Determination of acoustic impedances of multi matching layers for narrowband ultrasonic airborne transducers at frequencies &lt;2.5MHz – Application of a genetic algorithm

Saffar, Saber; Abdullah, Amir

doi:10.1016/j.ultras.2011.08.001

Cited by 26 publications

(6 citation statements)

References 26 publications

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“…The mathematical introduction method applied in Saffar and Abdullah 55 published by the same author which yields to the following equation to link the pressures and particle velocities in both the first and last media:…”

Section: Sound Wave Transmission Through Multilayer Systems Consideri...mentioning

confidence: 99%

Acoustic modeling of honeycomb structures for second load direction with damping consideration

Saffar

2022

Building Acoustics

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The control of low-frequency noise in buildings has become a critical issue because of the inadequate sound insulation in low frequencies (<200 Hz) for most partitions and doors. In the present study, an analytical model has been proposed to specify the relationship between the acoustic parameters such as acoustic impedance of honeycomb and the honeycomb geometry. In this regards, three materials (Polycarbonate, Polypropylene, and Polyurethane), seven angles (45°, 30°, 15°, 0°, −15°, −30°, −45°), and three cell arrangement (1 × 1, 2 × 2, and 3 × 3) were considered to find out the effect of these parameters on the sound absorption coefficient. Sound absorption in the frequency range of 1–500 Hz for angles of 45°, 30°, 15°, 0°, −15°, −30°, −45° was demonstrated using MATLAB software. A comparison of the results showed that the greater the angle’s absolute value, the more the sound absorption coefficient. By comparing all three materials’ absorption coefficient values, it was concluded that the 1 × 1 arrangement had greater absorption than the 2 × 2 and 3 × 3 arrangements. Also, the number of resonance peaks of polyurethane material for all angles was greater than the others in the same frequency range. Then, the panel with the honeycomb core of Polyurethane and 1 × 1 arrangement was recommended for cells with an internal angle of −45° in the present research case study for having more sound absorption.

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Section: Sound Wave Transmission Through Multilayer Systems Consideri...mentioning

confidence: 99%

Acoustic modeling of honeycomb structures for second load direction with damping consideration

Saffar

2022

Building Acoustics

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“…In order to simplify the study, only the motion of particles due to the floor vibration is considered as the main factor for machining, and the acoustic power transmitted to the abrasive particles and workpiece due to high impedance and attenuation is neglected. 47,48 The hybrid FEM/BEM approach is employed to find out the dynamic response of the container floor and its relation to the machinability. This method provides a good understanding of the vibration behavior of the container floor due to the sound source.…”

Section: Experimental Testsmentioning

confidence: 99%

Surface roughness study of polyamide in nano-metric polishing using low-frequency acoustic energy

Beigmoradi

Vahdati

2021

Proceedings of the Institution of Mechanical Engineers, Part B:

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Polymers have gained the attention of manufacturers due to their significant advantages such as low density, high corrosion resistance, and high humidity resistance. Producing high-precision polymeric components is one the most challenging issues especially in fabricating complex or micro-scale systems. Some of the machining techniques such as electro discharge machining (EDM) and electrochemical machining (ECM) cannot be employed for machining the non-conductive parts. Using abrasive particles is one of the best options for machining these types of materials. In this work, the capability of the acoustic energy for machining polyamide (PA) workpieces is studied. To this end, an experimental setup is installed and design of experiment (DoE) algorithm is employed to survey the effect of process parameters on surface roughness. Three parameters at three levels are considered as the effective factors of the process and the sensitivity of the surface roughness on the process factors is investigated. In the next step, a hybrid finite element/boundary element approach was used to discuss the relation of process parameters to the vibrational characteristics of the container, then the mechanism of the process was investigated employing the discrete element method. Finally, the surface topology of the optimal workpiece before and after the process was presented and compared. It was observed that acoustic energy can be considered as a vibration source of the container’s floor to provide kinetic energy for machining PA parts on the nano-metric scale. Moreover, it was found that the initial roughness of the workpiece and the chosen parameters play a crucial role in the machining process. Experimental results show that in this technique by selecting appropriate process factors the surface roughness can be reduced up to 50%.

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“…It is briefly presented in Appendix A. Nevertheless, the design of piezoelectric transducers is still often determined by optimizing the acoustic impedance matching between the piezoelectric material and the tested material [32][33][34][35].…”

Section: External and Embedded Transducersmentioning

confidence: 99%

Design optimization of embedded ultrasonic transducers for concrete structures assessment

Dumoulin

2017

Ultrasonics

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In the last decades, the field of structural health monitoring and damage detection has been intensively explored. Active vibration techniques allow to excite structures at high frequency vibrations which are sensitive to small damage. Piezoelectric PZT transducers are perfect candidates for such testing due to their small size, low cost and large bandwidth. Current ultrasonic systems are based on external piezoelectric transducers which need to be placed on two faces of the concrete specimen. The limited accessibility of in-service structures makes such an arrangement often impractical. An alternative is to embed permanently low-cost transducers inside the structure. Such types of transducers have been applied successfully for the in-situ estimation of the P-wave velocity in fresh concrete, and for crack monitoring. Up to now, the design of such transducers was essentially based on trial and error, or in a few cases, on the limitation of the acoustic impedance mismatch between the PZT and concrete. In the present study, we explore the working principles of embedded piezoelectric transducers which are found to be significantly different from external transducers. One of the major challenges concerning embedded transducers is to produce very low cost transducers. We show that a practical way to achieve this imperative is to consider the radial mode of actuation of bulk PZT elements. This is done by developing a simple finite element model of a piezoelectric transducer embedded in an infinite medium. The model is coupled with a multi-objective genetic algorithm which is used to design specific ultrasonic embedded transducers both for hard and fresh concrete monitoring. The results show the efficiency of the approach and a few designs are proposed which are optimal for hard concrete, fresh concrete, or both, in a given frequency band of interest.

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Determination of acoustic impedances of multi matching layers for narrowband ultrasonic airborne transducers at frequencies <2.5MHz – Application of a genetic algorithm

Cited by 26 publications

References 26 publications

Acoustic modeling of honeycomb structures for second load direction with damping consideration

Acoustic modeling of honeycomb structures for second load direction with damping consideration

Surface roughness study of polyamide in nano-metric polishing using low-frequency acoustic energy

Design optimization of embedded ultrasonic transducers for concrete structures assessment

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