• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.256-256
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• 2003

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.270-275
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• 2013

In this study, focusing of ultrasonic Lamb wave by negative refraction with mode conversion from antisymmetric to symmetric mode was investigated. When a wave propagates backward by negative refraction, the energy flux is antiparallel to the phase velocity. Backward propagation of Lamb wave is quite well known, but the behavior of backward Lamb wave at an interface has rarely been investigated. A pin-type transducer is used to detect Lamb wave propagating on a steel plate with a step change in thickness. Conversion from forward to backward propagating mode leads to negative refraction and thus wave focusing. By comparing the amplitudes of received Lamb waves at a specific frequency measured at different distance between transmitter and interface, the focusing of Lamb wave due to negative refraction was confirmed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.792-796
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• 2006

In recent years, the semiconductor industry and the optical industry is developed rapidly. The recent demand has expanded for optical components such as a optical lens, a optical semiconductor and a measuring instrument. Object transport systems are driven typically by the magnetic field and the conveyer belt. Recent industry requires more faster and efficient transport system. However, conventional transport systems are not adequate for transportation of optical elements and semiconductors. Because conveyor belts can damage precision optical elements by the contact force and magnetic systems can destroy the inner structure of semiconductor by the magnetic field. In this paper, the levitation transport system using ultrasonic wave is developed for transporting precision elements without damages. This transport system is using 2-mode ultrasonic wave excitation and flexural beam modes shapes are evaluated. It compared simulation results with experimental results

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.45-51
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• 2015

An experimental study was performed for the analysis of frequency-equivalence ratio correlation in the methane-air premixed flame influenced by ultrasonic standing wave. The propagating flame was caught by high-speed Schlieren photography, and the variation of flame-behavior including the flame structure was investigated in detail employing a post-processing analysis of the high-speed images. It was found that a structural variation and propagation-velocity augmentation of the methane-air premixed flame by the intervention of ultrasonic standing wave were more caused off around the stoichiometry. Also, a dependency of the flame behaviors on the driving frequency and equivalence ratio of the reactants was confirmed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.123-127
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• 1997

Recently, it is gradually raised necessity that interface is measured accurately and managed in industrial circles and medical world, An Ultrasonic wave transmitted from a focused beam transducer is being expected as a powerful tool for NDE of micro-defect. The ultrasonic NDE of the defect is based on the form of the wave reflected form the interface In this study, regarding to the thickness of film which is in opaque object and thickness measurement was done by MEM-cepstrum analysis of received ultrasonic wave. In measument results, film thickness which is beyond distance resolution capacity was measured accurately. Also, automatically repeated discrimination analysis method can be decided in the category of all kinds of defects on semiconductor package.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.835-838
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• 2002

A running high voltage equipments produce ultrasonic wave that has unique sound by the specific characteristics of the electricity. The generation of the ultrasonic wave is made by the electric transform like arcing, corona, and tracking so on. The mechanical losses and fatal human damages are happened by the electric failure of high voltage equipments. To prevent and diagnose the obstacle factors of the high voltage equipments, the measurement of the ultrasonic wave became to be prominent. However standardized data have been a deficient situation by now. This paper measures the ultrasonic wave coming from the real running transformer equipments and transforms it as an audio frequency. Measured data represents as frequency and time domain through the FFT(Fast Fourier Transform) transform. In conclusion, the purpose of this paper is to standardize the analyzed data.

• Korean Journal of Materials Research
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• v.16 no.11
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• pp.687-691
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• 2006

Synthesis of Iron oxides by air oxidation of $FeSO_4$ solutions in the presence of NaOH, Diethylenetriamine (DETA), Butylamine (BA) and influence of ultrasonic wave were investigated by XRD, SEM and particle size analyzer. As the DETA addition increased to 0.05 mol, $Fe_3O_4$ was formed with goethite($\alpha$- FeOOH) and $Fe_3O_4$ single phase was formed above 0.18mol of DETA. As the BA addition increased, the XRD peak intensity of (020) face of lepidocrocite($\gamma$-FeOOH) was developed until the formation of $Fe_3O_4$ and reduced the size of the iron oxide particles formed. Ultrasonic wave reduced the size of the iron oxide particles but gave little effects on the iron oxide particles synthesized by amine.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.1
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• pp.9-17
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• 2016

The elastic modulus of a 3D-printed Kelvin foam plate is investigated by measuring the acoustic wave velocity of 1 MHz ultrasound. An isotropic tetrakaidecahedron foam with 3 mm unit cell is designed and printed layer upon layer to fabricate a Kelvin foam plate of 14 mm thickness with a 3D CAD/printer using ABS plastic. The Kelvin foam plate is completely filled with paraffin wax for impedance matching, so that the acoustic wave may propagate through the porous foam plate. The acoustic wave velocity of the foam plate is measured using the time-of-flight (TOF) method and is used to calculate the elastic modulus of the Kelvin foam plate based on acousto-elasticity. Finite element method (FEM) and micromechanics is applied to the Kelvin foam plate to calculate the theoretical elastic modulus using a non-isotropic tetrakaidecahedron model. The predicted elastic modulus of the Kelvin foam plate from FEM and micromechanics model is similar, which is only 3-4% of the bulk material. The experimental value of the elastic modulus from the ultrasonic method is approximately twice as that of the numerical and theoretical methods because of the flexural deformation of the cell edges neglected in the ultrasonic method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.207-208
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• 2021

The non-destructive method using ultrasonic waves has been applied in many studies due to its low damage to the structure and its simple evaluation method and high precision. On the other hand, if the concrete is subjected to a high-temperature, the mechanical properties may be deteriorated due to the micro-crack network and the damage may be severe depending on the strength of the concrete. Therefore, this study attempts to evaluate the fundamental wave behavior of different strength ranges using the ultrasonic non-destructive method for concrete that has been subjected to high-temperature. As a result, the relative power of the fundamental wave was decreased as temperature increase. And it was confirmed that the 2nd and 3rd harmonics were generated at 110 MPa. However, to check the 2nd, 3rd harmonics 110 MPa or less, there is a need for further research considering the ultrasonic output, the output of the sender and receiver, and the appropriate frequency accordingly.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.38-45
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• 2004

Ultrasonic signals transmitted through adhesively bonded plates were used to evaluate parameters related to attenuation and frequency in the adhesively bonded joint. The kinds of bonding materials with a different bonding thickness of constant pressure were used. And ultrasonic diagnosis was evaluated by p-wave sensor of 10MHz. FFT has been performed to determine bond-layer parameters such as effective thickness and frequency for adhesively bonded joint of A16061 plates in comparison with measured to theoretical ratios. When variable thickness exists, the ultrasonic spectrum was changed the frequency wave. The more materials thickness and the higher the frequency, the larger shift was observed. Measured ratios for cases of bond thickness and variety bonding materials are then used to determine bond parameters. The results show that the technique can be applied to the characterization of adhesively bonded joint.