• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1233-1240
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• 1996

Conventional measurement methods using ultrasonic wave or x-ray, eddy current for non-destructive testing(NDT) in nuclear power plants and other industrial plants have been utilized as the method of contact with objects to be inspected. For this reason these methods require relatively much time and inspection area is limited by the location of probe or film. But holograpic interferometry which is a non-contact optical measurement method using a coherent light source has an advantage that quantative measurement can be performed at a time. In this paper a new method using realtime holographic interfreometry and image processing for detecting internal flaws of pressure vessels is presented.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.303-305
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• 2005

Recently, various plastics are used for improvement of reliability and thermal stability of electronic goods. But, it is difficult to choose suitable balance of grade resin to each other product property. Selection of high efficiency resin is becoming inescapable circumstance according to change of reflow temperature of product and development of product following to lead free. Using a inexpensive and reasonable resin, that sustain a uniform performance of product quality. It is make a robust product and increase a company's competitive power. Hereupon, I introduce example that use ESPI methods of thermal deformation analysis of product using in our company product. I try to refer to a structural weak point detection of real time measurement of electronic parts instead of mechanical and chemical measurement of specimen type.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1509-1521
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• 2013

Social demand for the stability of structures lead to the development of the technology to accomplish it. The non-destructive seismic technique, which is able to assess structural integrity of infrastructures, belongs to this category. Seismic technique is focused on the measurement of seismic velocity propagating through the material, and has to utilize sensors coupled to material surface, which does not allow the testing to be performed on the fly. In this paper, a general vocal microphone, which works as a non-contact sensor, was adopted to facilitate seismic testing with mobility and efficiency improved. The target of using microphones was oriented toward quality assessment of compacted subgrade, stiffness evaluation and health monitoring of concrete structures. Experimental parametric study and field applications were performed to investigate reliability and efficiency of microphones. Finally, the optimal test configuration of microphones was suggested for resonance tests and surface-wave tests.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.3-9
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• 2007

With a growing concern about the state of infrastructure worldwide, the demand for the development of reliable nondestructive testing techniques (NDT) is ever increasing. Among possible NDT techniques, microwave method is proven to be effective in fast and non-contact inspection of concrete structures and inclusions inside concrete. It is also found that the microwave method has a potential in detecting the delamination between fiber reinforced polymers (FRP) plate and concrete. On the other hand, ultrasonic method can be another way to find the delamination. In this paper, the research work needed for the development of a reliable microwave method and ultrasonic method is studied in the measurements of concrete specimens reinforced with FRP. Concrete specimens are made with FRP and artificial delamination inside. A microwave measurement system with hom antennas with high center frequency and broad frequency bandwidth are used to image inside concrete specimens for the detection of debonding between concrete and FRP. Also, ultrasonic method is used for the same condition. Both results are compared with each other.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.263-268
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• 2004

In the present study, a Nd;YAG Laser (pulse type) was used to emit ultrasonic signals to a test material. In addition, a total ultrasonic investigation system was designed by adopting a Fabry-Perot interferometer, which receives ultrasonic signals without any contact. For non-destructive test SM45C, which contains some flaws was used as a test material. Because it is easy to align light beam in receiver, and the length of the light beam does not change much even if convex mirror leans towards one side, confocal Fabry-Perot interferometer, which has stable frequency, and PI control are used to correct interfered and unstable signals from temperature, fluctuation and time shift of laser frequency. Stable signals are always obtained by the feedback of PI circuit signals in the confocal Fabry-Perot interferometer. The type, size and position of flaws inside the test material were examined by achieving the stabilization of an interferometer. This study presented a useful method, which could quantitatively investigate the fault of objects by using a Fabry-Perot interferometer.

• Journal of the Korean Magnetics Society
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• v.26 no.1
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• pp.19-23
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• 2016

In this study, we have constructed a measuring system to investigate tensile stress measurement of tendons, which is employed in bridges, by means of the non-destructive and non-contact method. The measuring system consists of tensile stress applying apparatus up to 2 GPa, and power supply for ac and dc current to tendon directly to magnetize tendon in circular direction and to coil wound on yoke to magnetize tendon in axial direction. We have used two kinds of tendon, which were produced by different companies, using the measuring system constructed in this work. Two kinds of experiments are carried out in this work; $1^{st}$ experiment : ac current was applied to the tendon and dc current was applied to coil wound on the yoke, and voltage induced from search coil wound on yoke (SCY) was measured and $2^{nd}$ experiment : dc current was applied to the tendon and ac current was applied to coil wound on the yoke, and voltage induced from search coil on tendon (SCT) was measured. In case of $1^{st}$ experiment, voltage induced from SCY was changed below 200MPa tensile stress but the voltage was not increased above 200 MPa. In case of $2^{nd}$ experiment, voltage induced from SCT was decreased up to 1.5 GPa linearly. We expect that $2^{nd}$ experiment could be applied to the non-destructive testing of tensile stress measurement of tendon.