• Title/Summary/Keyword: 피로 신뢰성평가

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Statistical Analysis for Fatigue Life Evaluation of Vehicle Muffler (자동차용 머플러의 피로수명평가를 위한 통계적 분석)

  • Choi, Ji-Hun;Lee, Yong-Jun;Yoon, Jin-Ho;Kang, Sung-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.3
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    • pp.365-372
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    • 2013
  • In this study, a statistical method for evaluating the fatigue life of a vehicle muffler was used to obtain reliable fatigue data using a limited number of specimens. Cyclic bending tests were conducted using specimens manufactured to be exactly the same as the mufflers installed in cars that are currently in use. To estimate the fatigue life by comparing the data obtained during the fatigue tests, the most suitable probability density function for the normal, lognormal, and Weibull distributions was selected. A goodness-of-fit test was performed on the probability distributions, and then a Weibull distribution using the least square method was selected. By using the selected Weibull distribution, the probability-moment-life curves (P-M-N curve) reflecting the fatigue characteristics were suggested as the data for the reliable design of a muffler.

Development of Integrated Design System for Mechanical Rubber Components (고무류 기계부품 통합설계시스템 개발)

  • Woo, Chang-Su;Kim, Wan-Doo;Kim, Young-Gil;Shin, Wae-Gi;Lee, Seong-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.1045-1050
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    • 2010
  • Fatigue analysis and lifetime evaluation are very important in design procedure for assuring the safety and reliability of rubber components for mechanical systems. Till recently, the technology for the design, analysis, and evaluation of rubber products was required to manufacture rubber products with high quality, fidelity, and reliability. However, in the rubber-manufacturing companies in Korea, the processes of compound mixing, manufacturing of rubber products, and improvement of rubber properties are based on the trial-and-error method and experience. The objectives of this study are to establish methods for testing rubber materials, to develop a database of the properties of rubber materials, to evaluate the performance of rubber components, and to develop a system for predicting fatigue life. A method to predict fatigue-life of rubber components was proposed; in this method, the finite-element analysis and fatigue damage parameter as determined from a fatigue test are incorporated.

Subjective Measures of Operator Status in Surface Transportation: h Critical Review and Recommendations for Application (지상 교통에 있어서 운전자 상태의 주관적 척도: 비판적 고찰 및 응용을 위한 제언)

  • Heidi D. Howarth;Sohn, Young-Woo
    • Science of Emotion and Sensibility
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    • v.5 no.4
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    • pp.11-32
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    • 2002
  • This article evaluates the existing subjective measures that have been utilized in surface transportation to assess various aspects of operator status such as fatigue, sleepiness, arousal, mood, etc. Specifically, the representative six subjective instruments - Epworth Sleepiness Scale, Karolinska Sleepiness Scale, Pearson and Byars Fatigue Checklist, Stanford Sleepiness Scale, Stress-Arousal Checklist, and NPRU Mood Scale - are compared and contrasted in terms of reliability, . validity, sensitivity, and appropriateness for application. Recommendations for application of the subjective measures in surface transportation are discussed.

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Corrosion Fatigue Reliability-Based Life Cycle Cost Analysis of High-Speed Railway Steel Bridges (고속철도 강교량의 부식 피로신뢰성 기반 생애주기비용 분석)

  • Cho, Hyo-Nam;Jeon, Hong-Min;Sun, Jong-Wan;Youn, Man-Keun
    • Journal of the Korean Society for Railway
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    • v.11 no.1
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    • pp.107-113
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    • 2008
  • As it recently appears that LCC (Life Cycle Cost) analysis may be considered as an essential method for economic evaluation of infrastructures. Many researches have been made to assess LCC of each facility based on reasonable methods. However, expected maintenance repair cost must be reasonably estimated to enhance the reliability of LCC analysis through systematic and rational methods. This study is intended to propose a rational approach to reliability-based LCC analysis of high-speed railway steel bridges considering lifetime corrosion and fatigue damage. However in Korea, since high speed railway steel bridges are only recently constructed, no direct statistical data are available for the account of the maintenance cost and thus their maintenance characteristics are not clear yet. In this paper, for the assessment of expected maintenance/repair cost, the fatigue system reliability analysis incorporating the corrosion effect is proposed by considering the corrosion and fatigue damage using measured data of high speed railway steel bridges. A model proposed by Rahgozar, of at for fatigue notch factor considering the corrosion effect is used in order to incorporate the corrosion effect into the fatigue strength reduction and S-N curve. Finally, the effectiveness of LCC model proposed for high-speed railway steel bridges is demonstrated by a numerical example.

통합형 점소성 구성방정식을 적용한 유한요소해석에 관한 연구

  • Kim, Jong-Beom;Lee, Hyeong-Yeon;Yoo, Bong;Kwak, Dae-Young;Lim, Yong-Taek
    • Proceedings of the Korean Nuclear Society Conference
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    • 1995.05a
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    • pp.1014-1020
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    • 1995
  • 고온구조물은 고온에서의 운전상태에 따라 복잡한 하중이력을 경험하게 됨으로써 상온에서 발생하는 손상 기구와는 달리 온도 의존성을 가질 뿐만 아니라, 상온에서 볼 수 없는 크립-피로의 상호작용에 의한 손상현상이 나타나게 된다. 따라서 고온 구조물의 건전성 평가를 위한 비탄성 해석을 신뢰성 있게 수행하기 위해서는 구조물의 비선형 거동을 비교적 정확히 예측할 수 있는 통합 구성방정식의 개발 및 적용과 온도에 따른 재료의 물성치 확보가 필수적이다. 본 연구에서는 통합 점소성 모델인 수정된 Chaboche 모델에 대해서 내연적 시간 적분법을 적용하여 ABAQUS의 UMAT으로 구현하였고, 개발된 프로그램을 이용하여 INCONEL 718을 사용한 단순 인장해석, 반복 소성 특성해석 및 크립 해석을 수행하여 프로그램의 신뢰성을 평가하였다. 또한 원공이 있는 평판에 대한 예제해석을 수행함으로써 개발된 프로그램이 고온구조물의 건전성 평가를 위한 비탄성 해석에 적절하게 적용될 수 있음을 확인하였다.

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Reliability Assessment of Lead-contained and Lead-free BGA Solder Joints under Cyclic Bending Loads (굽힘 하중하에서 유연 및 무연 솔더 조인트의 신뢰성 평가)

  • Kim Il-Ho;Lee Soon-Bok
    • Journal of the Microelectronics and Packaging Society
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    • v.13 no.1 s.38
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    • pp.63-72
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    • 2006
  • Mobile products, such as cellular phones, PDA and notebook, are subjected to many different mechanical loads, which include bending, twisting, impact shock and vibration. In this study, a cyclic bending test of the BGA package was performed to evaluate the fatigue life. Special bending tester, which was suitable for electronic package, was developed using an electromagnetic actuator. A nonlinear finite element model was used to simulate the mechanical bending deformation of solder joint in BGA packages. The fatigue life of lead-free (95.5Sn4.0Ag0.5Cu) solder joints was compared with that of lead-contained (63Sn37Pb). When the applied load to the specimen is small, the lead-free solder has longer fatigue life than lead-contained solder. The fatigue crack is initialized at the exterior solder joints and is propagated into the inner solder joints.

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A Study on the Flexural Fatigue Performance Evaluation of Copolymer Aramid Fiber (공중합 아라미드의 굴곡피로성능 평가에 관한 연구)

  • Hong Jin Yoon;Dong Ki Oh;Chang Ju Kim;Jong Dae Lee
    • Korean Chemical Engineering Research
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    • v.62 no.4
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    • pp.355-363
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    • 2024
  • Although copolymer aramid is a fiber with excellent flexural performance, there is no test method to evaluate flexural fatigue performance. Various studies are currently being conducted in korea to develop copolymer aramid, and in order to develop the reliability of aramid fibers to a global level, it is necessary to develop a test method to evaluate the flexural fatigue performance of aramid fibers. In this study, we developed an test equipment and test method that can evaluate the flexural fatigue performance of copolymer aramid and analyzed the flexural fatigue performance of aramid fiber. Flexing rollers are made of ceramic materials and rotating shapes to minimize friction. The diameter of the roller was set to 10 mm by calculating the minimum allowable curvature. The B10 life was calculated through a flexural fatigue test, and the para-aramid was 125,770 cycles, the copolymer aramid was 598,150 cycles, and the aramid nano fiber(ANF) coated copolymer aramid was 589,073 cycles. Through the S-N diagram, the fatigue life relationship according to the load change was confirmed. copolymer aramid fibers exhibit better flexural fatigue performance than para-aramid fibers at high loads. The ANF coated copolymer aramid also exhibits excellent flexural fatigue performance.

An Estimating Reliability of Machine Elements Subjected to Fluctuating Load Considering Static and Dynamic Allowable Safety Factors (변동하중시 정ㆍ동적 허용안전계수를 고려한 기계부품의 신뢰성 평가)

  • 양성모;강희용;김강희
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.4
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    • pp.51-57
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    • 1998
  • It is common to assume identical allowable safety factors in static strength defined by mean stress and in fatigue, defined by stress amplitude. Under the load with asymmetrical cycles the safety factor is not the same. In this paper, with the consideration of unequal allowable safety (actors a general method for estimating fatigue reliability of a machine element under a combined state of stress is derived based on the theory proposed by Prof. Kececioglu and a normal distribution. The calculation of fatigue reliability fur limited life is discussed with example.

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A Study on the Fatigue Reliability of Structures by Markov Chain Model (Markov Chain Model을 이용한 구조물의 피로 신뢰성 해석에 관한 연구)

  • Y.S. Yang;J.H. Yoon
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.228-240
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    • 1991
  • Many experimental data of fatigue crack propagation show that the fatigue crack propagation process is stochastic. Therefore, the study on the crack propagation must be based on the probabilistic approach. In the present paper, fatigue crack propagation process is assumed to be a discrete Markov process and the method is developed, which can evaluate the reliability of the structural component by using Markov chain model(Unit step B-model) suggested by Bogdanoff. In this method, leak failure, plastic collapse and brittle fracture of the critical component are taken as failure modes, and the effects of initial crack distribution, periodic and non-periodic inspection on the probability of failure are considered. In this method, an equivalent load value for random loading such as wave load is used to facilitate the analysis. Finally some calculations are carried out in order to show the usefulness and the applicability of this method. And then some remarks on this method are mentioned.

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Accelerated Life Evaluation of Propeller Shaft for Forklift Truck (지게차용 추진축의 가속 수명 평가)

  • Kim, Do-Sik;Sung, Baek-Ju
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.11
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    • pp.1221-1229
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    • 2014
  • This paper proposes an approach for predicting the fatigue life of a propeller shaft of a forklift truck by an accelerated life test method. The accelerated life test method adopted in this study is the calibrated accelerated life test, which is highly effective in the prediction of the lifetime and enables significant reduction of the test time as well as a quantification of reliability in the case of small sample sizes. First, the fatigue test was performed under two high stress levels, and then, it was performed by setting low stress levels in consideration of the available test time and extrapolation. Major reliability parameters such as the lifetime, accelerated power index, and shape parameter were obtained experimentally, and the experimentally predicted lifetime of the propeller shaft was verified through comparison with results of an analysis of load spectrum data under actual operating conditions.