• 제목/요약/키워드: FATIGUE

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중년여성의 피로에 영향을 미치는 요인 (Influencing Factors on Fatigue of Middle Aged Women)

  • 장혜경
    • 성인간호학회지
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    • 제22권6호
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    • pp.634-643
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    • 2010
  • Purpose: The purpose of this study was to identify the reported factors influencing fatigue of middle aged women. Methods: Two hundred seven middle aged women between 40 and 59 years of age were recruited from five areas in Korea from March 1, 2010, to April 20, 2010. Data were collected by self-reported questionnaires. Data analysis was done using SPSS/WIN 15.0 program for descriptive statistics, Pearson correlation coefficients and stepwise multiple regression. Results: The average score of fatigue was $2.34{\pm}0.40$. There were significant differences in reported fatigue according to economic status and health status. The reported fatigue was significantly correlated with somatic attribution, psychological attribution, normalizing attribution, depression, marital adjustment, stress, and social support. The major factors that affect fatigue in middle aged women were stress, depression, and normalizing attribution, which explained 32.3% of fatigue. Conclusion: The findings can reduce the fatigue by controlling stress and depression. Additionally, this study can understand the attribution of fatigue in middle aged women. More studies are needed to identify other variables that influence on the fatigue of middle aged women.

국산 저이완 PS 강연선의 피로특성에 관한 연구 (A Study on Fatigue Characteristics of Domestic Low-Relaxation PS Strands)

  • 변근주;송하원;박상순;노병철
    • 콘크리트학회논문집
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    • 제11권6호
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    • pp.113-119
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    • 1999
  • Fatigue failure is a phenomenon such that structures under cyclic service load is failed by sudden brittle manner. Therefore, in order to obtain structures safety against the fatigue failure during their service lifes, fatigue characteristics should be considered for design and analysis of the structures. As stress range of prestressed (PS) tendons, which governs fatigus characteristic of prestressed concrete (PSC) structures, increases with increased use of partial prestressig, it is more necessary to consider fatigue characteristics of PS tendons. In this paper, direct-tension fatigue experiments with special specimen-setting devices are carried out to obtain fatigue characteristics of domestic low relaxation PS strands having different diameters and PS strands connected with coupler. Then, allowable stress range of fatigue for PSC beams using low relaxation strands are presented for the fatigue examination of prestressed concrete beams applied cyclic loading.

A Stochastic Model of Muscle Fatigue in Cyclic Heavy Exertions$\cdots$Formulation

  • Lee, Myun-W.;Pollock, Stephen M.;Chaffin, Don B.
    • 대한산업공학회지
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    • 제5권2호
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    • pp.21-36
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    • 1979
  • Static muscle contractions when prolonged or frequently repeated result in discomfort, fatigue, and musculosketal injuries. An analytic and quantitative model has been developed in order to expand the working knowledge on muscle fatigue. In this paper, three Markov models of muscle fatigue are developed. These models are based on motor unit fatigue-recovery characteristics obtained from information on motor unit behavior as it relates to fatigue and graded exertions. Three successively more realistic models are developed that involve: (1) homogeneous motor units with intensity-dependent fatigue rates and state-independent recovery rates (the HMSI model); (2) homogeneous motor units, intensity-dependent fatigue rates and state-dependent recovery rates (the HMSD model); and (3) non-homogeneous motor units (i.e., Type S and Type F), intensity-dependent fatigue rates and state-dependent recovery rates (the HMSD model). The result indicate that a simple stochastic model provide a means to analyze the complex nature of muscle fatigue in sequential static exertions.

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고강도·고인성 구상흑연주철의 피로한도의 개선 (Improvement of Fatigue Limit in Spheroidal Graphite Cast Iron with High Strength and Toughness)

  • 김민건;김진학
    • 열처리공학회지
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    • 제12권1호
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    • pp.40-46
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    • 1999
  • Rotary bending fatigue tests were carried out to investigate the improvement of fatigue limit in annealed and austempered spheroidal graphite cast iron. Main results obtained are as follows. (1) The tensile strength(hardness) of Series C is higher than that of Series B, and fatigue limits are 245MPa in Series C, 230MPa in Series B and 195MPa in Series A, respectively. (2) The fatigue limits of Series B and Series A are mainly governed by the resistance to fatigue crack initiation. Whereas, the fatigue limit of Series C is governed by the resistance to fatigue crack initiation and growth. The defect size and the resistance to crack initiation and growth should be considered to clarify the fatigue properties in spheroidal graphite cast iron. (3) Improvement of fatigue limit by half-austempering is more reasonable than that of full-austempering treatment in multi defective materials as spheroidal graphite cast iron.

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가압기 밀림관 환경피로평가를 위한 피로보정계수 적용에 관한 연구 (A Study on Application of Fatigue Correction Factor for Environmental Fatigue Evaluation of Pressurizer Surge Line)

  • 양준석;박치용;강선예
    • 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.

틸트 로터 무인항공기의 피로하중 스펙트럼 생성 및 피로해석 (The Development of Fatigue Load Spectrum and Fatigue Analysis for the Tilt Rotor UAV)

  • 임종빈;박영철;박정선;이정진
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회A
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    • pp.654-659
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    • 2007
  • In this paper, the fatigue load spectrum for tilt rotor UAV is developed and fatigue analysis is achieved for flaperon joint. Tilt rotor UAV has two modes which are helicopter mode when UAV is taking off and landing and fixed wing mode when UAV is cruising. To make fatigue load spectrum, FELIX for helicopter mode and TWIST for fixed wing mode are used. And Fatigue analysis of flaperon joint is achieved using fatigue load spectrum we obtained. When S-N test data are analyzed, we use the Kriging meta model to get probability S-N curve for whole range of material life. The result which is life of flaperon joint obtained by suggested fatigue analysis procedure in this paper is compared with that obtained by MSC/Fatigue.

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원공을 가진 CFRP 복합재료의 피로누적손상 및 피로수명에 대한 확률적 해석 (A Probabilistic Analysis for Fatigue Cumulative Damage and Fatigue Life in CFRP Composites Containing a Circular Hole)

  • 김정규;김도식
    • 대한기계학회논문집
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    • 제19권8호
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    • pp.1915-1926
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    • 1995
  • The Fatigue characteristics of 8-harness satin woven CFRP composites with a circular hole are experimentally investigated under constant amplitude tension-tension loading. It is found in this study that the fatigue damage accumulation behavior is very random and history-independent, and the fatigue cumulative damage is linearly related with the mean number of cycles to a specified damage state. From these results, it is known that the fatigue characteristics of CFRP composites satisfy the basic assumptions of Markov chain theory and the parameter of Markov chain model can be determined only by mean and variance of fatigue lives. The predicted distribution of the fatigue cumulative damage using Markov chain model shows a good agreement with the test results. For the fatigue life distribution, Markov chain model makes similar accuracy to 2-parameter Weibull distribution function.

크랭크스로 단조강의 피로수명의 확률분포 추정 (Estimation of Probability Distribution of Fatigue Lives in Crank Throw Forged Steel)

  • 김선진;안석환
    • 동력기계공학회지
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    • 제20권3호
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    • pp.29-35
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    • 2016
  • Because of the severe service environment of the large marine vessel, the fatigue strength and its evaluation play an important role in design and maintenance of marine crankshaft. The aim of this work is to investigate the probability distribution of fatigue lives in crank throw forged steel and to develop the methodology for estimation of the probabilistic design fatigue strength. Detailed studies were performed on the constant amplitude axial loading fatigue test. The experiments were controlled by stress ratio of -1 and 15Hz frequency for each stress level. The considerable variability of fatigue life was observed in each stress level under rigidly controlled constant fatigue testing conditions. The fatigue life of crank throw forged steel was well followed the log-normal and Weibull distribution. In addition, it can be used for the estimation of probabilistic design fatigue strength by using the proposed methodology.

파로설계에 관한 소고 (A Study on the Design against Metal Fatigue)

  • 이순복
    • 한국기계연구소 소보
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    • 제4권1호
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    • pp.19-26
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    • 1981
  • Fatigue, the birth and growth of cracks in metal parts subjected to repeated loading, has been a problem plaguing engineers since the Industrial Revolution and the advent of rotating or reciprocating machinery. Designing against metal fatigue was studied briefly in several aspects. Examples of fatigue failures were shown. Fatigue was classified by loading: uniaxial Fatigue, multiaxial fatigue, cumulative fatigue da¬mage. Fatigue design criteria were discussed: Infinite-Life Design, Safe-Life Design, Fail-Safe Design, and Damage Tolerant Design. Mitigation of notch effects by design, improvement of fatigue strength of metal parts by residual stress and surface finishing were discussed. Relative fatigue beha¬vior was studied under various environmantal conditions. Especially the effects of corrosion, temperature, fretting, and irradiation were covered.

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음향방출법을 이용한 스테인레스강 피로수명 예측 (Fatigue Life Prediction of Stainless Steel Using Acoustic Emission)

  • 김용환;정창규;양유창;한경섭
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.193-198
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    • 2001
  • The feasibility of the acoustic emission technique in predicting the residual fatigue life of STS304 stainless steel is presented. Acoustic emission was continuously monitored during the fatigue tests. Considerable acoustic emission occurred during the first few cycles. Acoustic Emission increased rapidly at about 90% of the fatigue life, clear and ample warning of impending fatigue failure was observed. Fatigue damage accumulation was evaluated in terms of an AE cumulative counts. The AE cumulative counts may be taken as an indicator of fatigue cumulative damage. Fatigue damages corresponding to 20, 40, 60 and 80% of the total life were induced at a cyclic stress amplitude. The specimens with and without fatigue damage were subjected to tensile tests. In tensile tests, the total cumulative counts were reduced with increasing fatigue damage. It was observed that the residual tensile strength of material did not change significantly with prior cyclic loading damages.

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