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The Volume 21, No 1, March 2016



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Frequency Capture Characteristics of Gearbox bidirectional rotary Vibration System

Ruqiang Mou, Li Hou, Zhijun Sun, Yongqiao Wei, and Bo Li


https://doi.org/10.20855/ijav.2016.21.1390


According to the characteristics of the gearbox and Lagrange mechanics, in this paper a bidirectional rotary vibration system dynamics model of the gearbox is established, using MATLAB to simulate the model, study the vibration characteristics of the system in both horizontal and vertical directions, and compare it to existing simplified models. Through the analysis of the model, the conditions of the system that produce frequency trapping are studied, and the frequency factors of the system are obtained. The results indicate that reducing eccentric mass, eccentricity, and rotary damping, and increasing damping movement, bearing stiffness, and input torque can improve system response speed and reduce the amplitude, which can avoid frequency trapping of the system. The study provides a theoretical basis for optimization and installation of the gearbox system.


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Acceleration Sensor-based First Resonance Vibration Suppression of a Double-clamped Piezoelectric Beam

Zhi-cheng Qiu, Fan-kong Meng, Jian-da Han, and Jin-guo Liu


https://doi.org/10.20855/ijav.2016.21.1391


This paper investigates resonance vibration suppression under persistent excitation near the first structural resonant frequency of a clamped-clamped (doubly-clamped) piezoelectric flexible beam. In this study, an acceleration sensor is used to measure the resonant vibration. Firstly, the finite element method (FEM) is utilized to derive the dynamics model of the system, and modal analysis is carried out. Secondly, an acceleration feedback-based proportional-integral control algorithm and variable structure control algorithms are designed, and a numerical simulation is performed. Finally, a doubly-clamped piezoelectric flexible beam experimental setup is constructed. Experiments are conducted on resonant vibration suppression using the designed control algorithms. The numerical simulation and experimental results demonstrate that the resonant vibration can be suppressed by using the designed control methods, and the improved variable structure control method shows better control performance in suppressing the resonant vibration.


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Review and Comparison of Variable Step-Size LMS Algorithms

Dariusz Bismor, Krzysztof Czyz, and Zbigniew Ogonowski


https://doi.org/10.20855/ijav.2016.21.1392


The inherent feature of the Least Mean Squares (LMS) algorithm is the step size, and it requires careful adjustment. Small step size, required for small excess mean square error, results in slow convergence. Large step size, needed for fast adaptation, may result in loss of stability. Therefore, many modifications of the LMS algorithm, where the step size changes during the adaptation process depending on some particular characteristics,were and are still being developed. The paper reviews seventeen of the best known variable step-size LMS (VS-LMS) algorithms to the degree of detail that allows to implement them. The performance of the algorithms is compared in three typical applications: parametric identification, line enhancementcbox{,} and adaptive noise cancellation. The paper suggests also one general modification that can simplify the choice of the upper bound for the step size, which is a crucial parameter for many VS-LMS algorithms.


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Modelling and Parameters Study of Piezoceramic Parts of an Electroacoustic Transducers

Nowrouz M. Nouri, Mohammad Riahi, Hamid R. Gharavian and Ali Valipour


https://doi.org/10.20855/ijav.2016.21.1393


Electroacoustic transducers as transmitters and receivers play major role in underwater communication systems. Piezoceramic rings are the most important parts of electroacoustic transducers. In this investigation, attempts were made to use the matrix model and the finite element model to evaluate frequency behaviour of piezoceramic rings. In order to validate the accuracy of the proposed models and the solution algorithm, results obtained from both models were compared with experimental results presented by Radmanovi'{c, et al. Upon confirmation of the obtained results from the two models, the effects of the geometrical parameters on the frequency response of the ring and the surrounding domain in which the ring oscillates were studied. Based on the obtained results, the geometrical parameters have effects on both the frequency resonance of the ring, as well as the value of the electrical impedance. It is also noted that the surrounding domain only causes change on the intensity of the ring's electrical impedance.


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Experimental Evaluation of Flank Wear in Dry Turning from Accelerometer Data

Roger Serra and Wafâa Rmili


https://doi.org/10.20855/ijav.2016.21.1394


This paper presents an experimental evaluation of cutting tool wear based on vibration signals to study the wear development of the cutting tool insert in order to increase machining performance. To achieve this purpose, tool life tests according to ISO standard 3685 have been performed in turning operation under dry cutting conditions. The wear development was studied for thirty cutting tool inserts selected from the same production batch, and used in strictly identical experimental conditions for a statistical study. The vibration signatures acquired during cutting processes have been analysed and contrasted using three signal processing techniques: statistical, temporal and spectral analysis. Results have shown that the dynamic characteristics of tool vibration changed with cutting tool wear development. Furthermore, this vibration analysis exhibited a strong correlation, during machining, between the evolution of flank wear land and vibration responses.


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Nonlinear Torsional Vibration Modeling and Characteristic Study of Planetary Gear Train Processing Device

Sun Zhijun, Hou Li, Chang Qinglin, Wei Yongqiao, and Li Wei


https://doi.org/10.20855/ijav.2016.21.1395


A nonlinear torsional vibration model with meshing errors, time varying meshing stiffness, damping coefficients, and gear backlashes was presented to analyse the nonlinear dynamic behaviour of the planetary gear train system, which was used to machine the Circular-Arc-Tooth-Trace cylindrical gear. Its dimensionless equations of the system were derived, and the solution of the equations was carried out by using the method of numerical integration. The bifurcation diagrams indicated that the system had abundant bifurcation properties with the dimensionless speed, and the damping ratios of meshing pairs could influence the vibration amplitudes and bifurcation characteristic greatly. The phase plane plots and Poincaré maps revealed that the motion state of the system would through the regions such as harmonic response, non-harmonic response, 2T-periodic harmonic response, 4T-periodic harmonic response, quasi-harmonic response, and chaotic response. The chaotic regions will cause the system failure and instabilities, so these regions should be avoided.


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Seat-to-Head Transmissibility and Reading\\ Discomfort of the Seated Subjects Exposed to Whole Body Vibration

Vikas Kumara and V. H. Saran


https://doi.org/10.20855/ijav.2016.21.1396


The transmission of vibration from the vibrating interface to various organs of the human body may influence their functioning during the vibration exposure. Therefore, an experimental study on a vibration simulator has been performed to find the effects of vibration on reading performance, and also to establish the relationship between seat-to-head transmissibility (STHT) with reading difficulty and reduction in reading performance. Twelve seated male subjects were exposed to sinusoidal vibration with three magnitudes (0.5, 1.0 & 1.5 m/s2 rms) at seven different frequencies (4, 5, 6.3, 10, 16, 20, and 25 Hz) in three independent directions (vertical, fore-and-aft, and lateral). The results show that three output measures - STHT, reduction in reading performance, and perceived difficulty in reading - are significantly affected by the frequency of vibration in each direction. All three measures have shown the peak at 4 or 5 Hz in three independent directions of vibration. Another peak at 25 Hz has also been observed for reduction in performance and perceived reading difficulty in vertical direction vibration. The results also show decrease in resonance frequency of the transmissibility with an increase in vibration magnitude, which represents nonlinear behaviour in biodynamic response by the human body.


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On the Instabilities in a Switchable Stiffness System for Vibration Control

Diego Francisco Ledezma-Ramirez, Neil Ferguson, and Michael Brennan


https://doi.org/10.20855/ijav.2016.21.1397


A strategy for vibration control in which the stiffness is switched on and off between a minimum and a maximum value within each oscillation cycle is considered in this study. The strategy has been shown to help greatly in decreasing residual vibrations, thus increasing the effective damping ratio in lightly-damped systems. This work explores the effect of the delay during the stiffness switching. In this study, it is predicted theoretically how a certain value of delay could cause instabilities, and experimental results are presented.


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Vibroacoustic Analysis and Response Suppression of a Rectangular Sandwich Electrorheological Panel

Seyyed M. Hasheminejad, and S. M. Parvasi


https://doi.org/10.20855/ijav.2016.21.1398


A modal summation method based on far-field sound intensity is used to study the average radiation efficiency and the corresponding radiation power of a point-excited, simply-supported, rectangular sandwich plate containing a tunable electrorheological fluid (ERF) core, and set in an infinite rigid baffle. In addition, a classical analytical procedure based on the Rayleigh integral equation method is adopted to investigate the sound transmission characteristics (TL) of the adaptive plate insonified by plane pressure waves at an arbitrary angle of incidence, or excited by a perfectly diffuse sound field with a Gaussian directional distribution of energy. Numerical results reveal the imperative influence of an applied electric field strength (0--3.5~kV/mm) on controlling acoustic radiation from (or sound transmission through) the smart panel in a wide frequency range. In addition, an effort is made to find the optimal electric field which yields improved sound radiation and transmission characteristics for each excitation frequency. Limiting cases are considered and good agreements with the solutions available in the literature used in this study are obtained.


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An Inverse Approach for the Determination of\\ Viscous Damping Model of Fibre Reinforced Plastic Beams using Finite Element Model Updating

Subhajit Mondal, and Sushanta Chakraborty


https://doi.org/10.20855/ijav.2016.21.1399


Investigations have been carried out both numerically and experimentally to settle with a practically feasible set of proportional viscous damping parameters for the accurate prediction of responses of fibre reinforced plastic beams over a chosen frequency range of interest. The methodology needs accurate experimental modal testing, an adequately converged finite element model, a rational basis for correct correlations between these two models, and finally, updating of the finite element model by estimating a pair of global viscous damping coefficients using a gradient-based inverse sensitivity algorithm. The present approach emphasises that the successful estimate of the damping matrix is related to a-priori estimation of material properties, as well. The responses are somewhat accurately predicted using these updated damping parameters over a large frequency range. In the case of plates, determination of in-plane stiffness parameters becomes easier, whereas for beam specimens, transverse material properties play a comparatively greater role and need to be determined. Moreover, for damping matrix parameter estimation, frequency response functions need to be used instead of frequencies and mode shapes. The proposed method of damping matrix identification is able to reproduce frequency response functions accurately even outside the frequency ranges used for identification.


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An Experimental Study on Gear Diagnosis by Using Acoustic Emission Technique

Selçuk Erkaya, Şaban Ulus


https://doi.org/10.20855/ijav.2016.21.1400


Acoustic Emission (AE) is one of the condition monitoring and diagnosing techniques of rotating machine elements such as gears, bearings, etc. So far, many studies about fault diagnosis on gearboxes have been implemented for vibration monitoring. In addition, a great deal of research on spur gears has been done for understanding the possible gear faults by considering their acoustic characteristics. In this study, possible faults in gears were analysed by the AE technique. A single-stage gearbox system comprising both helical and spur gears was used to identify the existence of possible gear faults, such as pitting and cracking at the tooth root. Noise signal in time-domain is converted to frequency-domain by using Fast Fourier Transform (FFT). In the experimental stage, artificial faults were implemented, and some mathematical parameters such as Root Mean Square error (RMS), Crest Factor (CF), and maximum value of noise level were considered to identify the fault occurrence at the meshing gear. The results show that the AE technique is very effective in diagnosing the defects in a gear system by a contactless measurement. Also, compared to the other diagnostic approaches, it is clear that the gear defects can be determined at an earlier stage by the AE technique.


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High Damping Characteristics of an Elastomer Particle Damper

Marcelo Bustamante, Samir N. Y. Gerges, Erasmo F. Vergara, and Jorge P. Arenas


https://doi.org/10.20855/ijav.2016.21.1401


Research testing has led to the development of an Elastomer Particle Damper (EPD), which can add considerable damping to a structure by directing the vibration to a set of interacting elastomer particles through a rigid connection. This vibration treatment presents highly nonlinear behavior that is strongly dependent on both the vibration amplitude and frequency. Curves of damping loss factor (DLF) of an EPD system with vertical motion as a function of frequency and acceleration are reported herein. The results show that the elastomer particle damper has two distinct damping regions. The first region is related to the "fluidization state" of the particles, as described in the literature, obtained when the damper is subjected to vertical acceleration close to 1 g and frequencies below 50 Hz. The second region presents high values of DLF to acceleration values lower than 1 g, and the frequency range is dependent upon the stiffness of the particles. A high degree of effectiveness is achieved when the working frequency of the elastomer particle dampers is tuned to a natural frequency of a plate and when they are strategically located at points having large displacement. The performance of EPDs was compared with that of a commercial constrained layer damping installed in an aircraft floor panel. The EPDs achieved an acceleration level attenuation in the aircraft floor panel similar to that of the commercial constrained layer damping system.


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