• 한국신뢰성학회지:신뢰성응용연구
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• 제16권4호
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• pp.331-337
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• 2016

Purpose: The purpose of this study is the analysis of the failure mechanisms effect of circuit design characteristics of the ballast for LED Lamp Methods: Recently, electronic circuit of ballasts for LED lamp are being occurred on various failure mechanisms (whiskers, ion migration, heat dissipation problem, switching element damage) because electronic ballast circuit design characteristics are becoming more and more diverse. Results: we analysis failure mechanisms that occurs in accordance with the circuit design characteristics The ballast for LED lamp were divided into three different types (Type A, Type B, Type C) considering circuit design characteristics (thermal design, PCB patten spacing, element material) and it was experimented in the acceleration test conditions ($85^{\circ}C$, 85% R.H). Conclusion: We confirmed that failure mechanism of the ballast for LED Lamp had occurred differently in accordance with the circuit design characteristics.

• 산업경영시스템학회지
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• 제35권3호
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• pp.45-51
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• 2012

대기부품은 대기기간 중에 우발적 고장이 발생할 수 있으며(type I failure), 해당상황이 장기간 방치되는 것을 방지하기 위해 주기적인 검사를 하는 것이 일반적이다. 그러나 검사가 대기기간 중 발생한 고장을 확인할 수 있게 하는 반면, 검사를 시작할 때 대기하던 부품에 부하를 가하는 과정에서 고장을 유발할 가능성이 존재하며(type II failure), 검사시간동안 대기부품을 작동시킴으로써 열화에 의한 고장발생(type III failure)의 가능성을 증가시키는 효과도 존재한다. 이에 본 논문은 주기적 검사정책을 갖는 대기부품을 대상으로 세 종류의 고장 가능성을 확률적으로 고려하여 성능분석을 실시하였으며, 성능을 평가하는 척도로 극한가용성을 사용하였다. 특히 type III failure를 고려하는 것은 기존에 연구되지 않은 부분으로 본 논문의 기여점이라 할 수 있겠다. 또한 수치해석을 통해 가용성의 관점에서 전술한 세 가지 유형의 고장특성과 검사주기와의 관계를 파악할 수 있도록 하였으며, 그 결과를 통해 높은 수준의 신뢰성 확보가 목적인 대기시스템의 효율적인 운영을 위한 의사결정시 도움이 될 수 있도록 하였다.

• 대한산업공학회지
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• 제14권2호
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• pp.81-90
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• 1988

This paper is concerned with warranty cost models for a product with two types of failure ; type 1 failures corrected by minimal repair and type 2 failures removed only by replacement. Two warranty policies involving an initial free service period followed by a pro-rata period are considered ; the difference is whether the warranty is renewed or not when type 2 failure occures during its free service period. Expected warranty costs under the two policies are obtained, and their behaviors are examined for the case where type 1 and 2 failure distributions are Weibull and exponential, respectively.

• Communications for Statistical Applications and Methods
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• 제23권6호
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• pp.467-478
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• 2016

The accelerated failure time model or accelerated life model relates the logarithm of the failure time linearly to the covariates. The parameters in the model provides a direct interpretation. In this paper, we review some newly developed practically useful estimation and inference methods for the model in the analysis of right censored data.

• Steel and Composite Structures
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• 제19권6호
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• pp.1561-1580
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• 2015

No significant improvement has been observed on the seismic performance of the ordinary steel reinforced concrete (SRC) columns compared with the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type section steel were put forward on this background: a cross-shaped steel whose flanges are in contact with concrete cover by extending the geometry of webs, and a rotated cross-shaped steel whose webs coincide with diagonal line of the column's section. The advantages of new-type SRC columns have been proved theoretically and experimentally, while construction measures and seismic behavior remain unclear when the new-type columns are joined onto SRC beams. Seismic behavior of SRC joints with new-type section steel were experimentally investigated by testing 5 specimens subjected to low reversed cyclic loading, mainly including the failure patterns, hysteretic loops, skeleton curves, energy dissipation capacity, strength and stiffness degradation and ductility. Effects of steel shape, load angel and construction measures on seismic behavior of joints were also analyzed. The test results indicate that the new-type joints display shear failure pattern under seismic loading, and steel and concrete of core region could bear larger load and tend to be stable although the specimens are close to failure. The hysteretic curves of new-type joints are plumper whose equivalent viscous damping coefficients and ductility factors are over 0.38 and 3.2 respectively, and this illustrates the energy dissipation capacity and deformation ability of new-type SRC joints are better than that of ordinary ones with shear failure. Bearing capacity and ductility of new-type joints are superior when the diagonal cross-shaped steel is contained and beams are orthogonal to columns, and the two construction measures proposed have little effect on the seismic behavior of joints.

• 한국재료학회지
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• 제14권5호
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• pp.322-327
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• 2004

Copper-based leadframe sheets were oxidized in two kinds of hot alkaline solutions to form brown-oxide or black-oxide layer on the surface. The oxide coated leadframe sheets were molded with epoxy molding compound (EMC). After post mold curing, the oxide-coated EMC-leadframe joints were machined to form sandwiched Brazil-nut (SBN) specimens. The SBN specimens were used to measure the fracture toughness of the EMC/leadframe interfaces under mixed-mode (mode I + mode II) loading conditions. Fracture surfaces were analyzed by various equipment to investigate failure path. The results revealed that the failure paths were strongly dependent on the oxide type. In case of brown oxide, hackle-type failure was observed and failure path lay near the EMC/CuO interface with a little inclining to CuO at all case. On the other hand, in case of black oxide, quite different failure path was observed with respect to the distance from the tip of pre-crack and phase angle. Different failures occurred with oxide type is presumed to be due to the difference in microstructure of the oxides.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.813-822
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• 2008

The present work has been developed the interpretation processor including analysis of the failure stress in pyrotechnically releasable mechanical linking device, which has the release characteristic without fragmentation and pyro-shock, using SoildWorks, COSMOS Works and ANSYS programs. The aim of the invention is to propose a pyrotechnically releasable mechanical linking device for two mechanical elements that does not suffer from such drawbacks. The pyrotechnically releasable mechanical linking device according to the invention is simple, compact and inexpensive in structure. It is simple to implement and permit the use of only a reduced quantity of pyrotechnic composition, such composition possibly being devoid of any primary explosive at all. The present work is only focused on the design of structure and the material characteristics. To analyze the fracture morphology resulted from tensile test in the different ball type bolts, the present work has been performed to estimate the failure stress of material and to make the same result from tensile test. The failure stress of SUS 630 in ductile material is approximately 1050 Mpa. The failure stress of SUS 420 in brittle material is about 1790 Mpa. Among the models used the ductile material, the model 6 is suitable a design of structure compared to that of other models. The use of this interpretation processor developed the present work could be extensively helped to estimate the failure stress of material having a complex geometry such as the ball type bolt

• 비파괴검사학회지
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• 제27권6호
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• pp.520-530
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• 2007

Combination of the parametric and the wavelet analyses of acoustic emission (AE) signals was applied to identify the failure modes in carbon fiber reinforced plastic (CFRP) composite laminates during tensile testing. AE signals detected by surface mounted lead-zirconate-titanate (PZT) and polyvinylidene fluoride (PVDF) sensors were analyzed by parametric analysis based on the time of occurrence which classifies AE signals corresponding to failure modes. The frequency band level-energy analysis can distinguish the dominant frequency band for each failure mode. It was observed that the same type of failure mechanism produced signals with different characteristics depending on the stacking sequences and the type of sensors. This indicates that the proposed method can identify the failure modes of the signals if the stacking sequences and the sensors used are known.

• Journal of the Korean Data and Information Science Society
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• 제10권1호
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• pp.155-162
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• 1999

This paper is concerned with the empirical Bayes estimation of one of the two shape parameters(${\theta}$) in the Burr(${\beta},\;{\theta}$) type XII failure model based on type-II censored data. We obtain the bootstrap empirical Bayes confidence intervals of ${\theta}$ by the parametric bootstrap introduced by Laird and Louis(1987). The comparisons among the bootstrap and the naive empirical Bayes confidence intervals through Monte Carlo study are also presented.

• 콘크리트학회논문집
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• 제16권1호
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• pp.10-17
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• 2004

활하중 4903Pa를 적용하여 최소깊이로 최적 설계한, 실물크기 U형 보에 대하여 전단경간과 내민보 길이를 다르게 하여 4번의 전단실험을 수행하였다. 토핑 콘크리트를 타설한 경간 10.5m 실물크기 U형 합성보는 보의 폭/깊이 비가 2이상이다. 이프리캐스트 프리스트레스트 보의 단부 전단거동을 평가하는 과정에서 다음과 같은 결론을 얻을 수 있었다. 1) 이 합성 U형 보는 최종파괴에 이를 때까지 일체 거동하였으며, 강도설계 규준에 합당한 휨과 전단거동을 보여주었다. 2) 본 연구결과의 범위 안에서, 본 연구에서 고려한 보깊이가 얕은 U형 보의 전체정착길이는 집중하중 위치에 대한 ACI 정착길이 요구식이 정착부착파괴의 가부를 결정하는 기준이 되었다 3) 단부쪽에 발생한 전단균열은 모두 정착파괴로 연결되는 것이 아니며, 선행된 슬립이 존재할 때 정착부착파괴로 유도될 수 있다. 4) 보 중앙축 부근의 일반휨철근은 보의 연성파괴를 유도하는 역할을 위하여 효과적으로 활용될 수 있다.