information. (2) A new evaluation metric, named time−frequency spectrum permutation entropy (TFS-PEn), is put forward for the quantitative evaluation of the performance of TFR for the TMSST, and then a water cycle algorithm (WCA)-based optimized TMSST can adaptively determine the optimal algorithm parameters. In both the simulation and experimental tests, the superiority and effectiveness of the proposed method is compared with the TMSST, short-time Fourier transform (STFT), MSST, wavelet transform (WT), and Hilbert-Huang transform (HHT) methods. The results show that the proposed algorithm has a better performance for extracting the weak fault features of axle bearing under a strong background noise environment.

Fabrication and Properties of Al-Cr Coatings on the Inner Wall of Steel Pipe by Mechanical Alloying Method

2013 ◽  
Vol 537 ◽  
pp. 279-282 ◽  
Author(s):  
Zhong Qing Tian ◽  
Guo Xing Zhang ◽  
Wei Jiu Huang ◽  
Yu Kai Zhu
Keyword(s):  
Friction Coefficient ◽  
Mechanical Alloying ◽  
Coating Thickness ◽  
High Speed ◽  
Testing Machine ◽  
Steel Pipe ◽  
Interparticle Contact ◽  
Rotating Speed ◽  
Friction Testing ◽  
Cr Coating

Surface coatings; Mechanical alloying; Microstructure; Tribological properties Abstract. The mechanical alloying method process has been innovatively used to prepare Al-Cr coating on the inner wall of steel pipe. The coating thickness was measured from all samples using optical and Scanning Electron Microscope was used to observe the surface microstructure of Al-Cr coating. Microhardness was analyzed by Digital Microhardness Tester. A wear test was performed by high speed reciprocating friction testing machine. The results show that the coating thickness is 20μm and 26μm at the rotating speed of 200 rpm and 300 rpm, respectively. The surface morphology is significantly influenced by the the rotating speed. When the rotating speed was 200 rpm, a heterogeneous coating surface consisting of flattened particles produced by cold welding with less interparticle contact is formed. When the rotating speed was 300 rpm, the coating became denser and a smooth, highly consolidated and dense coating is formed. The hardness of the Al–Cr coating prepared at 200 and 300 rpm are about 250 Hv and 270 Hv. The friction coefficient of the Al–Cr coating prepared at 200 rpm are about 0.37, 0.39 and 0.24 at the frequencies of 3, 4 and 5 Hz. The friction coefficient of the Al-Cr coating prepared at 300 rpm are about 0.3, 0.18 and 0.28 at the frequencies of 3, 4 and 5 Hz.

Rub-Impact Detection of Rotor Systems Using Time-Frequency Techniques

2016 ◽  
Author(s):  
Laihao Yang ◽  
Xuefeng Chen ◽  
Shibin Wang ◽  
Hao Zuo
Keyword(s):  
Contact Force ◽  
High Speed ◽  
High Efficiency ◽  
Rotor System ◽  
Fast Time ◽  
Time Varying ◽  
Rotor Systems ◽  
Time Frequency ◽  
Jeffcott Rotor ◽  
Vibration Responses

Since increasing demands for high efficiency of high speed rotating machines in recent years, the clearance between rotor and stator becomes smaller and smaller. Consequently, rub-impact fault is more likely to occur. It has become one of the most common and serious malfunctions for rotor system in practical engineering. Because the rub-impact severely induces the rotor dynamic instability, it will finally result in catastrophic failures and great economic loss if undetected in time. The occurrence of the rub-impact leads to a contact force between rotating shaft and stator which can be regarded as an additional support on the rotor system. The contact force will further result in the stiffening effect. As a result, some fast time-varying phenomena of vibration responses including the fast time-varying transient stiffness and the fast oscillated instantaneous frequency (IF) may appear. These phenomena may offer abundant characteristics to diagnose the rub-impact fault of rotor system. In this paper, an effective method based on the fast oscillated characteristics of IF for vibration responses is proposed to detect rub-impact fault of rotor bearing system. First of all, the fast time-varying transient stiffness of rub-impact rotor system is qualitatively formulated based on the Jeffcott rotor model and the fast oscillated characteristics of IF is presented and theoretically analyzed. Second, a time-frequency technique called nonlinear squeezing time-frequency transform (NSTFT) is introduced to extract the fast oscillated IF resulting from the rub-impact fault of rotor systems. Numerical simulations are respectively conducted on the Jeffcott rotor system with linear stiffness and oil film bearings. And then the oscillated characteristics of the IF are analyzed. The analysis results suggest that the IF of the vibration responses remains constant at the rotating frequency if there is no rub-impact fault. However, if rub-impact fault occurs, the IF of the vibration responses will oscillate periodically around the basic harmonic frequency. Furthermore, the oscillation law of the IF of vibration responses for rub-impact rotor systems is also numerically investigated. It is found that the oscillation frequency is the 1/k (k = 1, 2, 3, ...) of the rotating frequency if the rotor system operates at periodic-k motion. Finally, rub-impact fault experiments are performed under different operating regimes. The experimental results are consistent with the numerical results, thus demonstrating the validity and the practicability of the proposed method.

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