• 제목, 요약, 키워드: failure mechanism

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가변 고장메카니즘을 가진 가속수명시험 데이타 분석방법 (An Analysis Method of Accelerated Life Test Data with a Change of Failure Mechanism)

  • 원영철;공명복
    • 대한산업공학회지
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    • v.20 no.1
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    • pp.39-51
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    • 1994
  • Almost all accelerated life tests assume that no basic failure mechanism changes within the test stresses. But accelerated life test, considering failure mechanism changes, is needed since failure mechanism changes when accelerating beyond the used stress. This paper studies the analysis when the failure mechanism changes within the test stresses. The piecewise linear regression, which the join point of two lines is estimated, is applied In particular, two accelerated life tests, with and without a change in failure mechanism are examined.

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암반 사면의 복합 파괴 메커니즘 규명 (Complex failure mechanism of rock slopes)

  • 윤운상;정의진;박성욱;최재원
    • 한국지반공학회:학술대회논문집
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    • pp.268-273
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    • 2006
  • Slope failures can be occurred by complex mechanism. In this cases, failures shows characteristics of complex failure mechanism during progressive mass movements. A case is a merged large slide with two sliding events triggered by slip on fault plane. Another case shows extension of failure area by sliding or subsidence at backyards of toppling areas. Generally, areas of progressive failures have wider than them of simple events.

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An improved collapse analysis mechanism for the face stability of shield tunnel in layered soils

  • Chen, Guang-hui;Zou, Jin-feng;Qian, Ze-hang
    • Geomechanics and Engineering
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    • v.17 no.1
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    • pp.97-107
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    • 2019
  • Based on the results of Han et al. (2016), in the failure zone ahead of the tunnel face it can be obviously identified that a shear failure band occurs in the lower part and a pressure arch happens at the upper part, which was often neglected in analyzing the face stability of shield tunnel. In order to better describe the collapse failure feature of the tunnel face, a new improved failure mechanism is proposed to evaluate the face stability of shield tunnel excavated in layered soils in the framework of limit analysis by using spatial discretization technique and linear interpolation method in this study. The developed failure mechanism is composed of two parts: i) the rotational failure mechanism denoting the shear failure band and ii) a uniformly distributed force denoting the pressure arch effect. Followed by the comparison between the results of critical face pressures provided by the developed model and those by the existing works, which indicates that the new developed failure mechanism provides comparatively reasonable results.

가전제품용 경첩의 신뢰성 추정 (Reliability Estimation of Door Hinge for Home Appliances)

  • 문지섭;김진우;이재국;이희진;신재철;김명수
    • 한국신뢰성학회:학술대회논문집
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    • pp.303-311
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    • 2004
  • This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, B$_{10}$ life and its lower bound with 90% confidence at worst case use condition are estimated by analyzing the accelerated life test data.a.

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가전제품용 경첩의 신뢰성 추정 (Reliability Estimation of Door Hinge for Rome Appliances)

  • 김진우;신재철;김명수;문지섭
    • 대한기계학회논문집A
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    • v.29 no.5
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    • pp.689-697
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    • 2005
  • This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, $B_{10}$ life and its lower bound with $90\%$ confidence at worst case use condition are estimated by analyzing the accelerated life test data.

The investigation of rock cutting simulation based on discrete element method

  • Zhu, Xiaohua;Liu, Weiji;Lv, Yanxin
    • Geomechanics and Engineering
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    • v.13 no.6
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    • pp.977-995
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    • 2017
  • It is well accepted that rock failure mechanism influence the cutting efficiency and determination of optimum cutting parameters. In this paper, an attempt was made to research the factors that affect the failure mechanism based on discrete element method (DEM). The influences of cutting depth, hydrostatic pressure, cutting velocity, back rake angle and joint set on failure mechanism in rock-cutting are researched by PFC2D. The results show that: the ductile failure occurs at shallow cutting depths, the brittle failure occurs as the depth of cut increases beyond a threshold value. The mean cutting forces have a linear related to the cutting depth if the cutting action is dominated by the ductile mode, however, the mean cutting forces are deviate from the linear relationship while the cutting action is dominated by the brittle mode. The failure mechanism changes from brittle mode with larger chips under atmospheric conditions, to ductile mode with crushed chips under hydrostatic conditions. As the cutting velocity increases, a grow number of micro-cracks are initiated around the cutter and the volume of the chipped fragmentation is decreasing correspondingly. The crack initiates and propagates parallel to the free surface with a smaller rake angle, but with the rake angle increases, the direction of crack initiation and propagation is changed to towards the intact rock. The existence of joint set have significant influence on crack initiation and propagation, it makes the crack prone to propagate along the joint.

Resiliency Design of a Loosely-Coupled Database System

  • Park, Jae-Hwa;Kim, Sung-Eon
    • 한국정보시스템학회지:정보시스템연구
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    • v.4
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    • pp.85-104
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    • 1995
  • In a loosely-coupled distributed database server system, a server failure and/or a communication failure can be masked by a resiliency mechanism. Recognizing that a distributed transaction executes at several servers during its lifetime, we propose a resiliency mechanism which allows continuous transaction processing in distributed database server systems in the presence of a server failure. The resiliency mechanism for transaction processing is achieved by keeping redundant information using a primary/backup approach. The purpose of this paper is to analyze the performance improvement opportunities with the resiliency mechanism and to present the design of the proposed system.

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Bendable 임베디드 전자모듈의 손상 메커니즘 (Failure Mechanism of Bendable Embedded Electronic Module Under Various Environment Conditions)

  • 조윤성;김아영;홍원식
    • Journal of Welding and Joining
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    • v.31 no.5
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    • pp.59-63
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    • 2013
  • A bendable electronic module has been developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In flexible embedded electronic module, a thin silicon chip was embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. To confirm reliability and durability of prototype bendable module, the following tests were conducted: Moisture sensitivity level, thermal shock test, high temperature & high humidity storage test, and pressure cooker tester. Those experiments to induce failure of the module due to temperature variations and moisture are the experiment to verify the reliability. Failure criterion was 20% increase in bump resistance from the initial value. The mechanism of the increase of the bump resistance was analyzed by using non-destructive X-ray analysis and scanning acoustic microscopy. During the pressure cooker test (PCT), delamination occurred at the various interfaces of the bendable embedded modules. To investigate the failure mechanism, moisture diffusion analysis was conducted to the pressure cooker's test. The hygroscopic characteristics of the encapsulating polymeric materials were experimentally determined. Analysis results have shown moisture saturation process of flexible module under high temperature/high humidity and high atmosphere conditions. Based on these results, stress factor and failure mechanism/mode of bendable embedded electronic module were obtained.

고 출력 백색 변환용 LED(3W용)의 고장메커니즘 비교 (A Comparison of the Failure Mechanism for High Power Converted White LEDs(3W))

  • 윤양기;장중순
    • 한국신뢰성학회지:신뢰성응용연구
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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.

자동차용 깊은홈 볼베어링의 조기파손 : 1보 - 파손기구의 규명 (Premature Failure of Deep Grooved Ball Bearing for Automobiles : Part 1 - A Failure Mechanism)

  • 현준수;박태조
    • 한국윤활학회:학술대회논문집
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    • pp.388-394
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    • 2003
  • This paper deals with a premature failure mechanism of deep grooved ball bearing for automobiles. A close examination of used bearings revealed that the premature failure could be arose by dents on the ball. Universal testing machine with specially designed tools is used to simulate the practical dents on the ball and test bearings are assembled with dented balls and new hearing components. The endurance test results showed that the dents on the balls were printed on the races and these phenomena come to premature failure.

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