• Title, Summary, Keyword: Fatigue

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Mothers Perception of Fatigue in Postpartum Period (산욕기 어머니가 자각하는 피로)

  • Kim, Shin-Jeong;Jeong, Geum-Hee;Kim, Eun-Ha
    • Korean Journal of Women Health Nursing
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    • v.7 no.4
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    • pp.461-472
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    • 2001
  • A study was done to identify mothers' perception of fatigue in postpartum period. Questionnaires were collected from 267 normal postpartum mothers in Korea from July to December 2000. The questionnaires used to measure mothers' fatigue were "Subjective Symptoms of Fatigue Test" designed by Research Committee of Industrial Fatigue in Hygienic Association of Japan Industry. The collected data were analyzed by SPSS-Win. The results revealed that The average fatigue score of subjects was 1.70; Physical fatigue had the highest value with a mean of 1.89, followed by psychological fatigue with a mean score of 1.62, neuro-sensory fatigue was rated lowest with a mean of 1.58. Sorting out the subjects fatigue level per a week during Sweeks, 6th week after postpartum had the highest value with a mean of 1.85. Degree of fatigue was also compared with the respect to the general characteristics of mothers: There were statistically significant differences according to mothers' job (t=-2.021, p=.046), sleeping time (t=2.771, p=.006), having a nap (t=-2.132, p=.034), baby character (F=3.089, p=.047), baby sex (t=-2.054, p=.041), having a person who help domestic affairs (t=2.292, p=.023). Therefore variable nursing intervention should be provided to alleviate the fatigue according to the postpartum period. Especially the nursing intervention program to alleviate the physical fatigue is needed.

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Environmental Fatigue Evaluation for Thermal Stratification Piping of Nuclear Power Plants (열성층을 포함하는 원자력발전소 배관의 환경피로평가)

  • Kim, Taesoon;Kim, Kyuhyung
    • Journal of the Korean Society of Safety
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    • v.33 no.5
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    • pp.164-169
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    • 2018
  • A detailed fatigue evaluation procedure was developed to mitigate the excessive conservativeness of the conventional environmental fatigue evaluation method for the pressurizer spray line elbow of domestic new nuclear power plants. The pressurizer spray line is made of austenitic stainless steel, which is relatively sensitive to the environmentally assisted fatigue, and has a low degree of design margin in terms of environmentally assisted fatigue due to the thermal stratification phenomenon on the pipe cross section as a whole or locally. In this study, to meet the environmental fatigue design requirements of the pressurizer spray line elbow, the new environmental fatigue evaluation has been performed, which used the ASME Code NB-3200-based detailed fatigue analysis and the environmental fatigue correction factor instead of the existing NB-3600 evaluation method. As a result, the design requirements for environmentally assisted fatigue were met in all parts of the pressurizer spray line elbow including the fatigue weakened zones by thermal stratification.

Fatigue properties of welded joints for TMCP steels (TMCP 고장력강 용접부의 피로 특성에 관한 연구)

  • 임채범;권영각;엄기원
    • Journal of Welding and Joining
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    • v.8 no.2
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    • pp.40-52
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    • 1990
  • Fatigue behavior of the AH, DH and EH grade TMCP(Thermo-Mechanical Control Process) steels was studied. High cycle and low cycle fatigue tests were carried out for the weldment and base metal of each steel. The results showed that the fatigue limit at 2 * $10^6$ cycles was 33 to 37 kg/$mm^2$ for the base metal and 30 to 34 kg/$mm^2$ for the weldment. The ratio of fatigue limit to tensile strength for TMCP steels was 0.65 to 0.71, which was a value close to the upper limit for the ordinary steels. It was also found that the high cycle fatigue behavior of TMCP steels could be affected by the microstructures of base metal. It will be necessary to have fine structure for TMCP steels to increase the fatigue resistance. In low cycle fatigue test, the fatigue lifetime of AH and DH steels accorded well with the ASME best fit curve, while that of EH steel was considerably lower than the fatigue lifetime of the other steels. Fatigue resistance of the weldment made by high heat input(180kJ/cm) welding was not lower than that made by low heat input(80kJ/cm) welding in case of high cycle fatigue, but the high heat input welding decreased the fatigue resistance in case of low cycle fatigue.

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Fatigue in Pediatric Patients with Cancer (소아청소년 암환자의 피로)

  • Lee, Jung-Won;Park, Ho-Ran
    • Child Health Nursing Research
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    • v.16 no.1
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    • pp.66-72
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    • 2010
  • Purpose: This study was done to identify factors associated with fatigue in pediatric patients with cancer in order to develop nursing interventions for this population. Methods: The participants were 95 pediatric cancer patients admitted to a university medical center in Seoul, Korea, and 95 parents. The $PedsQL^{TM}$, Multidimensional Fatigue Scale developed by Varni (2002) was used to measure fatigue. Data were analyzed with the SAS program and t-test, analysis of variance (ANOVA), Pearson correlation coefficients, and multiple regression were used to identify the association of factors with fatigue. Results: The mean score for fatigue was 30.42 in the pediatric cancer patients and 34.77 in the parents. Fatigue was higher in patients living with a single parent, in patients whose father had a lower education and those patients with a fever. Pain, frequency and intensity of nausea and vomiting, depression, anxiety, and disruption of usual activity were positively associated with fatigue. The predictive factors for fatigue were disruption of usual activity, depression and living with or without parents. Conclusion: Pediatric patients with cancer experienced fatigue during their diagnosis and treatment. Of the multiple factors associated with fatigue, the association between disruption of usual activity and fatigue was the highest indicating a need to be concerned with this factor when providing interventions to alleviate fatigue.

Reliability and Validity of Turkish Versions of the Child, Parent and Staff Cancer Fatigue Scales

  • Gerceker, Gulcin Ozalp;Yilmaz, Hatice Bal
    • Asian Pacific Journal of Cancer Prevention
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    • v.13 no.7
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    • pp.3135-3141
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    • 2012
  • This study was designed to adapt the Turkish versions of scales to evaluate fatigue in children with cancer from the perspectives of the children, parents and staff. The objective of this study was to validate "Child Fatigue Scale-24 hours" (CFS-24 hours), "Parent Fatigue Scale-24 hours" (PFS-24 hours) and "Staff Fatigue Scale-24 hours" (SFS-24 hours) for use in Turkish clinical research settings. Translation of the scales into Turkish and validity and reliability tests were performed. The validity of the translated scales was assessed with language validity and content validity. The reliability of the translated scales was assessed with internal consistency. The scales were evaluated by considering the following: calculation of the Cronbach alpha coefficient for parallel form reliability with 52 pediatric cancer patients, 86 parents and 43 nurses. The internal consistency was estimated as 0.88 for the Child Fatigue Scale-24 hours, 0.77 for the Parent Fatigue Scale-24 hours, and 0.72 for the Staff Fatigue Scale-24 hours (Cronbach's ${\alpha}$). The Turkish version of the Child Fatigue Scale -24 hours, the Parent Fatigue Scale -24 hours and the Staff Fatigue Scale -24 hours were judged reliable and valid instruments to assess fatigue in children and showed good psychometric properties. These scales should assist in understanding to what extent initiatives can minimize or eliminate fatigue. Our scales are recommended for further studies and use in pediatric oncology clinics as routine measurements and nursing initiatives should be planned accordingly.

Characteristics of Fatigue Crack Propagation and Fatigue Life Prediction of Thin Sheet Al Alloy (박판 Al 합금재료의 피로균열전파특성과 피로수명예측)

  • Kim, Seung-Gwon;Lee, Ouk-Sub;Yang, Heang-Ryeal;Yeo, In-Cheol;Park, Sung-Wan
    • Proceedings of the KSME Conference
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    • pp.356-361
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    • 2008
  • In characteristics of fatigue crack propagation, it is important that fatigue life is affected by crack closure phenomenon in thin sheet Al alloy. The purpose of this paper is to analyze the characteristics of fatigue crack propagation in constant loading condition for sheet Al 2024-T3 alloy of two sort of thickness and identify the difference of fatigue life in thin sheet specimen comparing experimental results of thin sheet specimen and relatively thick sheet specimen under same fatigue loading condition. In applying fatigue related material constants from fatigue crack propagation analysis, we attempt to operate the fatigue life estimating process of thin sheet specimen by modified Paris‘ law considering crack closure phenomenon and analyze the experimental and prediction results of fatigue life in thin sheet Al alloy.

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Study on stiffness deterioration in steel-concrete composite beams under fatigue loading

  • Wang, Bing;Huang, Qiao;Liu, Xiaoling;Ding, Yong
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.499-509
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    • 2020
  • The purpose of this paper is to investigate the degradation law of stiffness of steel-concrete composite beams after certain fatigue loads. First, six test beams with stud connectors were designed and fabricated for static and fatigue tests. The resultant failure modes under different fatigue loading cycles were compared. And an analysis was performed for the variations in the load-deflection curves, residual deflections and relative slips of the composite beams during fatigue loading. Then, the correlations among the stiffness degradation of each test beam, the residual deflection and relative slip growth during the fatigue test were investigated, in order to clarify the primary reasons for the stiffness degradation of the composite beams. Finally, based on the stiffness degradation function under fatigue loading, a calculation model for the residual stiffness of composite beams in response to fatigue loading cycles was established by parameter fitting. The results show that the stiffness of composite beams undergoes irreversible degradation under fatigue loading. And stiffness degradation is associated with the macrobehavior of material fatigue damage and shear connection degradation. In addition, the stiffness degradation of the composite beams exhibit S-shaped monotonic decreasing trends with fatigue cycles. The general agreement between the calculation model and experiment shows good applicability of the proposed model for specific beam size and fatigue load parameters. Moreover, the research results provide a method for establishing a stiffness degradation model for composite beams after fatigue loading.

A review of fatigue failures in LWR plants in Japan

  • Kunihiro, Iida
    • Proceedings of the KWS Conference
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    • pp.19-34
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    • 1996
  • A review was made of fatigue failures of nuclear power plant components in Japan, which were experienced in service and during periodical inspection. No case has been recently reported of a service fatigue failure of a reactor pressure vessel itself, excluding nozzle corner cracks, that occurred many years ago. But, service fatigue failures have been occasionally experienced in piping systems, pumps, and valves, on which fatigue design seems to have been inadequately applied. The causes of fatigue failures can be divided into two categories: mechanical-vibration-induced fatigue and thermal-fluctuation-induced fatigue. Vibration-induced fatigue failure occurs more frequently than is generally thought. The lesson gleaned from the present survey is a recognition that a service fatigue failure may occur due to any one or a combination of the following factors: (1) lack of communication between designers and fabrication engineers, (2) lack of knowledge about a possibility of fatigue failure and poor consideration about the effects of residual stresses, (3) lack of consideration on possible vibration in the design and fabrication stages, and (4) lack of fusion or poor penetration in a welded joint.

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

  • Lee, Sun-Bok
    • 한국기계연구소 소보
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    • v.4 no.1
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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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Fatigue Life Prediction of Stainless Steel Using Acoustic Emission (음향방출법을 이용한 스테인레스강 피로수명 예측)

  • Kim, Y.H.;Jung, C.K.;Yang, Y.C.;Han, K.S.
    • Proceedings of the KSME Conference
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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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