• Title/Summary/Keyword: Degradation test

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Planning of Accelerated Degradation Tests: In the Case Where the Performance Degradation Characteristic Follows the Lognormal Distribution (성능특성치의 열화가 대수정규분포를 따를 때의 가속열화시험 모형 개발)

  • Lim, Heonsang;Sung, Si-Il
    • Journal of Applied Reliability
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    • v.18 no.1
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    • pp.80-86
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    • 2018
  • Purpose: This article provides a mathematical model for the accelerated degradation test when the performance degradation characteristic follows the lognormal distribution. Method: For developing test plans, the total number of test units and the test time are determined based on the minimization of the asymptotic variance of the q-th quantile of the lifetime distribution at the use condition. Results: The mathematical model for the accelerated degradation test is provided. Conclusion: Accelerated degradation test method is widely used to evaluate the product lifetime within a resonable amount of cost and time. In this article. a mathematical model for the accelerated degradation test method is newly developed for this purposes.

Degradation Mechanism of ZnO Ceramic Varistors with the Time on the DC Stress Test (DC 스트레스 시간에 따른 ZnO 세라믹 바리스터의 열화기구)

  • 소순진;김영진;소병문;박춘배
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.857-860
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    • 2000
  • The objective of this paper is to demonstrate degradation phenomena through DC degradation tests and predicts degradation phenomena as a function of time from the tests. The ZnO varistor used in this investigation were fabricated by standard ceramic techniques. Especial, these were sintered in nitrogen atmosphere, at 2 h, for $1300^{\circ}C$. The conditions of DC degradation test were 115$\pm$$2^{\circ}C$for 0, 2, 4, and 8 h, respectively. To demonstrate the degradation phenomena of ZnO varistors, Voltagecurrent analyses were performed before and after the degradation test, and frequency analyses were used with the time of the degradation tests. It was found that the degradation occurred in not grain but grain boundary and the degradation behavior of varistors was unsymmetrically degraded with the direction of tests.

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Analysis of Luminance Degradation characteristics of OLED using the Hotplate (핫플레이트를 이용한 OLED의 휘도열화특성 분석)

  • Kim, Yun-Cheol;Lee, Duek-Jung;Jang, Joong-Soon
    • Journal of Applied Reliability
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    • v.16 no.4
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    • pp.356-363
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    • 2016
  • Purpose: The purpose of this study is to propose efficiency of equipment testing the luminance degradation of OLED. Methods: The degradation model of Exponential model and Stretched exponential model is analyzed by goodness of fit test using calculated R-square. The degradation model having the higher R-square is finally selected. Scale parameter and Shape parameter using the selected degradation model is estimated. The activation energy and current density n using peck model among the accelerated model is estimated. the estimated parameters are analyzed by t-test. Results: The results of t-test show that the estimated parameters on chamber and hotplate are equal statistically. we can know the similarity of the luminance degradation rate and degradation pattern on chamber and hotplate. Conclusion: The result of the degradation test on chamber and hotplate is similar. when the accelerated degradation test on the panel of the OLED TV is performed, hotplate is requiring less samples, time and cost than chamber. so the accelerated degradation test on the panel of the OLED TV using the hoplate is efficient of time and cost.

Towards improved models of shear strength degradation in reinforced concrete members

  • Aschheim, Mark
    • Structural Engineering and Mechanics
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    • v.9 no.6
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    • pp.601-613
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    • 2000
  • Existing models for the shear strength degradation of reinforced concrete members present varied conceptual approaches to interpreting test data. The relative superiority of one approach over the others is difficult to determine, particularly given the sparseness of ideal test data. Nevertheless, existing models are compared using a suite of test data that were used for the development of one such model, and significant differences emerge. Rather than relying purely on column test data, the body of knowledge concerning degradation of concrete as a material is considered. Confined concrete relations are examined to infer details of the degradation process, and to establish a framework for developing phenomenologically-based models for shear strength degradation in reinforced concrete members. The possibility of linking column shear strength degradation with material degradation phenomena is explored with a simple model. The model is applied to the results of 7 column tests, and it is found that such a link is sustainable. It is expected that models founded on material degradation phenomena will be more reliable and more broadly applicable than the current generation of empirical shear strength degradation models.

Strength Evaluation and Life Prediction of the Multistage Degraded Materials (다단계 모의 열화재의 재료강도 평가와 수명예측)

  • 권재도;진영준;장순식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2271-2279
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    • 1993
  • In the case of life prediction on the structures and machines after long service, it is natural to consider a degradation problems. Most of degradation data form practical structures are isolated data obtained at the time of periodical inspection or repair. From such data, it may be difficult to obtain the degradation curve available and necessary for life prediction. In this paper, for the purpose of obtaining a degradation curves, developed the simulate degradation method and fatigue test and Charpy impact test were conducted on the degraded, simulate degraded and recovered materials. Fatigue life prediction were conducted by using the relationship between fracture transition temperature (DBTT : vTrs) obtained from the Charpy impact test through the degradation process and fatigue crack growth constants of m and C obtained from the fatigue test.

Application of Accelerated Degradation Testing for VFD (Vacuum Fluorescent Display) (VFD(Vacuum Fluorescent Display) 가속열화시험 응용사례)

  • Bae, Suk-Joo
    • Journal of Applied Reliability
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    • v.5 no.4
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    • pp.413-425
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    • 2005
  • As an alternative to traditional life testing, degradation tests can be effective in assessing product reliability when measurements of degradation leading to failure can be observed. This article presents an accelerated degradation testing for vacuum fluorescent displays (VFDs). The accelerated degradation model is based on Arrhenius-lifetime relationship for cathode temperatures. We compare the results between accelerated degradation test and test at normal use condition. Accelerated degradation test for display devices is observed as an efficient method to warrantee product reliability to customers, as well as a tool to save time and costs.

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An Accelerated Degradation Test of a Electronics Appliance Compressor (전자제품용 컴프레서의 가속열화시험에 관한 연구)

  • Lee, Hoo-Jin;Yun, Won-Young
    • Journal of Applied Reliability
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    • v.10 no.1
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    • pp.25-38
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    • 2010
  • In this paper, an accelerated degradation test procedure for an electronic appliance compressor is proposed. We investigate the amount of wear of the compressor and consider several factors as accelerating factors. Finally we select the operating pressure as a main accelerating factor. The test condition of accelerated degradation test is determined. The modified accelerating test reduces the test time in design phase by using the suggested accelerating factor.

Design of Accelerated Degradation Test with Tightened Critical Values under Random Coefficient Degradation Rate Model (확률계수 열화율 모형하에서 판정가속을 도입한 가속열화시험의 설계)

  • Cho, You-hee;Seo, Sun-keun
    • Journal of Korean Institute of Industrial Engineers
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    • v.34 no.1
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    • pp.23-31
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    • 2008
  • This paper presents accelerated degradation test plans considering adoption of tightened critical values. Under arandom coefficient degradation rate and log-linear acceleration models, the asymptotic variance of an estimatorfor a lifetime quantile at the use condition as the optimization criterion is derived where the degradation ratefollows a lognormal and Reciprocal Weibull distributions, respectively and then the low stress level andproportions ofunits allocated to each stress level are determined. We also show that the developed test plans canbe applied to the multiplicative model with measurement error.

A Study on Advanced Small Punch Test for Evaluation of Material Degradation in Weldment Microstructures (용접부 미세조직의 재질열화 평가를 위한 Advanced Small Punch 시험에 관한 연구)

  • 이동환;이송인;박종진;유효선
    • Journal of Welding and Joining
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    • v.21 no.1
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    • pp.99-106
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    • 2003
  • This research was aimed to evaluate the material degradation with various microstructures of X20CrMoV121 steel weldment by Advanced Small Punch(ASP) test. Due to the regional limitation on constitutive structures, the minimized loading ball(${\varphi}1.5mm$) and bore diameter of lower die(${\varphi}3mm$) were designed for the ASP test. The micro-hardness test was also performed to assess the mechanical properties with artificial aging heat treatment. Material degradation was estimated by ductile-brittle transition temperature(DBTT). The results obtained from the ASP test were compared with those from conventional small punch(CSP) test and CVN impact test for several weldment microstructures. It was found that the ASP test clearly showed the microstructural dependance on the material degradation in the weldment.

Service Life Prediction of Components or Materials Based on Accelerated Degradation Tests (가속열화시험에 의한 부품·소재 사용수명 예측에 관한 연구)

  • Kwon, Young Il
    • Journal of Applied Reliability
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    • v.17 no.2
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    • pp.103-111
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    • 2017
  • Purpose: Accelerated degradation tests can speed time to market and reduce the test time and costs associated with long term reliability tests to verify the required service life of a product or material. This paper proposes a service life prediction method for components or materials using an accelerated degradation tests based on the relationships between temperature and the rate of failure-causing chemical reaction. Methods: The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed and least square estimation is used to estimate model parameters from the degradation model. Results: Methods of obtaining acceleration factors and predicting service life using the degradation model are presented and a numerical example is provided. Conclusion: Service life prediction of a component or material is possible at an early stage of the degradation test by using the proposed method.