• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.364-367
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• 2008

Finite element model and the basic experimental method have been developed to help the design of the transverse ultrasonic horn for flip-chip bonding. With two types of design the horn performance and ultrasonic characteristics are verified by using laser vibrometer. These analysis and experiment results can be the fundamental data for ultrasonic horn design considering the vibration modes and performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.759-763
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• 2015

The laser machining process has been proposed as an advanced process for the selective fabrication of electrodes without a mask. In this study, we adapt laser machining to metals that have different thermal properties. Based on the results, the metals exhibit a different surface morphology, heat-affected zone (HAZ), and a recast layer around the machined surface according to their thermal conductivity, boiling point, and thermal diffusivity. Then, we apply ultrasonic-assisted laser machining to remove the recast layer. The ultrasonic-assisted laser machining exhibits a better surface quality in metals with higher diffusivity than those having lower diffusivity.

• Clean Technology
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• v.17 no.2
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• pp.117-123
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• 2011

In this study, evaluation tests for cleaning performance of various cleaning agents and selection of optimal ultrasonic cleaning parameters were executed to develop an efficient cleaning process in remanufacturing of laser copy machine. Cleaning performance tests were executed with 8 cleaning agents (A~H) to remove the contaminants of oil-ink, toner particles, and shoe polish. Physical properties and foamability tests were also applied. For 3 types of contaminants, cleaning agent G showed superior cleaning performance compared to agent A which has being used at a remanufacturing of laser copy machine in Korea. With cleaning agents selected in pre-tests, ultrasonic cleaning tests were executed to remove real contaminants on the parts of used digital laser copy machine parts. Cleaning agent G at 28 kHz ultrasonic frequency showed faster cleaning performance compared to agent A and other frequencies. The productivity and economic efficiency in remanufacturing of laser copy machine are expected to increase by adapting agent G and 28 kHz frequency at ultrasonic cleaning process.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.467-475
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• 2016

Ultrasonic propagation imaging (UPI) has shown great potential for detection of impairments in complex structures and can be used in wide range of non-destructive evaluation and structural health monitoring applications. The software implementation of such algorithms showed a tendency in time-consumption with increment in scan area because the processor shares its resources with a number of programs running at the same time. This issue was addressed by using field programmable gate arrays (FPGA) that is a dedicated processing solution and used for high speed signal processing algorithms. For this purpose, we need an independent and flexible block of logic which can be used with continuously evolvable hardware based on FPGA. In this paper, we developed an FPGA-based ultrasonic propagation imaging system, where FPGA functions for both data acquisition system and real-time ultrasonic signal processing. The developed UPI system using FPGA board provides better cost-effectiveness and resolution than digitizers, and much faster signal processing time than CPU which was tested using basic ultrasonic propagation algorithms such as ultrasonic wave propagation imaging and multi-directional adjacent wave subtraction. Finally, a comparison of results for processing time between a CPU-based UPI system and the novel FPGA-based system were presented to justify the objective of this research.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.353-354
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• 2012

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.1
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• pp.7-12
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• 2017

A nonlinear ultrasonic parameter is defined by the ratio of displacement amplitude of the fundamental frequency component to that of the second-order harmonic frequency component. In this study, the ultrasonic displacement amplitude of an SUS316 specimen was measured via a piezo-electric-based method to identify the validity of piezo-electric detection method. For comparison, the ultrasonic displacement was also determined via a laser-based Fabry-Pérot interferometer. The experimental results for both measurements were in good agreement. Additionally, the stability of the repeated test results from the piezo-electric method exceeded that of the laser-interferometric method. This result indicated that the piezo-electric detection method can be utilized to measure a nonlinear ultrasonic parameter due to its excellent stability although it involves a complicated process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.375-376
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• 2008

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.6
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• pp.459-466
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• 2005

The scanning laser source (SLS) technique has been proposed recently as an effective way to investigate small surface-breaking defects, By monitoring the amplitude and frequency changes of the ultrasound generated as the SLS scans over a defect, the SLS technique has provided enhanced signal-to-noise performance compared to the traditional pitch-catch or pulse-echo ultrasonic methods, An extension of the SLS approach to map defects in microdevices is proposed by bringing both the generator and the receiver to the near-field scattering region of the defects, To facilitate near-field ultrasound measurement, silicon microcantilever probes are fabricated using microfabrication technique and their acoustical characteristics are investigated, Then, both the laser-generated ultrasonic source and the microcantilever probe are used to monitor near-field scattering by a surface-breaking defect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.550-554
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• 2014

Regarding thin films in MEMS/NEMS structures, the exact evaluation of mechanical properties is very essential to enhance the reliability of their design and manufacturing. However, such methods as a tensile test and a resonance test, general methods to measure elastic moduli, cannot be applied to thin films since its thickness is so small. This work concerns guided wave based elastic modulus measurement method. To this end, guided wave excitation and detection system using a pulsed laser and a laser interferometry has been established. Also an elastic modulus extraction algorithm from the measured guided wave signal was developed. Finally, it was applied to actual thin film structures such as Ni-Si and Al-Si multilayers. From experimental results, we confirm that the proposed method has considerable feasibility to measure elastic properties of thin films.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.13-18
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• 2016

Toshiba has developed a laser peening system for PWRs(pressurized water reactors) as well after the one for BWRs(boiling water reactors), and applied it for BMI(bottom-mounted instrumentation) nozzles, core deluge line nozzles and primary water inlet nozzles of Ikata Unit 1 and 2 of Shikoku Electric Power Company since 2004, which are Japanese operating PWR power plants. Laser pulses were delivered through twin optical fibers and irradiated on two portions in parallel to reduce operation time. For BMI nozzles, we developed a tiny irradiation head for small tubes and we peened the inner surface around J-groove welds after laser ultrasonic testing (LUT) as the remote inspection, and we peened the outer surface and the weld for Ikata Unit 2 supplementary. For core deluge line nozzles and primary water inlet nozzles, we peened the inner surface of the dissimilar metal welding, which is of nickel base alloy, joining a safe end and a low alloy metal nozzle. In this paper, the development and the actual application of the laser peening system for PWR power plants will be described.