• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.131-132
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• 2008

This paper describes a method to estimate the thermal lifetime of coil used in the dry-type molded transformer which is widely used in the domestic distribution system. In order to reduce the testing time, temperature accelerated aging test is planned. Finally, the thermal lifetime estimation method is composed of a temperature aging test and a cyclic test of temperature, humidly and lightning impulse voltage withstand test.

• Journal of Applied Reliability
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• v.12 no.3
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• pp.177-186
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• 2012

This paper presents a comparison of the failure mechanism for high power converted white LEDs(3W) with the commercially available YAG:Ce and silicate phosphor. We carry out the normal aging life test for 10,000 hours, the high temperature aging test for 8,000 hours, the high temperature and humidity aging test for 8,000 hours and the current aging testing for 5,000 hours. The optical and electrical parameters of LEDs were monitored, such as lumen, correlated color temperature (CCT), chromaticity coordinates(x, y), thermal resistance, I -V curve and spectrum intensity. The stress induced a luminous flux decay on LED in all experiments and causes a failure. So we try to find out what's a main failure mechanism for a high power LED.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.403-406
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• 2009

This research is based on the altitude temperature, pressure and humidity, as defined by MIL-HDBK-310 standard and modifies this conditions to conform to the new standard MIL-STD-810F and test procedure given in AIAA-2466 from this fundamental guideline optimal design and sizing of test section, inlet, exhauster duct, temperature and humidity control was performed.

• Journal of Korean Society for Quality Management
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• v.25 no.1
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• pp.135-141
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• 1997

The Copper-Clad Laminate (CCL) is a main electronic component of specialtype printed circuit boards (PCBs) such as Silver Through Hole PCB. This CCL should have high reliability under the aging test, and usually the test is done at a higher temperature (110-$150^{\circ}C$) than the normal. Then, this test condition of high temperature may cause such quality problems as hole eccentricity and reduction of distance between part holes. After measuring the CCL shrinkage affected by temperature, the correction factor of a press mold was a, pp.ied to solve these problems. The results showed that the tolerance of hole pitch(${\pm}$$100{\mu}m$) was satisfactory and the internal and external failure costs were reduced by 55%.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.109-115
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• 2006

This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$, Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1644-1650
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• 2001

Mechanical properties of domestic 374 stainless steel have been evaluated fur membrane material used in LNG storage tank. LNG tank is operated around -162$^{\circ}C$. The temperature of membrane depends on LNG level. Accordingly, the membrane material is deteriorated by variation of liquid pressure and temperature. Tensile test and fatigue life test were performed at room temperature and -l62$^{\circ}C$ per code requirements. Especially the biaxial fatigue life test was conducted with shaped membrane sheet at a thermal strain of $\Delta$T=190$^{\circ}C$ The test results obtained with the domestic 304 stainless steel showed better properties compared to the values required by code.

• Journal of Applied Reliability
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• v.9 no.4
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• pp.319-329
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• 2009

The airbag module is an inflatable restraint system that inflates within 0.05 seconds automatically in a collision to protect the occupants. The airbag fabrics used in the module are required to have the good resilience and strength and also to have retained at least 80% of mechanical properties after using longer than 10 years. In this study, we develop an accelerated test method in order to predict the lifetimes of airbag. In this test, we select temperature and humidity as environmental stresses by analyzing the failure mechanisms of coated and uncoated nylon 66 fabrics. It is found that the degradation of airbag fabrics is effectively accelerated under the combined conditions of high temperature and humidity. Analyzing the results of the accelerated test, the lifetimes of airbag fabrics are predicted to be longer than 10 years.

• Journal of Applied Reliability
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• v.2 no.1
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• pp.15-22
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• 2002

This paper is concerned about an Accelerated Life Test for Micro Display Device which is being used in a Projection TV, in order to find a failure mode occurred in field in a short time, to identify a major factor to affect a life, and to estimate a mean life. For this purpose, we selected a temperature as a accelerated factor to perform a test and measured degradation of display device using visual inspection and chromaticity table. In the result of Accelerated Life Test, it is confirmed that failure mode is equal to the degradation of display device by vendor and the Temperature is a major factor to affect a failure. Besides, according as the display device is turned to green as degraded, it is identified that the change of the chromaticity value is one method to measure the degree of the degradation . So, we applied the optimal condition, which consider a cost and life to lower the Temperature which is a major factor acquired by the result of ALT, to PTV design

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.596-598
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• 2000

This paper presents a new accelerating aging test facility for distribution lightning arresters. Aging parameters of lightning arrester are moisture ingress, electrical stress and surge absorption and so on. In this system, we applied 13.2kV to 6 samples and controled temperature and humidity of chamber and measured leakage currents of the all samples. Also we developed accelerating aging cycle which consists of -35$^{\circ}C$∼90$^{\circ}C$ temperature and 40%∼90% humidity. Through the aging test we found out the leakage current of aged sample increases rapidly according to the temperature rising. Hereafter we can determine the replacement guide of leakage current for field operating arresters and condition assessment of aged samples through this aging test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.1012-1015
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• 2005

This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$. Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.