• Title/Summary/Keyword: residual life

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The Asymptotic Properties of Mean Residual Life Function on Left Truncated and Right Censoring Model

  • Moon, Kyoung-Ae;Shin, Im-Hee
    • Journal of the Korean Data and Information Science Society
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    • v.8 no.1
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    • pp.99-109
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    • 1997
  • The estimation procedure of mean residual life function has been placed an important role in the study of survival analysis. In this paper, the product limit estimator on left truncated and right censoring model is proposed with asymptotic properties. Also, the small sample properties are investigated through the Monte Carlo study and the proposed product limit type estimator is compared with ordinary Kaplan-Meier type estimator.

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Mean Residual Life Times (평균잔여수명함수(平均殘餘壽命函數)의 추정(推定))

  • Lee, Sang-Bock;Park, Byung-Gu
    • Journal of the Korean Data and Information Science Society
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    • v.2
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    • pp.11-21
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    • 1991
  • A different approach to the evaluation of mean residual life function under the random censorship model is presented. For small sample sizes, the performances between the proposed estimator and other estimators for men residual life function are compared in terms of bias and mean square error via a Monte Carlo study.

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Fatigue Life Prediction of Weldment with Damage Mechanics (손상역학을 이용한 용접부의 피로수명예측)

  • Chung, Heung-Jin;Yoo, Byoung-Chan
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.60-64
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    • 2008
  • According to previous research, welding-induced stress in steel structures can significantly affect the fatigue behaviour; it produces initial damage of weldiug part of structure locally and residual stresses reduce the fatigue strength after welding precess. In this study, through continuum damage mechanics, we can estimate the weldiug damage using the stress and strain history during welding process and the effect of welding residual stress for assessment of fatigue life. The variation of welding-induced stresses and strains need be traced precisely in advance for a reliable weldiug damage assessment. In this study, a damage and fatigue analysis techniques for steel structures with welding-induced residual stress are presented. First, We calculate the history of temperature according with welding process. And residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis. Secondly, welding damage and fatigue life are estimated with kinetic damage law.

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Fatigue Life Evaluation Model for Welded feints Based on Nominal Stress and Residual Stress Relaxation (잔류응력 완화를 고려한 공칭응력 기반 용접재의 피로수명 평가 모델)

  • 구병춘;양승용;정흥채;최성규
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.249-251
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    • 2004
  • According to our fatigue tests carried out at 20 ㎐, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short hie range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

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A Proposal of parameter Determination Method in the Residual Strength Degradation Model for the Prediction of Fatigue Life(II) (피로수명예측을 위한 잔류강도 저하모델의 파라미터 결정법 제안(II))

  • Kim, Sang-Tae;Jang, Seong-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.9
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    • pp.1452-1460
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    • 2001
  • A new method of parameter determination in the fatigue residual strength degradation model is proposed. The new method and minimization technique is compared experimentally to account for the effect of tension-compression fatigue loading of spheroidal graphite cast iron and graphite/epoxy laminate. It is shown that the correlation between the experimental results and the theoretical prediction on the fatigue life and residual strength distribution using the proposed method is very reasonable. Therefore, the proposed method is more adjustable in the determination of the parameter than minimization technique for the prediction of the fatigue characteristics.

BIVARIATE DYNAMIC CUMULATIVE RESIDUAL TSALLIS ENTROPY

  • SATI, MADAN MOHAN;SINGH, HARINDER
    • Journal of applied mathematics & informatics
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    • v.35 no.1_2
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    • pp.45-58
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    • 2017
  • Recently, Sati and Gupta (2015) proposed two measures of uncertainty based on non-extensive entropy, called the dynamic cumulative residual Tsallis entropy (DCRTE) and the empirical cumulative Tsallis entropy. In the present paper, we extend the definition of DCRTE into the bivariate setup and study its properties in the context of reliability theory. We also define a new class of life distributions based on bivariate DCRTE.

UNIFORM ASYMPTOTICS IN THE EMPIRICAL MEAN RESIDUAL LIFE PROCESS

  • Bae, Jong-Sic;Kim, Sung-Yeun
    • Journal of the Korean Mathematical Society
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    • v.43 no.2
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    • pp.225-239
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    • 2006
  • In [5], Csorgo and Zitikis exposed the strong $uniform-over-[0,\;{\infty}]$ consistency, and weak $uniform-over-[0,\;{\infty}]$ approximation of the empirical mean residual life process by employing weight functions. We carry on the uniform asymptotic behaviors of the empirical mean residual life process over the whole positive half line by representing the process as an integral form. We compare our results with those of Yang [15], Hall and Wellner [8], and Csorgo and Zitikis [5].

Numerical analysis of local exhaust effectiveness using reverse-flow calculation method (역유동계산법을 이용한 국소배기효율의 수치해석)

  • 한화택
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.6
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    • pp.658-665
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    • 1998
  • This paper investigates local exhaust effectiveness in a room with a supply and an exhaust slots on the ceiling. The mean age of air is an indicator of supply effectiveness, while the mean residual life time can be used as an indicator of exhaust effectiveness. The distribution of local mean residual life time in a space is calculated by four different numerical procedures. The reverse-flow calculation method has been proved to show quite accurate results while it can save considerable amount of computation time and efforts, compared to the method by its original definition. It is concluded that the diffusion term in the equation of mean residual life time can be neglected. The spatial and temporal diffusion characteristics of the contaminant are also discussed.

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Effect of Shot Peening on Fatigue Life of Heat Treated Spring Steel (열처리된 스프링강의 피로수명 개선을 위한 쇼트피닝 가공 효과)

  • Lee, Seung-Ho;Shim, Dong-Suk
    • Journal of the Korean Society for Heat Treatment
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    • v.17 no.6
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    • pp.336-341
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    • 2004
  • The effect of shot peening conditions on the fatigue properties of heat-treated spring steel has been investigated by using residual stress measurement and metallography. The mechanical properties of material did not change so much by shot peening. However, the fatigue strength and fatigue life increased about 20% to 40% by 1-step and 2-step shot peening process. The fatigue strength and life were closely related to the value and position of maximum compressive residual stress by shot peening process. In the case of warm shot peening, compressive residual stress of specimens shot peening processed at $200^{\circ}C$ was higher than those of specimens shot peening processed at room temperature, $100^{\circ}C$ and $300^{\circ}C$.

Finite Element Analysis of Re-Cold Expansion in Order to Improve the Fatigue Life of Fastener Hole that has been Cold Expanded Before (홀확장법을 적용한 체결홀의 피로수명 개선을 위한 재 홀확장 효과에 대한 유한요소 해석)

  • Jang, Jae-Soon;Yang, Won-Ho;Cho, Myoung-Rea
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.9 s.252
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    • pp.1110-1115
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    • 2006
  • Cold expansion of fastener holes has been successfully used for many years to impart beneficial compressive residual stresses. Beneficial compressive residual stress of fastener hole that has been cold expanded before is reduced by using of materials for a long time. As a result, fatigue life of material is reduced. So, compressive residual stresses of material have to regenerate by re-cold expansion method. In this paper, it was carried out a finite element analysis about variation of residual stress due to tensile stress and residual stress distribution that was regenerated by re-cold expansion method in the fastener hole. Here, a diversity tensile stress was used. Also, it was performed a finite element analysis according to cold expansion rate of re cold expansion in order to obtain a beneficial compressive residual stress.