• Title/Summary/Keyword: Fatigue

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Review of the Prevalence of Chronic Fatigue Worldwide

  • Son, Chang-Gue
    • The Journal of Korean Medicine
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    • v.33 no.2
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    • pp.25-33
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    • 2012
  • Objectives: To obtain the features of prevalence of chronic fatigue and chronic fatigue syndrome worldwide. Methods: All research reports for prevalence of chronic fatigue and chronic fatigue syndrome were selected from PubMed, KMbase and KISS database, and the prevalence were analyzed according to the symptoms and countries. Results: A total of 39 articles from 13 other countries and 4 articles from Korea met the criteria of this study. The prevalence of chronic fatigue and chronic fatigue syndrome was about 10% and 1% respectively. The prevalence for Korean was 17.7% and 1.4% respectively, however the data have a limitation due to the lack of well-designed studies. Conclusions: This report can provide essential information to build a strategy for development of therapeutics against chronic fatigue and chronic fatigue syndrome using traditional Korean medicine.

A Study on the Prediction of Fatigue Damage in 2024-T3 Aluminium Alloy Using Neural Networks (신경회로망을 이용한 AI 2024-T3합금의 피로손상예측에 관한 연구)

  • Cho, Seok-Swoo;Jang, Deuk-Yul;Joo, Won-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.7
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    • pp.168-177
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    • 1999
  • Fatigue damage is the phenomena which is accumulated gradually with loading cycle in material. It is represented by fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$. Fracture mechanical parameters estimating large crack growth behavior can calculate quantitative amount of fatigue crack growth resistance in engineering material. But fatigue damage has influence on various load, material and environment. Therefore, In this study, we propose that artificial intelligent fatigue damage model can predicts fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$ simultaneously using fracture mechanical and nondestructive parameters.

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A Study on Fatigue Life and Fatigue Crack Propagation Behavior of MMC (MMC의 피로수명과 피로균열전파거동에 관한 연구)

  • 허선철;박원조;최용범
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.12
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    • pp.127-133
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    • 2002
  • The objective of this study is to investigate fatigue life and fatigue crack propagation behavior The experiment of fatigue life for MMC have been carried out for the stress ratio R=0.1 at 20Hz. Fatigue lift limit of AC4CH alloy is about 70 ㎫ and Fatigue limit of MMC has been increment to 120 ㎫, therefore, fatigue limits of MMC is about 71 % higher than that of AC4CH alloy Crack propagation tests on half-size CT specimen of thickness 12.5mm were conducted by using sinusoidal waveform. The crack length was monitored by compliance method. Test conditions were at 0.1 and 0.05 of load ratio at 10Hz of loading frequency and test load was 2.3kN. The effects of stress ratio on the fatigue crack propagation behavior for MMC was discussed within the Paris law. As the results of this study, Fatigue crack propagation increased with increasing the load ratio.

Prediction and Application of Fatigue Life on Characteristics of Fatigue Crack Propagation of Thin Sheet Alloy (박판합금재료의 피로균열 전파특성에 대한 피로수명예측과 활용)

  • Lee, Ouk-Sub;Kim, Seung-Gwon
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.2 s.191
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    • pp.103-109
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    • 2007
  • In fatigue life prediction, it is important that fatigue life is affected by crack closure phenomenon in thin sheet Al alloy. In this research, we attempt to (1)analyze the characteristics of fatigue crack propagation in constant loading condition for thin sheet Al 2024-T3 alloy which is generally used in transportation structures, (2)identify the crack closure phenomenon in thin sheet comparing experimental results of thin and thick sheet specimen under same fatigue loading condition. In using the fatigue related material constants from these fatigue crack propagation analysis, we attempt to (3)operate the fatigue life estimating process with considering crack closure phenomenon and (4)analyze the experimental and prediction results of fatigue life in thin sheet Al alloy.

A Survey on the Relationship between the Fatigue due to Schoolwork and Dietary (식품섭취(食品攝取)와 학업피로(學業疲勞)의 관계(關係)에 대(對)한 조사(調査))

  • Lee, Dong-Suk
    • Korean Journal of Food Science and Technology
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    • v.6 no.3
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    • pp.158-162
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    • 1974
  • The writer has undertaken a survey, against 467 urban university women students, of the fatigue due to their schoolwork and has intended to clarify the relationship between the fatigue and dietary. As a result, the following described conclusion was obtained: (1) The fatigue due to their schoolwork was found in an order of mental fatigue >physical fatigue> neuro-sensory fatigue among which their schoolwork was proved as a typical mental works. (2) It was found, in comparison of the health condition with the fatigue from schoolwork, that the frequencies of mental and neurosensory fatigue in which physical fatigue is excluded had a significant difference. (3) In an analysis of the fatigue rate in relation with the daily dietary, it was found that fatigue rate of the group which takes meat, egg, fish and milk every day showed a significantly lower rate over the group which takes these food occasionally.

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ASSESSMENT OF THERMAL FATIGUE IN MIXING TEE BY FSI ANALYSIS

  • Jhung, Myung Jo
    • Nuclear Engineering and Technology
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    • v.45 no.1
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    • pp.99-106
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    • 2013
  • Thermal fatigue is a significant long-term degradation mechanism in nuclear power plants. In particular, as operating plants become older and life time extension activities are initiated, operators and regulators need screening criteria to exclude risks of thermal fatigue and methods to determine significant fatigue relevance. In general, the common thermal fatigue issues are well understood and controlled by plant instrumentation at fatigue susceptible locations. However, incidents indicate that certain piping system Tee connections are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentations. Therefore, in this study thermal fatigue evaluation of piping system Tee-connections is performed using the fluid-structure interaction (FSI) analysis. From the thermal hydraulic analysis, the temperature distributions are determined and their results are applied to the structural model of the piping system to determine the thermal stress. Using the rain-flow method the fatigue analysis is performed to generate fatigue usage factors. The procedure for improved load thermal fatigue assessment using FSI analysis shown in this study will supply valuable information for establishing a methodology on thermal fatigue.

Retardation Behavior of Fatigue Crack Growth and Fatigue Life Prediction of Thin Sheet Al 2024-T3 Alloy (박판 Al 2024-T3 합금재료의 피로균열성장지연거동과 피로수명예측)

  • Kim, S.G.
    • Journal of the Korean Society of Mechanical Technology
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    • v.13 no.2
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    • pp.31-37
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    • 2011
  • Sheet aluminum alloys have been used in manufacturing of machine structures. In fatigue crack propagation behavior of thin sheet aluminum alloys, it is important that fatigue crack growth rate is affected by crack closure phenomenon. In this work, we analyzed the characteristics of fatigue crack propagation behavior in experiment of constant stress condition for thin sheet Al 2024-T3 alloys, and identified the retardation behavior of crack growth by comparing experimental results of thin and thick plate specimen. We attempt to operate the fatigue life estimating process using the fatigue related material constants from referred fatigue crack propagation analysis. And we analyzed the experimental and prediction results of fatigue life of thin sheet aluminum alloy in order to identify the relation between retardation behavior of fatigue crack growth and crack closure phenomenon.

Characteristics of Fatigue in Sasang Constitution by Analyzing Questionnaire and Medical Devices Data (설문지와 의료기기 자료 분석을 통한 사상체질별 피로 특성 연구)

  • Kim, Koo;Ha, Ye-Jin;Park, Soo-Jeong;Choi, Na-Rae;Lee, Young-Seop;Joo, Jong-Cheon
    • Journal of Sasang Constitutional Medicine
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    • v.25 no.4
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    • pp.306-319
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    • 2013
  • Objectives The purpose of this study was to find correlations between gastrointestinal disorders, pain, sleep disorder, fatigue, and to figure out characteristics of fatigue in Sasang Constitution using medical devices data. Methods Sixty three subjects were divided into fatigue group and non-fatigue group, both groups had to undergo blood tests, questionnaire, Sasang constitutional analysis tool (SCAT), pulse wave analyzer examination, heart rate variability examination, nail fold capillary microscopic examination. Results 1) The results of questionnaire about fatigue, gastrointestinal disorder, pain, sleep disorder, quality of life had significant differences between fatigue and non-fatigue groups. 2) Soeumin had more serious gastrointestinal problem and Soyangin had more serious sleep disorder in fatigue groups than non-fatigue groups. 3) According to blood test results, there was no difference between fatigue and non-fatigue groups. 4) Elastic parameter of pulse wave analyzer and nail fold capillary microscopic examination showed significant differences between fatigue and non-fatigue groups in Soyangin. Conclusions We reach the conclusion that fatigue is usually accompanied by gastrointestinal disorder, pain, sleep disorder, deterioration in the quality of life. In Soeumin, treating gastrointestinal disorders can be helpful for treatment of fatigue. In Soyangin, improving sleep disorder may be more effective way to treat fatigue.

Fatigue and its Related Factors in Patients on Hemodialysis (혈액투석환자의 피로와 관련 요인에 관한 연구)

  • 김혜령
    • Journal of Korean Academy of Nursing
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    • v.26 no.1
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    • pp.53-72
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    • 1996
  • The Purpose of this study was to identify characteristics of fatigue and the relationship between fatigue and related factors in patients on hemodialysis. This study was a survey study using a cross-sectional design. The subjects for this study were 101 patients on hemodialysis who were registered in the six hemodialysis clinics among a total of eleven clinics in Seoul. The period of data collection was from February 28, 1995 to May 2, 1995. Data were collected through an interview with a structured packet and the physiological data. The tools used in this study were the Visual Analogue Scale-Fatigue developed by Lee et al(1990) and translated by Lee(1991), the fatigue interview schedule developed by this researcher, Zung's self rating depression scale(Zung, 1965), the self-efficacy scale developed by Sherer et al(1982) and the Norbeck Social Support Questionnaire(NSSQ) translated by Oh(1984). The collected data were analyzed using descriptive statistics(mean, standard deviation, frequency, range), Pearson correlation coefficients and Stepwise multiple regression. The results were as follows ; 1. Characteristics of Fatigue of hemodialysis patients : 1) 79 of 101 hemodialysis patients complained fatigue. 2) The mean fatigue score as measured by the VAS-F was 36.2mm. 3) The mean duration of fatigue was 2.9 hours 2. Characteristics of fatigue related factors : 1) The physiologic factor which included Hgb, Hct, BUN, creatinine, potassium and interdialytic weight gain deviated from normal range. 2) The psychological factor which included depression and self-efficacy was about the same level as for patients with other chronic diseases. 3) The environmental factor which included social support had wide variation. 3. The relationship between fatigue and related factors : 1) Interdialytic weight gain in the physiologica factor was the only valuable with fatigue (p<.05) 2) The relationship between fatigue and the psychological factor of depression showed a positive and strong correlation(p<.05). According to the findings of this study, fatigue was highly correlated with the depression. This indicates that nurses should try to assess and control psychological factors when patients complain of fatigue rather than just considering physiological factors. Nursing has to develop effective nursing interventions to reduce fatigue in patients with chronic diseases using the relationship between fatigue and physiological, psychological and environmental factors.

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Thermal-mechanical Fatigue Life Prediction of 12Cr Forged Steel Using Strain Range Partitioning method (변형률분할법에 의한 12Cr 단조강의 열피로 수명예측)

  • 하정수;옹장우;고승기
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1192-1202
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    • 1994
  • Fatigue behavior and life prediction were presented for thermal-mechanical and isothermal low cycle fatigue of 12Cr forged steel used for high temperature applications. In-phase and out-of-phase thermal-mechanical fatigue test at 350 to 600.deg. C and isothermal low cycle fatigue test at 600.deg. C were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Cyclic softening behavior was observed regardless of thermal-mechanical and isothermal fatigue tests. The phase difference between temperature and strain in thermal-mechanical fatigue resulted in significantly shorter fatigue life for out-of-phase than for in-phase. The difference in fatigue lives was dependent upon the magnitudes of inelastic strain ranges and mean stresses. Increase in inelastic strain range showed a tendency of intergranular cracking and decrease in fatigue life, especially for out-of-phase thermal-mechanical fatigue. Thermal-mechanical fatigue life prediction was made by partitioning the strain ranges of the hysteresis loops and the results of isothermal low cycle fatigue tests which were performed under the combination of slow and fast strain rates. Predicted fatigue lives for out-of-phase using the strain range partitioning method showed an excellent agreement with the actual out-of-phase thermal-mechanical fatigue lives within a factor of 1.5. Conventional strain range partitioning method exhibited a poor accuracy in the prediction of in-phase thermal-mechanical fatigue lives, which was quite improved conservatively by a proposed strain range partitioning method.