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The Volume 20, No 1, March 2015



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Vibration Monitoring for Defect Diagnosis on a Machine Tool: A Comprehensive Case Study

Mouleeswaran Senthilkumar, Moorthy Vikram, Bhaskaran Pradeep


https://doi.org/10.20855/ijav.2015.20.1362


the application of vibration monitoring and analysis was carried out on a lathe. The characteristic frequencies of tapered roller bearings}, gear mesh frequencies,} and belt drive frequencies were found to locate} the source of vibration. Multi-}harmonics of fundamental defect frequencies were observed. From the} real-time} observation,} e}xperimental prediction of defects has been found to be correct and accurate. This case study shows} that vibration analysis plays a vital role in monitoring the condition of the machine tool.


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Free Vibration Analysis of a Rectangular Duct with Different Axial Boundary Conditions

Pruthviraj Namdeo Chavan and B. Venkatesham


https://doi.org/10.20855/ijav.2015.20.1363


This paper describes the free vibration analysis of a rectangular duct by using the Rayleigh-Ritz method. Static beam functions are used as admissible functions in the Rayleigh-Ritz method. These basis functions are the static solutions of a point-supported beam under a series of sinusoidal loads. The unique advantage of using this method is that it allows for the consideration of different axial boundary conditions of a duct. Computational results are validated with existing literature data for a simply supported rectangular duct and the finite element method (FEM) for other axial boundary conditions. A validated analytical model is used for generating natural frequency data for different dimensions of rectangular ducts. Further curve fitting has been done for the generated data, and an empirical relation has been presented to calculate the first fundamental natural frequency for different material properties of ducts and different axial boundary conditions, which can be used for any dimensions of the duct within the specified range.


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Application of Linear Prediction, Self-Adaptive Noise Cancellation and Spectral Kurtosis in Identifying Natural Damage of a Rolling Element Bearing in a Gearbox

C. Ruiz-Cárcel, E. Hernani-Ros, Y. Cao, M. Corsar, D. Mba, P. Chandra


https://doi.org/10.20855/ijav.2015.20.1364


The ability to detect and diagnose faults in rolling element bearings is crucial for modern maintenance schemes. Several techniques have been developed to improve the ability of fault detection in bearings using vibration monitoring, especially in those cases where the vibration signal is contaminated by background noise. Linear Prediction and Self-Adaptive Noise Cancellation are techniques which can substantially improve the signal to noise ratio of the signal, improving the visibility of the important signal components in the frequency spectrum. Spectral Kurtosis has been shown to improve bearing defect identification by focusing on the frequency band with a high level of impulsiveness. In this paper the ability of these three methods to detect a bearing fault is compared using vibrational data from a specially designed test rig that allowed fast natural degradation of the bearing. The results obtained show that the Spectral Kurtosis was able to detect an incipient fault in the outer race of the bearing much earlier than any other technique.


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Seismic Control of Continuous Bridges Using Variable Radius Friction Pendulum Systems and Viscous Fluid Dampers

A. Krishnamoorthy


https://doi.org/10.20855/ijav.2015.20.1365


This paper investigates the performance of a variable radius friction pendulum system (VRFPS) with supplementary damping using viscous fluid dampers (VFD) to control the seismic response of bridges. A VRFPS is similar to a frictional pendulum system (FPS), but the curvature of the sliding surface is varied, and it becomes the function of the sliding displacement. The bridge is seismically isolated with a VRFPS between the superstructure and the pier, and a VFD is added between the abutment and superstructure. Effectiveness of the proposed system is studied for a three-span continuous bridge isolated with a VRFPS and VFD hybrid system. The performance of a proposed system is compared to a corresponding performance of a hybrid system consisting of a conventional FPS with a VFD. The results of the numerical simulation showed that supplementary damping reduces the seismic response of the isolated bridge. Further, a hybrid system consisting of a VRFPS and a VFD is found to be more effective than a FPS and a VFD hybrid system for seismic control of bridges.


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An Investigations of Sound Absorbance Properties for Weft Knitted Spacer Fabrics

Erhan Sancak


https://doi.org/10.20855/ijav.2015.20.1366


Nonwoven fabrics have been used for many years in different technical applications; they have particularly been used as isolation materials in vehicles in order to reduce the noise heard within them, and they. They have achieved great popularity due to low production cost and good absorbance. However, the fabrics produced by making use of the nonwoven technique have some disadvantages including low resistance, low abrasion strength, poor aesthetic appearance and thickness. In order to eliminate these disadvantages, recent studies have reported that knitted fabrics could be an alternative to nonwoven fabrics. Various studies have focused on the impact on sound absorbance that the thickness and surface structure of knitted fabrics have. In this study, a number of knitted spacer fabrics, which had five different connection angles, were manufactured by using a plain knitting machine. The sound transmission loss levels of the developed fabrics were tested and analysed by Brüel and Kjaer tube instruments. At the end of the examinations, the sound absorbance behaviors at different frequencies were demonstrated in graphics based on the type of knitting. It was determined in the study that three factors have a major impact on the sound absorbance behaviour; thickness of fabric, micro porosity between fabric surfaces and yarn linear density in the interconnection of the fabrics.


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Statistical Evaluation of Complex Sound Environment with Background Noise

Akira Ikuta, Hisako Orimoto, Nazmul H Siddique, Liam Philip Maguire


https://doi.org/10.20855/ijav.2015.20.1367


In order to evaluate noise in a sound environment, it is necessary to estimate the sound levels at evaluation points based on the observations at a reference point. In this study, a method is derived based on the observations contaminated by a background noise to estimate system parameters reflecting several orders of correlation information between the evaluation and reference points in a complex sound environment. Furthermore, a statistical evaluation method for traffic noise under the existence of background noise is proposed. The effectiveness of the proposed method is experimentally confirmed by applying it to the traffic noise data measured in a complex sound environment.


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High Helmholtz Sound Prediction Generated by Confined Flows and Propagation within Ducts

Morteza Bayati; Mehran Tadjfar


https://doi.org/10.20855/ijav.2015.20.1368


A hybrid method for the computation of noise radiation by a confined flow is used in this study. The proposed approach is appropriate and quite powerful for high Helmholtz numbers (i.e. when the turbulence/body interaction region is acoustically non-compact). The validation of this method is checked by comparing it with the analytical results of the tailored Green's function to the spinning of two vortex filaments in an infinite 2-D duct. The method is applied to the prediction of sound in a duct obstructed by a diaphragm. The sound sources generated by the fluctuations in the flow field are computed by means of an incompressible Large Eddy Simulation (LES). These sources are fed into a 2-D acoustic propagation Boundary Element Model (BEM). The predicted total acoustic power is 1.8~dB higher than the result obtained in the literature by Direct Numerical Calculation (DNC) and extrapolated experimental data for the same pipe configuration.


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