• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.503-504
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• 2006

This paper describes a low-level partial discharge(PD) testing that has been accepted as a non-destructive test method on insulation performance of electronic components. A comparative PD analysis combined with the Withstand Voltage Test (WVT) specified in IEC standards is carried out on high frequency switching transformers. The analysis shows that insulation degradation of the transformers under test progresses during the WVT. To avoid insulation degradation of the specimen, PD test has to be carried out at as low voltage as possible. In this study, the PD test on the transformers is performed in ranges from 50% to 70% of the test voltage specified in the WVT by measuring apparent charges below 1 pC. From the experimental results, it is expects that the low-level PD test is applicable for electronic components as a replacement of the WVT.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.1
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• pp.41-47
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• 1984

Increase of the requirements on quality of welded structures necessitates the improvement of known inspection methods and the introduction of progressive new techniques. Non-destructive methods are the most advanced, but there are considerable difficulties in using the methods of radiography with electromagnetic rays and ultrasonic testing in the inspection of dissimilar metal friction welds, because their physical and mechanical properties are changed very rapidly at the interface. The values of simple mechanical test for dissimilar metal friction welds have always been dubious, as the strength of the bond is often greater than that of the softer materials being jointed. Thus, in this paper some conventional mechanical testing methods are examined in an attempt to determine a technique for dissimilar metal friction welds, which will give a reliable quantitative indication of the weld quality. From the considered static and dynamic testing methods the impact bending test on unnotched and notched specimens are the most sensitive to find out the small joining defects in the interface.

• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.239-244
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• 2001

Today, Ultrasonic is used as an important non-destructive test tool of semiconductor reliability evaluation and failure analysis. The semiconductor packaging trend goes to develop thin package, this trend makes difficult to inspect to defect in semiconductor package. One of the important problem in all semiconductor is moisture absorption in the atmosphere. This moisture causes crack or delamination to package when the semiconductor package is soldered on PCB. Reliability evaluation of semiconductor's object is investigating the effect of this moisture. For that reason, this study is investigating the effect of this moisture and reliability evaluation of semiconductor after preconditioning test and scanning acoustic microscope.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.497-519
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• 2003

Science and technology is an essential ingredient of the progress in modern society. Measurements enable action and actions enable results. Non-Destructive Evaluation (NDE) - the science and technology of measurements without affecting the Properties and performance of the test object is an interdisciplinary domain area of high significance far ensuring quality, productivity and safety thus enabling better qualify of lift to the inhabitants on this planet. The test object can be material, component, plant, earth, environment etc. Total qualify management, total productivity management, concurrent engineering and many other essential ingredients of success in plant engineering and manufacturing industry are dependent on NDE far success and good returns on investments.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1574-1575
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• 2011

The application of a pulsed power system is being extended to an environmental and industrial field. The non-destructive gaseous pollutants from industrial plants such as power generation plants and incinerators can be processed by applying high voltage pulses with a fast rising time (a few nanoseconds) and short duration (nano to microseconds) in a pulsed corona discharge reactor. The pulsed plasma generator with a triggered switch has been developed. Its corona current in load can be adjusted by applied voltage and repetition rate. We investigated the performance of the pulsed plasma generator by analyzing the concentration of ozone in small reactor. This paper describes the electrical characteristics of the pulse generator with a voltage of 30 kV at repetition rate of 50 PPS. In addition, we briefly discuss a configuration of the system and initial test results.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.72-74
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• 2006

The application of the variable polarity plasma arc welding process to A12219 is described. The thickness of aluminum alloy is 11.45mm and 5.08mm. 1-pass keyhole welding is applied to butt welding and 2-pass welding is also applied to thick material. During welding, all welding parameters are controlled by automated system and acquired by 10kHz rate. This paper covers the welding parameters, result of non-destructive test and tensile test.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1712-1714
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• 2001

This paper deals with the development and application of an inner corrosion detector for the ACSR(Aluminum Conductor Steel Reinforced) power lines. The detector runs on an ACSR power line and inspects the inner corrosion of the conductor using the technology of the nondestructive eddy current test. It is consists of an ECT sensor, signal processing units, a RF transmitter/receiver, and etc.. The experimental result through field tests shows the detector can efficiently find both the zinc and aluminum loss of ACSR power lines.

• Journal of Korea Foundry Society
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• v.18 no.3
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• pp.254-261
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• 1998

Microstructure and mechanical properties of the low pressure die-cast Al wheels were investigated by microscope, image analyzer, NDT (non-destructive test), and tensile test. The variation of SDAS (secondary dendrite arm spacing), porosity per unit area, quality grade, and tensile properties with the mold temperatures were examined. SDAS was gradually decreased with a decrease in temperature. However, the lowest value of porosity per unit area was observed at the mold temperature of $405^{\circ}C$ and the optimum mold temperature was found to be $405^{\circ}C$. Besides, from the observation of pore morphology, it was also found that the pore formation was mainly caused by shrinkage during solidification. The tensile strength, elongation, and impact toughness were markedly decreased, however the yield strength was nearly constant. The decrease of mechanical properties is attributed to the increase of porosity.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.327-329
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• 2004

Reliability evaluation of the welded structure for industrial structures/facilities such as power plant and petro-chemical refinery facilities is very important, and especially the reliability diagnosis of the structure is based on the exact evaluation of materials properties. But, the conventional Pre-Qualification test had the difficulty of evaluating the real material properties in the field because the test was made on the specimen with the simulated welding for the in-field welding condition. Therefore, a continuous indentation technique was proposed for simple and non-destructive testing of in-field structures and for selective testing of local range such as heat affected zone and weldment.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1887-1891
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• 2008

In this paper, we dealt with a partial discharge (PD) measurement method that has been accepted as an effective and non-destructive technique to estimate insulation performance of low-voltage induction motors. The PD measurement system consists of a coupling network, a low noise amplifier, and associated electronics. A shielded box was used to reduce environmental noise. Frequency characteristic of the coupling network was estimated by a sinusoidal signal input, and the low cut-off frequency of the coupling network was 1 MHz (-3 dB). Also, we carried out a calibration test for the PD measurement system. Sensitivity of the system was of 84 m$V_{max}$/pC between stator winding and enclosure. In application test on a low-voltage three phase induction motor (5 HP), we could detect 88 pC at AC 800 $V_{max}$.