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Published Articles

The Volume 18, No 3, September 2013

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A Novel Viscoelastic Material Modulus Function for Modifying the Golla-Hughes-McTavish Method

Luke A. Martin and Daniel J. Inman


The growing popularity of finite element analysis in the 1980s and 1990s spawned new techniques for modelling damping in complex structures. The Golla-Hughes-McTavish (GHM) method is one technique developed during this era. This method adds non-spatial degrees of freedom to a finite element model in order to account for a viscoelastic material's ability to dissipate energy. In the GHM method, a material modulus function is used to characterize the frequency-dependent complex modulus. This paper presents a novel material modulus function, thus modifying the GHM method. The advantages of this Modified Golla-Hughes-McTavish (MGHM) approach are a reduction in the curve fitting error and a standardized approach for computing material modulus coefficients. An additional parameter is introduced for each dissipation degree of freedom. This paper will compare the original GHM curve fit approach with this new standardized MGHM approach. Advantages of the MGHM approach and physical insight into the model are explained.

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Active Control of Radiated Sound from Stiffened Plates Using IDE-PFC Actuators

Atanu Sahu, Tirtha Banerjee, Arup Guha Niyogi and Partha Bhattacharya


It has been a practice in modern day aircraft and automobile industries to manufacture a stiffened structure for significantly enhancing efficiency and strength without incurring a considerable weight increase. In the present study, an attempt is made to understand the effect of stiffeners on the sound radiation pattern of a vibrating plate. Subsequently, a velocity feedback control algorithm based on Linear Quadratic Regulator (LQR) methodology is developed to attenuate the radiated sound power from the vibrating structures with surface bonded piezo fibre composite (PFC) patches with interdigitated electrodes (IDE) as actuators and polyvinylidene fluoride (PVDF) films as sensors. Results are obtained for different orientations of stiffeners and various locations of PFC patches and are discussed.

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Study of the Effect of the Linear Temperature Behaviour on a Non-Homogeneous Trapezoidal Plate of Parabolically Varying Thickness

A.K.Gupta and Pragati Sharma


An analysis is presented for studying the effect of the linear temperature behaviour on the transverse vibration of a non-homogeneous trapezoidal plate of varying thickness on the basis of classical plate theory. The non- homogeneity of the plate material is assumed to arise due to the variation in density, which is assumed to vary parabolically. The thickness of the plate also varies parabolically. A two-term deflection function is performed to solve the equation of motions using the Rayleigh-Ritz method. The frequency equation is derived when two edges of the plate are simply supported and two are clamped, which is called clamped simply-supported clamped simply- supported. Effects of the non-homogeneity with other plate parameters—such as aspect ratio, taper constant, and thermal gradient on the first two modes of vibration—have been analysed. Results are presented in graphical form.

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Formulation of Weighted Goal Programming Using the Data Analysis Approach for Optimising Vehicle Acoustics Levels

Ahmad Kadri Junoh and Ahmad Kamal Ariffin


Two factors for customers to consider when purchasing a vehicle are the vehicle acoustical comfort and the vi- bration in the vehicle cabin, both of which contribute to a comfortable driving environment. The amount of discomfort is included by frequency, magnitude, direction, and the period during which the noise is experienced and also where the vibration is experienced in the cabin. The main sources of vibration that have been identified previously are the vibration transmitted from engine and the vibration transmitted from the interaction of the tires with the road surface. In this study, we investigate the effect of the vibration caused by the tire interaction with the road surface by estimating the amount of noise produced due to this phenomenon. The methodology focuses on the trends which occur in the noise exposure and on the vibration exposure that has been generated throughout the engine operating rpm range in both stationary and non-stationary conditions. The vibration dose value (VDV)f was used to assess the amount of vibration exposure that is transmitted to the driver's body in the cabin. Through the study, we have proved that the vibration caused by the tire-road surface contact is a major contributor to the cabin's interior noise. Based on the results, a goal programming method was developed to optimise the noise lev- elin the cabin by considering the vibration as an input in the model. Finally, a multi-objective goal programming was developed successfully which could be used to optimize the noise level in the cabin by looking at the value of the VDV required at particular engine speeds (rpm).

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Natural Frequencies and Acoustic Radiation Mode Amplitudes of Laminated Composite Plates Based on the Layerwise FEM

JinWu Wu and LingZhi Huang


In this paper, the natural frequencies and acoustic radiation mode amplitudes of laminated composite plates are studied. The layerwise finite element model is imposed to determine the natural frequencies and velocity distri- butions of laminated composite plates. The amplitude of the laminated composite plates are then discussed based on the acoustic radiation mode, the effects of the panel orientation angle, the elastic modulus ratio, the width- depth ratio, and the damping ratio on the first acoustic radiation mode. A sixteen-layer laminated plate was used as an example, and the numerical simulations and experimental results show that the natural frequencies of the laminated composite plate can be analysed accurately using the proposed model. Furthermore, it is found that the effects of the panel orientation angle and width-depth ratio on the acoustic radiation mode amplitude of the laminated composite plates are significant.

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