• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.393-397
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramics element as a driving element. That is, L$_1$-B$_4$ linear ultrasonic motor can be constructed using a multi-mode vibrator of longitudinal and bending modes. The simulation with variation of material characteristics of piezoceramic were performed as use of finite element analysis ANSYS 5.5, such as elastic compliance, piezoelectric constant, electro-mechanical coupling coefficient, poisson's ratio and density. The results of simulation, elastic compliance constant s$_{11}$ and piezoelectric constant d$_{31}$ had the most of influence on the elliptic-motion. This results consist with using transverse effect of material. The used motor were piezoceramics of 4 layers, and the dimensions were 65$\times$5$\times$3.5mm(LxWxt).).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.8
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• pp.658-663
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• 1998

Ferrite plating enables were grown by ferrite by plating method in solution at low temperature(<10$0^{\circ}C$). This faciltates the fabrication of new ferrite thin film devices using non- heat-resistant materials(plastic, GaAs ect) as substrates. Combining the ferrite plating with sonochemistry, application of power ultrasonic waves to stimulate chemical reactions, the crystallinity and qualities of films were improved. Modifying the reactions cell and plating conditions further improved the film quality.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1882-1891
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• 2001

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat flux boundary conditions unlike many of the previous researches adopted constant wall temperature conditions. Therefore, in the present study, modified dimensionless parameters such as Ste* and Ra* were used. Also, general relationships between melting with ultrasonic vibrations and melting without ultrasonic vibrations were established during the melting of PCM. Experimental observations show that the effect of ultrasonic vibrations on heat transfer is very important throughout the melting process. The results of the present study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They enhance the melting process as much as 2.5 tildes, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, various time-wise dimensionless numbers provide conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1798-1803
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• 2003

Surface and edge finishing processes are important technological operations of in parts machining. Quality of the finished parts directly affect the performance of the whole product. Especially, edge quality, which depends on burr control, is extremely important. Burrs are undesirable projections of the material beyond the edge of the workpiece. A number of deburring processes have been developed such as barreling, brushing, chemical methods etc. But, there are only few publications in the area of applying ultrasonics to deburring. When ultrasonic vibration propagates in the liquid medium, a large number of bubbles are formed. These bubbles generate an extremely strong force, which can be used to remove burrs. Cavitation is used as a term to describe the erosion of parts caused by the action of cavities in liquid. The object of this study is to analyze the effects of ultrasonic cavitation in the deburring process. For this purpose, we introduce a new ultrasonic cavitation method, which efficiently removes the burrs. Experimental parameters to verify the deburring effects of ultrasonic cavitations are ultrasonic power, amplitude, distant of the transducer from the workpiece, deburring time and abrasive. It has been shown that deburring with ultrasonic cavitation in water is effective to burrs.

• Journal of Conservation Science
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• v.31 no.3
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• pp.267-278
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• 2015

In this study, the elastomer cover, a new contact material, was developed to establish the customized ultrasonic measurement considering surface irregularities of stone cultural heritages. The cover exhibits high elastic force and wear resistance because it has tensile strength of 17MPa and elongation of 625%. In addition, as a result of comparative experiments for the seven types according to transducers and contact materials including the elastomer cover, rock surface irregularities significantly affect attenuation of ultrasonic velocity. The phenomenon was more noticeable in the chiseling finish and indirect transmission measurement rather than the dabbed finish and direct transmission measurement. However, the Type F using the exponential transducer and elastomer cover showed stable P-wave velocity and high amplitude regardless of the surface irregularities. This because the elastomer cover sufficiently sticks to surface irregularities and removes pores between a transducer and a rock specimen. Therefore, the Type F should be used for the ultrasonic measurement of stone cultural heritages with surface irregularities.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.235-241
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• 2009

Composite wood materials are very sensitive to water and inspection without any coupling medium of a liquid is really needed to wood materials due to the permeation of coupling medium such as water. However, air-coupled ultrasound has obvious advantages over water-coupled experimentation compared with conventional C-scanner. In this work, it is desirable to perform contact-less nondestructive evaluation to assess wood material homogeneity. A wood material was nondestructively characterized with non-contact and contact modes to measure ultrasonic velocity using automated data acquisition software. We have utilized a proposed peak-delay measurement method. Also through transmission mode was performed because of the main limitation for air-coupled transducers, which is the acoustic impedance mismatch between most materials and air. The variation of ultrasonic velocity was found to be somewhat difference due to air-coupled limitations over conventional scan images. However, conventional C-scan images are well agreed with increasing the resin-infiltrated time as expected. Finally, we have developed a measurement system of an ultrasonic velocity based on data acquisition software for obtaining ultrasonic quantitative data for correlation with C-scan images.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.20-25
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• 2013

Ultrasonic methods are widely used to degradation assessment. Remaining-life cycle of metal can be estimated by ultrasonic parameters because ultrasonic velocity and attenuation are affected by change of material properties with accumulated fatigue in the metal. Therefore, in this study, we will estimate overall change of material properties by 2D C-scan image. Fatigued aluminum alloy 6061-T6 samples from 0 to 85% were prepared for evaluating fatigue life cycle. Also, degraded image of materials using attenuation is proposed to estimate degree of material degradation for determining degraded area of fatigued samples. Finally, we will predicts process pf degradation with measured attenuation of fatigued aluminum alloy 6061-T6 samples.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.313-320
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• 2007

Recently, a new class of single-crystal piezoelectric materials such as lead metanibobate doped with lead titanate (PMN-PT) has been synthesized and were found to further enhance the electro-mechanical coupling factor compared to piezo-ceramic materials. This paper describes fabrication and evaluation of PMN-PT single crystal ultrasonic transducers for contact measurement of stainless steel that is one of the highly attenuative materials. The design conditions for ultrasonic transducer such as front matching layer between test materials and piezo-material and backing materials were investigated based on the simulation results by KLM model. The PMN-PT single crystal ultrasonic transducers with centre frequencies at 1 and 2.25 MHz were fabricated and their performances were evaluated.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.1
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• pp.69-76
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• 1989

Piezoelectric elements, backing and shoe material are the important components of the ultrasonic transducer. In this study, characteristic constants in the domestic and the foreign PZT ceramic elements are investigated, The acoustic properties of the domestic and the foreign backing and shoes are characterized. The effects of components characteristics, the kinds of the piezoelectric elements and the thickness of the wear plates are investigated for the manufactured normal beam ultrasonic transducers.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.519-524
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• 2009

This work presents a simple technique to determine the Poisson's ratio of homogeneous solid material using a pair of low cost PVDF ultrasonic transducers. It is based on transducer's property of generating longitudinal and transversal waves depending on the excitation frequency. Mechanical tests were conducted to validate the proposed method, resulting in a good agreement between ultrasonic and mechanical techniques.