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1 – 10 of over 11000Shuowen Yan, Pu Xue, Long Liu and M.S. Zahran
This study aims to investigate the design and optimization of landing gear buffers to improve the landing-phase comfort of civil aircraft.
Abstract
Purpose
This study aims to investigate the design and optimization of landing gear buffers to improve the landing-phase comfort of civil aircraft.
Design/methodology/approach
The vibration comfort during the landing and taxiing phases is calculated and evaluated based on the flight-testing data for a type of civil aircraft. The calculation and evaluation are under the guidance of the vibration comfort standard of GB/T13441.1-2007 and related files. The authors establish here a rigid-flexible coupled multibody dynamics finite element model of one full-size aircraft. Furthermore, the authors also implement a dynamic simulation for the landing and taxiing processes. Also, an analysis of how the main parameters of the buffers affect the vibration comfort is presented. Finally, the optimization of the single-chamber and double-chamber buffers in the landing gear is performed considering vibration comfort.
Findings
The double-chamber buffer with optimized parameters in landing gear can improve the vibration comfort of the aircraft during the landing and taxiing phases. Moreover, the comfort index can be increased by 25.6% more than that of a single-chamber type.
Originality/value
To the best of the authors’ knowledge, this study first investigates the evaluation methods and evaluation indexes on the aircraft vibration comfort, then further conducts the optimization of the parameters of landing gear buffer with different structures, so as to improve the comfort of aircraft passengers during landing process. Most of the current studies on aircraft landing gear have focused on the strength and safety of the landing gear, with very limited research on cabin vibration comfort during landing and subsequent taxiing because of the coupling of runway surface unevenness and airframe vibration.
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Su Yong and Gong Wu-Qi
Abnormal vibrations often occur in the liquid oxygen kerosene transmission pipelines of rocket engines, which seriously threaten their safety. Improper handling can result in…
Abstract
Purpose
Abnormal vibrations often occur in the liquid oxygen kerosene transmission pipelines of rocket engines, which seriously threaten their safety. Improper handling can result in failed rocket launches and significant economic losses. Therefore, this paper aims to examine vibrations in transmission pipelines.
Design/methodology/approach
In this study, a three-dimensional high-pressure pipeline model composed of corrugated pipes, multi-section bent pipes, and other auxiliary structures was established. The fluid–solid coupling method was used to analyse vibration characteristics of the pipeline under various external excitations. The simulation results were visualised using MATLAB, and their validity was verified via a thermal test.
Findings
In this study, the vibration mechanism of a complex high-pressure pipeline was examined via a visualisation method. The results showed that the low-frequency vibration of the pipe was caused by fluid self-excited pressure pulsation, whereas the vibration of the engine system caused a high-frequency vibration of the pipeline. The excitation of external pressure pulses did not significantly affect the vibrations of the pipelines. The visualisation results indicated that the severe vibration position of the pipeline thermal test is mainly concentrated between the inlet and outlet and between the two bellows.
Practical implications
The results of this study aid in understanding the causes of abnormal vibrations in rocket engine pipelines.
Originality/value
The causes of different vibration frequencies in the complex pipelines of rocket engines and the propagation characteristics of external vibration excitation were obtained.
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Jinxue Sui, Xia Zhang, Li Yang, Zhilin Zhu and Zhang Xin
Vibration measurement is needed in many industrial production processes, such as equipment monitoring, fault diagnosis, and noise analysis and eliminating and so on. The purpose…
Abstract
Purpose
Vibration measurement is needed in many industrial production processes, such as equipment monitoring, fault diagnosis, and noise analysis and eliminating and so on. The purpose of this paper is to propose a simple vibration testing system which includes the laser, the string, position sensitive detector (PSD) and the corresponding signal processing circuit.
Design/methodology/approach
PSD is an optical semiconductor sensor that can fast locate the luminous spot position precisely, which means that it can output different electric current according to the luminous spot at different position of its surface. Moreover, the experiment on PSD sensor using different vibration source and frequency had been carried out. Finally, the vibration waveform of the luminous spot on PSD photosurface was obtained.
Findings
According to the experimental results, each kind of vibration parameter with different vibration source, such as vibration frequency and amplitude can be calculated.
Originality/value
The experimental results agreed with the actual parameter, which showed PSD not only had its own good qualities in the position measurement, but also had the unique superiority in the vibration measurement.
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Nanshan Wang, Heng Liu, Qidan Wang, Shemiao Qi and Yi Liu
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…
Abstract
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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Mohammad Asaduzzaman Chowdhury and Maksud Helali
The purpose of this paper is to present the frictional behaviour of composite materials under external horizontal vibration. Variation of friction coefficient is investigated…
Abstract
Purpose
The purpose of this paper is to present the frictional behaviour of composite materials under external horizontal vibration. Variation of friction coefficient is investigated experimentally when mild steel pin slides on composite materials such as glass fiber reinforced plastic (GFRP) and cloth reinforced ebonite (commercially known as gear fiber).
Design/methodology/approach
A pin‐on‐disc apparatus having the facility of vibrating the test samples in a horizontal direction is designed and fabricated. Horizontal vibration is created along (longitudinal direction), and perpendicular (transverse direction) to, the sliding direction. The experimental set‐up has the facility to vary the amplitudes and frequencies of vibration while velocity of vibration is kept constant.
Findings
The relative frictional behaviour of these materials and their dimensional analysis are yet to be investigated. Therefore an attempt is made to investigate the relative frictional property of the GFRP and cloth reinforced ebonite (commercially known as gear fiber) and the results of these composite materials are analyzed by dimensional analysis under horizontal vibration.
Practical implications
It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.
Originality/value
It can also be noted that there are no clear correlations between friction‐ and other vibration‐related operating parameters. Considering the above conclusion and lack of correlation, the paper meant to find out a suitable correlation and a way of observing the response of friction force by applying known frequency and amplitude of vibration in a particular direction. It is expected that the application of these results will contribute to the improvement of different concerned mechanical systems.
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THE present series of articles is intended to cover in a general manner the whole subject of vibration in aircraft. The study of aircraft vibration is a specialized branch of…
Abstract
THE present series of articles is intended to cover in a general manner the whole subject of vibration in aircraft. The study of aircraft vibration is a specialized branch of engineering science, calling for considerable practical skill and experience in the design and use of measuring equipment, as well as the ability to carry out the mathematical analyses which render test results intelligible and lead to the successful solution of vibration problems. The leading features of all mechanical vibration problems are, however, of such a nature as to be readily understood, and the aim of this series is to describe these leading features so as to facilitate the appreciation of the broad principles governing the avoidance of unpleasant or dangerous vibrations.
Prabhu Sundaramoorthy, Balaji M., Suresh K., Ezhilventhan Natesan and Mohan K.
The main purpose of this research is to investigate finite-element analysis (FEA) on flux reversal-free stator switched reluctance motor (FRFSSRM) for industrial applications. The…
Abstract
Purpose
The main purpose of this research is to investigate finite-element analysis (FEA) on flux reversal-free stator switched reluctance motor (FRFSSRM) for industrial applications. The vibration analysis for an electrical machine is essential because of the acoustic noises. The acoustic noises originate by coincidence of natural frequencies of motor with the vibration frequencies.
Design/methodology/approach
The identification with the performance for FRFSRM by torque ripple, vibration. The vibration of the machine is because of unbalanced electromagnetic forces. The mutual coupled winding and a common pole between two adjacent exciting poles reduce these unbalanced forces.
Findings
The accelerometer is used to monitor the vibration amplitude in transient mode. A comparison study shows that the vibration is less in the E-core SRM than in the conventional flux reversal SRM.
Originality/value
The shorter flux path reduces the torque ripple and vibration content in SRM. This research article mainly focuses on the parameters such as vibration and torque ripple. The vibration of FRFSRM is identified by accelerometer; ANSYS Package predicts the simulation of the vibration measurement. The dynamic behaviors of this E-core SRM model with rated conditions the vibration had predicted.
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Zhihui Gao, Chao Yun and Yushu Bian
The purpose of this paper is to examine a new idea of vibration control which minimizes joint‐torques and suppresses vibration of the flexible redundant manipulator.
Abstract
Purpose
The purpose of this paper is to examine a new idea of vibration control which minimizes joint‐torques and suppresses vibration of the flexible redundant manipulator.
Design/methodology/approach
Using the kinematics redundancy feature of the flexible redundant manipulator, the self‐motion in the joint space can be properly chosen to both suppress vibration and minimize joint‐torques.
Findings
The study shows that the flexible redundant manipulator still has the second optimization feature on the premise of vibration suppression. The second optimization feature can be used to minimize joint‐torques on the premise of vibration suppression.
Research limitations/implications
To a flexible redundant manipulator, its joint‐torques and vibration can be reduced simultaneously via its kinematics redundancy feature.
Practical implications
The method and algorithm discussed in the paper can be used to minimize joint‐torques and suppress vibration for the flexible redundant manipulator.
Originality/value
The paper contributes to the study on improving dynamic performance of the flexible redundant manipulator via its kinematics redundancy feature. The second optimization capability of the flexible redundant manipulator is discovered and used to both minimize joint‐torques and suppress vibration.
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M.A. Chowdhury and M.M. Helali
The purpose of this paper is to investigate experimentally the effect of external vertical vibration on wear property of mild steel.
Abstract
Purpose
The purpose of this paper is to investigate experimentally the effect of external vertical vibration on wear property of mild steel.
Design/methodology/approach
A pin‐on‐disc apparatus capable of vibrating the test samples in a vertical direction is designed and fabricated. The experimental setup has the ability to vary the amplitudes and frequencies of vibration while velocity of vibration is kept constant. During the experiment, the frequency and amplitude of vibration are varied from 0 to 500 Hz and 0 to 200 μm, respectively.
Findings
Results show that the wear rate decreases with the increase of amplitude and frequency of vibration for mild steel. These results are analyzed by dimensional analysis to correlate the wear rate with sliding velocity, normal load, frequency and amplitude of vibration. The experimental results are also compared with those available in literature and simple physical explanations are provided. Considering the lack of correlation between wear rate and other vibration‐related operating parameters, the present research is started to find out suitable correlation and a way of reducing wear rate by applying known frequency and amplitude of vibration at a particular direction.
Practical implications
It is expected that the applications of these results will contribute to the improvement of different concerned mechanical systems.
Originality/value
The paper can be used for design‐related purposes.
B.O. Al‐Bedoor, L. Ghouti, S.A. Adewusi, Y. Al‐Nassar and M. Abdlsamad
This paper presents experiment results that examine the validity of extracting blade vibration signature from the shaft torsional vibration signals. A special test rig was…
Abstract
This paper presents experiment results that examine the validity of extracting blade vibration signature from the shaft torsional vibration signals. A special test rig was designed and manufactured for this objective. A set of strain gages were bonded to the shaft and to the blades to measure the shaft twisting and blade bending deformations respectively. A controlled frequency exciter excited the blade vibration. The shaft torsional and blade bending vibration signals were simultaneously recorded and presented in the time and frequency domains. The blade bending vibration frequencies appeared dominantly in the shaft torsional vibration signals for all blade vibration frequencies up to 100Hz. For frequencies higher than 100Hz, less sensitivity of the torsional vibration to blade vibration was observed.
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