• 항공우주시스템공학회지
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• 제14권6호
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• pp.58-67
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• 2020

In this study, finite element fatigue analysis combined with a fatigue correlation factor is proposed to predict the bending fatigue life of a gear in an electro-mechanical aircraft actuator. First, stress-life curves are obtained for the gear material via a round bar fatigue test. Subsequently, stochastic stress-life (P-S-N) curves are derived for 50% and 1% failure probabilities, separately. The curves are applied to the fatigue analysis model of a single gear tooth, and the effect of the fatigue correction factor is analyzed. The analytical P-S-N curves reflecting the fatigue correction factor matched the experimental data. This shows that the analytical fatigue life is reliable and that the analysis technique is effective.

• 한국세라믹학회지
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• 제30권3호
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• pp.229-235
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• 1993

Thermal history and thermal stress of alumina specimen, which occured from thermal shock process, were calculated by finite difference method. Stress intensity factor and crack growth in cyclic thermal fatigue were calculated from single thermal shock temperature history and thermal stress. Cyclic thermal life were estimated by bending strength after cyclic thermal shock under critical thermal shock temperature. Calculated stress intensity factor was compared with real experimental thermal fatigue life of specimen. Fatigue life until critical stress intensity factor and real experimental result were comparable.

• Journal of Welding and Joining
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• 제6권1호
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• pp.28-34
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• 1988

The fatigue test was carried out to evaluate the fatigue characteristics of the accelerated cooled (ACC) TMCP steel and its welded joint. From this study, it was confirmed that ACC TMCP steel has higher fatigue strength than conventional steels. After welding, however, the fatigue strength of ACC TMCP steel was deteriorated associated with HAZ softening when weld reinforcement was removed. On the other hand, with weld reinforcement, there is no effect of HAZ softening on the fatigue strength of welded joint because it is strongly dependant on the detail weld geometry i.e., stress concentration factor. Accordingly the fatigue strength of actual welded joint increases with decreasing the stress concentration factor of welded joint, regardless of HAZ softening.

• 한국안전학회지
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• 제15권3호
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• pp.1-6
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• 2000

In fatigue crack growth test, it is important not only to analyze characteristics of fatigue crack growth but also to determine the threshold stress intensity factor, ${\Delta}K_{th}$. which is the threshold value of fatigue crack growth. Linear regression analysis using fatigue test data near the threshold is suggested to determine the ${\Delta}K_{th}$ in the standard test method but the ${\Delta}K_{th}$ can be affected by a fitting method. And there are some limitations on the linear regression analysis in the case of small number of test data near the threshold. The objective of this study is to investigate differences of the ${\Delta}K_{th}$ due to regression analysis method and to evaluate the relative error range of the ${\Delta}K_{th}$ in same fatigue crack growth test data.

• 성인간호학회지
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• 제17권3호
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• pp.435-443
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• 2005

Purpose: This study investigated the degree of fatigue of hemodialysis patients, and finds the relationship between fatigue and self-efficacy, family support, and sleep factor. Also, this study was purposed to provide fundamental data to help set up a nursing plan and intervention for recovery and mitigation of hemodialysis patient's fatigue. Method: The subjects in this study were patients treated as hemodialysis patients in Kwangjoo City. Data, subjects are 143 patients. Fatigue was measured using Lee's scale(1991), Self-efficacy using Kim's scale(1995), and Family support using Kim's scale(1993). For the analysis of collected data, Cronbach alpha, descriptive statistics, t-test, ANOVA, Pearson's correlation coefficient, Stepwise multiple regression were used for statistical analysis by SPSSwin(version 11.0) program. Result: Fatigue degree of hemodialysis patients averaged 4.22. Among 143 hemodialysis patients, 70.63% patients answered that they had felt fatigue as noted in this study. The weariest time was after hemodialysis for 21.0% patients. There was significant difference according to the diagnosis period. The patients who were diagnosed over one year had felt more fatigue than ones who were diagnosed within one year. Fatigue was significantly associated with self-efficacy, family support, and sleep factor. Self-efficacy could explain 14.6% of fatigue. Conclusion: The fatigue degree relates with all, self-efficacy, family support, and sleep factor. Especially, it is affected by self-efficacy among them. Thus, the program should be developed to mitigate fatigue as the self-efficacy of hemodialysis is enhanced.

• 해양환경안전학회지
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• 제18권6호
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• pp.551-556
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• 2012

피로도는 인간의 업무수행능력에 유해한 영향을 미치는 것으로 알려져 있다. 또한 피로도는 해기사와 선박승무원의 효율성과 능률을 감소시킬 수 있다. 본 연구의 목적은 해기사들의 피로도 현황을 파악하기위한 것이다. 본 연구에서는 해기사의 피로도 요소와 관련된 근무, 수면 및 휴식시간이나 기간, 졸음, 유발요인, 피로도 증상 등에 대한 설문조사를 실시하였다. 설문조사는 25문항 이었으며, 1,033명의 해기사(항해사 607명, 기관사 426명)를 대상으로 실시하였다. 설문조사 결과 해기사의 피로도는 충돌, 좌초와 같은 해양사고 유발요인의 하나이며, 항해사와 기관사의 피로도는 서로 차이가 있었다.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1151-1157
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• 2009

Nuclear power plants applying for the continued operation over design life are required to address the effects of reactor water environment in fatigue design requirement of the ASME Code. Reactor water environmental effects are generally evaluated by calculating fatigue correction factors on fatigue usage. This paper describes the application for pressurizer surge line of environmental fatigue correction factors and the strain rate impact in the application. From this paper, the environmental fatigue correction factors resulted from the assumption of a step change in temperature are especially compared with those calculated from the data measured during plant startup. As a conclusion of this paper, the design transient conditions applied to the fatigue design may be conservative in case of the environmental fatigue evaluation.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2159-2166
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• 1996

The stochastic properties of variation in fatigue crack growth are important in reliability and stability of structures. In this study,the stochastic model for the variation of fatigue crack growth rate was proposed in consideration of nonhomogeneity of materials. For this model, experiments were ocnducted on 7075-T6 aluminum alloy under the constant stress intensity factor range. The variation of fatigue crack growth rate was expressed by random variables Z and r based on the variation of material coefficients C and m in the paris-Erodogan's equation. The distribution of fatigue life with respect to the stress intensity factor range was evaluated by the stochastic Markov chain model based on the Paris-Erdogan's equation. The merit of proposed model is that only a small number of test are required to determine this this function, and fatigue crack growth life is easily predicted at the given stress intensity factor range.

• 한국해양공학회지
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• 제5권1호
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• pp.97-105
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• 1991

In this paper, the fatigue strength and the fatigue crack propagation behaviors of the round bar specimens which were spirally built up by welding and subsequently hardened by quenching were investigated. The material used was SF60 which was whdely employed in mechanical components, especially shafts. Fatigue tests were conducted at the fully reversed condition(R=-1) and axial and load control in the room temperature ahd air environment. The experimental results were expressed by both the range of stress intensity factor ($\Delta{K}$) and the effective range of stress intensity factor ($\Delta{K}_{eff}$). It was clarified that applying of quenching after the building up welding process improved the fatigue strength and the gatigue crack propagation property in the low range of $\Delta{K}$ of the built up round bar specimen.

• 한국항만학회지
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• 제11권2호
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• pp.281-294
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• 1997

Fatigue strength analysis is one of the most important themes of ship structure design, as fatigue damages are reported on ship structures even now. But these need basic research workes which will take time. The others are the problem to apply fatigue strength analysis in design and have to be investigated in parallel with basic researches. The one of major items in the latter is the critical damage factor to define with S-N curve for fatigue strength analysis of ship structure design.