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The Volume 21, No 2, June 2016



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10.20855/ijav.2016.21.1E80

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Dynamic Stability Analysis of a Circularly Tapered Rotating Beam Subjected to Axial Pulsating Load and Thermal Gradient under Various Boundary Conditions

Rashmita Parida and Pusparaj Dash


https://doi.org/10.20855/ijav.2016.21.2402


The dynamic stability of a circularly tapered rotating beam subjected to a pulsating axial external excitation with thermal gradient was studied for all possible combinations of clamped, guided, pinned, fixed, and free boundary conditions. The equations of motion and associated boundary conditions were obtained using the extended Hamilton's principle. Then these equations of motion and the associated boundary conditions were non-dimensionalised. A set of Hill's equations were obtained from the non-dimensional equations of motion by the application of the extended Galerkin method. The zones of parametric instability were obtained using Saito-Otomi conditions. The effects of various boundary conditions, thermal gradient, taper, and rotational speed on the regions of parametric instability were investigated and presented through a series of graphs. The results reveal that increasing rotational speed and taper have stabilizing effects, whereas increasing thermal gradient has a destabilizing effect for all boundary conditions of the beam.


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Method for Evaluating the Statistical Relationship between Sound Pressure Level and Noise Annoyance Based on a Nonlinear Time Series Regression Model and an Experiment

Hisako Orimoto, Akira Ikuta and Yegui Xiao


https://doi.org/10.20855/ijav.2016.21.2403


Identifying the quantitative relationship between the sound pressure level and noise annoyance for environmental noises is important from the viewpoint of noise assessment. In this study, a method for predicting the probabilistic evaluation quantities like L_x ((100 - x) percentile level) and L(Aeq) (equivalent A-weighted sound pressure level) of the noise environment is proposed by introducing a nonlinear time series regression model between the sound pressure level and noise annoyance. More specifically, the joint probability distribution is expanded in an orthonormal expansion series in which linear and nonlinear correlation information is reflected hierarchically in each expansion coefficient. Next, statistical methods for predicting the sound pressure level and the noise annoyance are proposed by introducing a nonlinear time series regression model based on the above probability distribution. The validity of the proposed method is confirmed by applying it to a set of instantaneous data on sound pressure level and noise annoyance observed in a real sound environment.


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Multi-objective Optimization of a Multi-chamber Perforated Muffler Using an Approximate Model and Genetic Algorithm

Shuguang Zuo, Kaijun Wei and Xudong Wu


https://doi.org/10.20855/ijav.2016.21.2405


Perforated mufflers are widely used in automotive intake and exhaust systems and need to be properly designed. However, multi-objective optimization in practical perforated muffler designs usually involves finite element or boundary element models, which demand a higher computation time for evolutionary algorithms. In this paper, an approximate model for transmission loss (TL) predictions is established by correcting the thickness correction coefficient in the transfer matrix using the data calculated by the finite element model (FEM). The approximate model is computationally cheap and applicable for TL predictions above the plane wave cut-off frequency. A popular evolutionary algorithm, NSGA-?, amalgamated with the approximate model, has been adopted to carry out the multi-objective optimization of a multi-chamber perforated muffler. The goals of optimization are to maximize TL at the target frequency range, as well as to minimize the valleys of TL and the size of the muffler. Both transmission loss and insertion loss of the optimized muffler are measured. Numerical and experimental results are in good agreement and show significant improvements of acoustic performance precisely at the target frequency range. Consequently, the combination of the approximate model and the NSGA-? algorithm provides a fast, effective, and robust approach to co-axial perforated muffler optimization problems.


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Developing Vibration Equations of an Orthotropic Wrapped Shell, Considering Residual Stress Effects; A Mathematical Approach

Amirali Sadeqi, Mojtaba Mahzoon and Mohammad Hassan Kadivar


https://doi.org/10.20855/ijav.2016.21.2406


In this paper, vibration equations of an orthotropic, thin rectangular plate wrapped around a porous drum are developed, considering residual stress effects. It is assumed that the plate is subjected to tension from both opposite sides and wrapped continuously around a cylindrical drum so that the wrapped portion behaves like a circular cylindrical shell. First of all, the Lame' parameters, required to constitute the geometry relations, are established for typical cylindrical shallow shell in cylindrical coordinate system. Then, the equations of motion are derived by utilizing the stored strain energy principle based on the Love assumptions. Finally, a set of more complete vibration equations is introduced by applying the simplifications of the Donnell-Mushtari-Vlasov theory. The equations derived under more stringent and precise assumptions are compared with those obtained and available in literature, and the discripancies are highlighted. The present study only aims to mathematically develop the governing relationships, where a numerical solution separately done by the authors can be found in other literature in which vibrational behavior has been completely discussed for moving and stable anisotropic wrapped plates.


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Vibration Analysis of Cracked Beams Using Adomian Decomposition Method and Non-Baseline Damage Detection via High-Pass Filters

Qibo Mao


https://doi.org/10.20855/ijav.2016.21.2408


The Adomian decomposition method (ADM) and high-pass filters are employed in this study to investigate the free vibrations and damage detection of cracked Euler-Bernoulli beams. Based on the ADM and employing some simple mathematical operations, the closed-form series solution of the mode shapes can be determined for beams consisting of an arbitrary number of cracks under general boundary conditions in a recursive way. Then, a high-pass filter is used to extract the irregularity profile from the corresponding mode shape. The location and size of the cracks in the beam can be determined by the peak value of the irregularity profile. The numerical results for different locations and depths of cracks on the damaged beam under different boundary conditions are presented. The results show that the proposed method is effective and accurate. The experimental work for aluminium cantilever beams with one and two cracks was performed to verify the proposed method. The successful detection of cracks in the beam demonstrates that the proposed method has great potential in crack detection of beam-type structures, as it is simple and does not require the mode shapes of an uncracked beam as a baseline.


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Vibration Analysis of Non-homogenous Orthotropic Visco-elastic Rectangular Plate of Parabolically Varying Thickness with Thermal Effect

Pooja Singhal and Arun Kumar Gupta


https://doi.org/10.20855/ijav.2016.21.2409


The present work analyses the vibration behaviour of non-homogeneous orthotropic visco-elastic rectangular plate of parabolically varying thickness on the basis of classical plate theory when the all edges are clamped and are subjected to linearly thermal variation. For non-homogeneity of the plate material it is assumed that the density of the plate material varies parabolically along the x-direction. For visco-elastic materials, basic elastic and viscous elements are combined. The Kelvin model for visco-elasticity is considered here, which is a combination of elastic and viscous elements connected in parallel. Using the separation of variable method, the governing differential equation has been solved. The time period and deflection corresponding to the first two modes of vibrations of clamped plates have been calculated for different values of thermal gradients, non-homogeneity constants, taper constants, and aspect ratio, with the help of Rayleigh-Ritz techniques, and are shown by graphs.


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Characterisation of Major Fault Detection Features and Techniques for the Condition-Based Monitoring of High-speed Centrifugal Blowers

Samer Gowid, Roger Dixon and Saud Ghani


https://doi.org/10.20855/ijav.2016.21.2410


This paper investigates and characterises the major fault detection signal features and techniques for the diagnostics of rotating element bearings and air leakage faults in high-speed centrifugal blowers. The investigation is based on time domain and frequency domain analysis, as well as on process information, vibration, and acoustic emission fault detection techniques. The results showed that the data analysis method applied in this study is effective, as it yielded a detection accuracy of 100%. A lookup table was compiled to provide an integrated solution for the developer of Condition-Based Monitoring (CBM) applications of centrifugal blowers. The major contribution of this paper is the integration and characterisation of the major fault detection features and techniques.


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Experimental and Theoretical Approach to Generalized Empirical Data-based Model of Noise in Ceiling Fan

Rupesh V. Bhortake and Dr. Bimlesh Kumar


https://doi.org/10.20855/ijav.2016.21.2412


This study investigates the design of experimental work to be executed for establishing an approximate generalized empirical model for the noise of a ceiling fan on the basis of experimental data and the methodology of engineering experimentation. It includes the design of an experimental setup, the formulation of a generalized empirical data-based model, that model's sensitivity analysis, and reliability and optimization for the analysis of ceiling fan noise. The formulation and analysis of the noise model are completely covered in this paper to analyse the impact of various input parameters on the output parameter, i.e. the noise of a ceiling fan.


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An Investigation of Initial Shock Cell Formation in Turbulent Coanda Wall Jets

Caroline P. Lubert, Christian R. Schwantes and Richard J. Shafer


https://doi.org/10.20855/ijav.2016.21.2413


Turbulent Coanda wall jets are present in a multitude of applications. Their obvious advantages for flow deflection are often outweighed by disadvantages related to the increased noise levels associated with such jets. Better predictions of Coanda jet noise would allow the Coanda effect to be more widely applied, and its potential to be fully realized. This paper applies the method of characteristics to a steady two-dimensional axisymmetric supersonic flow in order to determine the location of the first shock cell downstream of the nozzle. This phenomenon has previously been found to be particularly important in determining both the OASPL and peak frequency of the broadband high-frequency Shock-Associated Noise (BBSAN) emitted by a given jet configuration. The current work has also illuminated the relationship between cell location and flow characteristics, and thus the effect of jet operating conditions on BBSAN can now be determined. The relationship between cell location and jet breakaway is also under investigation. Predictions are compared with experimental results obtained using flow visualization techniques. This work is in the process of being extended so that the Rankine-Hugoniot conditions can be used to predict the shock cell structure (and thus the BBSAN) along the entire jet.


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Geometrically Nonlinear Free Axisymmetric Vibrations Analysis of Thin Circular Functionally Graded Plates Using Iterative and Explicit Analytical Solution

Rachid El Kaak, Khalid El Bikri and Rhali Benamar


https://doi.org/10.20855/ijav.2016.21.2414


This paper deals with nonlinear free axisymmetric vibrations of functionally graded (FG) thin circular plates whose properties vary in thickness. The inhomogeneity of the plate is characterized by a power law variation of the Young's modulus and mass density of the material along the thickness direction, whereas Poisson's ratio is assumed to be constant. The theoretical model is based on Hamilton's principle and spectral analysis using a basis of admissible Bessel's functions to yield the frequencies of the circular plates under clamped boundary conditions on the basis of the classical plate theory. The large vibration amplitudes problem, reduced to a set of nonlinear algebraic equations, is solved numerically. The nonlinear to linear frequency ratios are presented for various values of the volume fraction index n showing a hardening type nonlinearity. The distribution of the radial bending stresses associated to the nonlinear mode shape is also given for various vibration amplitudes and compared with those predicted by the linear theory. Then, explicit analytical solutions are presented, based on the semi-analytical model previously developed by El Kadiri et al. for beams and rectangular plates. This model allows direct and easy calculation for the first nonlinear axisymmetric mode shape with its associated nonlinear frequencies and nonlinear bending stresses of FG circular plates, which are expected to be very useful in engineering applications and in further analytical developments. An excellent agreement is found with the results obtained by the iterative method.


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Two-Temperature Generalized Thermoelastic Infinite Medium with Cylindrical Cavity Subjected To Time Exponentially Decaying Laser Pulse

Eman A. N. Al-Lehaibi


https://doi.org/10.20855/ijav.2016.21.2415


The present work is devoted to a study of the induced temperature and stress fields in an elastic infinite medium with cylindrical cavity under the purview of two-temperature thermoelasticity. The medium is considered to be an isotropic homogeneous thermoelastic material. The bounding plane surface of the cavity is loaded thermally by time exponentially decaying laser pulse. An exact solution of the problem is obtained in Laplace transform space, and the inversion of Laplace transforms have been carried numerically. The derived expressions are computed numerically for copper, and the results are presented in graphical form.


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