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Published Articles

The Volume 16, No 2, June 2011

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Optimum Design of a Tuneable Vibration Absorber with Variable Position to Suppress Vibration of a Cantilever Plate

Hamed Moradi, Mojtaba Sadighi and Firooz Bakhtiari-Nejad


Tuneable vibration absorbers (TVAs) are used as semi-active controllers to reduce the undesirable vibrations in applications such as electrical transmission lines, machining processes, gas turbines, engines, and bridges. In this paper, the application of a TVA to suppress vibration of a cantilever plate is presented. The TVA, including mass, spring, and damper elements, is attached to the cantilever plate under harmonic excitation. In addition, the effect of the spring mass is considered in this analysis, which cannot be neglected in the small-scale problems. After the formulation of the problem, the optimum specifications of the absorber, including the spring stiffness and its position, are determined using an algorithm based on mode summation method. Using a numerical algorithm, the spring stiffness of the absorber and its best position are found for different values of excitation force position and frequency.

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New Mathematical Model to Estimate Road Traffic Noise in View of the Appearance Rate of Heavy Vehicles

Mitsunobu Maruyama, Kazuhiro Kuno, Toshio Sone


A new mathematical model is proposed to estimate road traffic noise at sites along a freeway where the traffic volume fluctuates from a maximum of 900 vehicles per hour in the daytime to a minimum of 300 vehicles per hour at night. The model considers traffic conditions such as the percentage of heavy vehicles, time interval between successive (two or more) heavy vehicles and measurement time interval. The A-weighted equivalent continuous sound pressure levels calculated from this model are in keeping with measured ones at several representative time intervals both in the daytime and nighttime.

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Vibration of Visco-elastic Orthotropic Parallelogram Plate with Linear Thickness Variation in Both Directions

Arun Kumar Gupta, Amit Kumar, Harvinder Kaur


A simple model presented here for vibration of a visco-elastic, orthotropic parallelogram plate with linear thickness variation in both directions. Using the separation of variables method, the governing differential equation has been solved for the vibration of a visco-elastic, orthotropic parallelogram plate having clamped boundary conditions on all four of the edges. An approximate but convenient frequency equation is derived by using the Rayleigh-Ritz technique with a two-term deflection function. The time period and deflection function at different points for the first two modes of vibration are calculated for various values of taper constants, aspect ratio and skew angle.

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Hydrodynamics study of group A/B particles in presence of an acoustic filed

Akash Langde, D. J. Tidke, R.L.Sonolikar


The difficulty of putting fine powders in suspension in the fluidized bed is due to cohesiveness and physical forces of attraction between the particles. But fluidization of group A/B particles is not difficult. It fluidized very easily. Motivation of this topic occurred from literature survey. It was found that study was done for all types of fine powder except group A/B boundary particles. In this research work an attempt has been made to improve the flowability of such type of particles acoustic energy excitation. Beside this, effect of an acoustic field on minimum fluidization velocity (Umf) has been found out with variation of frequency and sound pressure level. The Micro fumed silica powder (dp =112?m) was used as fluidizing material. The value of Umfs at 145dB was found out to be 0.44cm/s, which was very less compared to Umfo ?at without sound intensity i.e.1.1cm/s for L/D=0.58.It was also seen that bed expansion (H) was improved with bubble free fluidization compared to in absence of acoustic field. An attempt has been made to train the Artificial Neural Network (ANN) with fluidization data using MATLAB software.

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Effects of Inter-Subject Variability and Vibration Magnitude on Vibration Transmission to Head during Exposure to Whole-Body Vertical Vibration

M. Desta, V.H. Saran, S.P. Harsha*


In this paper, the effect of inter-subject and intra-subject variabilities on transmission of vibration through seated human subjects is discussed using experimental results. The experimental study targeted three representative pos- tures (backrest, erect, and forward lean on table) while performing sedentary activities and under three magnitudes (0.4, 0.8, 1.2 m/s2 rms) of vertical vibration. The frequency range considered is 1 Hz–20 Hz as representative of those likely prevailing in wide range of vehicles. The data sets are investigated in terms of STH (seat-to-head) and BTH (back support-to-head) transmissibilities and phase differences, and respective coherences under the magni- tudes and postures undertaken. In addition to determining the effect of different frequencies, subjective readings were collected at vertical backrest support postures at representative frequencies using the Borg CR 10 comfort scale. The responses show significant variations in transmissibility and phase among all of the subjects. In all pos- tures, the mean STH transmissibility increases with increasing vibration magnitude at body resonance frequency, which lies approximately between 4.5 Hz and 6 Hz. Resonance in STH transmissibility of erect and forward lean on table posture visibly tends to shift to a lower frequency with increasing vibration magnitude. The subjective reading obtained, in terms of discomfort level, match with experimental data sets and provides evidence that human body resonance frequency or discomfort zone is around 5 Hz. Therefore, it might be concluded that the inclusion of vibration magnitude, posture, and inter-subject variabilities in the prediction of seat biodynamic response is es- sential. The development of biodynamic models and design of seat should include the variation of STH and BTH transmissibility and phase in different possible postures under different vibration magnitude.

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Technical Note: Effects Due to Exhaust and Tail Pipes on Insertion Loss of Mufflers

B. Rajavel and M. G. Prasad


In this study, the influence of exhaust pipe lengths on insertion loss(IL) which has not been analyzed in previous studies is investigated. IL is calculated analytically for a simple expansion chamber including source impedance, exhaust and tail pipe lengths. The prediction of frequencies based on models of quarter wave tube and half wave tube for exhaust and tail pipe resonances agree well with the effects seen in experimentally measured IL.

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