• Title/Summary/Keyword: Fatigue Behavior

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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.

The Influence of the Small Circular Hole Defect on the Fatigue Crack Propagation Behavior in Aluminum Alloys (알루미늄 합금재의 피로크랙 전파거동에 미치는 미소원공결함)

  • Kim, G.H.;Lee, H.Y.
    • Journal of Advanced Marine Engineering and Technology
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    • v.32 no.6
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    • pp.834-840
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    • 2008
  • We carried out fatigue testing with materials of aluminum alloyC7075-T6, 2024-T4) by rotary bending fatigue tester. We investigated fatigue limit, fatigue crack initiation, fatigue crack propagation behavior and possibility of fatigue life prediction to the different small circular hole defect. The summarized result are as follows; Fatigue limit of the smooth specimens were related tensile strength and yield strength. In case of more large applied stress and small circular hole crack defect, the fatigue crack was grown rapidly. The fatigue crack propagation behavior proceed at according to inclusion. Fatigue crack propagation ratio appeared instability and retardation phenomenon in the first half of fatigue life but appeared stability and replied in the latter half. On other hand, this experimental data of the materials are appeared fatigue life predictability.

Factors Influencing Perceived Fatigue and Health Promotion Behavior among Hair Dressers (미용사의 지각된 피로도와 건강증진행위에 영향을 미치는 요인)

  • Lee, Mi-Ja;Han, Sam-Sung;Yoo, Wang-Keun
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.28 no.4
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    • pp.374-381
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    • 2018
  • Objective: This study was carried out to examine the factors affecting the fatigue and health promotion behavior of hairdressers and their respective levels. The data were collected from 195 hairdressers working in beauty shops in Daegu and Gyeongsangbuk-do Province using self-administered questionnaires over the period from July 1 to July 31. Methods: A multiple regression model was used to study the factors influencing fatigue and health promotion behavior among hairdressers. Results: This study showed a statistically significant difference in perceived fatigue levels and health promotion behavior according to age, family type, education level, work period, work position, and fatigue level in the past one week. In addition, multiple regression showed that statistically significant factors affecting perceived fatigue were education level, work period, and fatigue level in the past one week. Statistically significant factors affecting health promotion behavior were age and fatigue level in the past one week. The level of perceived fatigue among hairdressers tended to be higher than other workers, and their level of practice of health promotion behavior was generally lower. Conclusions: The improvement of the work environment, such as through the distribution of a proper workload considering workers' characteristics and strengthening of exercise programs to reduce the fatigue level and promote health practices among hairdressers is needed.

Fatigue and Fatigue-Regulation Behaviors of Undergraduates in Courses Related to Public Health and Undergraduates in Courses not Related to Public Health (보건계열 대학생과 비보건계열 대학생의 피로와 피로조절행위)

  • Choi, Jung
    • Journal of Korean Academy of Fundamentals of Nursing
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    • v.16 no.1
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    • pp.83-91
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    • 2009
  • Purpose: The purpose of this study was to compare fatigue and fatigue-regulation behaviors in undergraduates courses related to public health (group A) and undergraduates in courses not related to public health (group B). Method: Using a structured questionnaire, data were collected from 236 undergraduates. Descriptive statistics, Pearson correlation coefficient, t-test with SAS package were used for data analysis, Results: There was a statistically significant difference between group A and group B in t-test comparison by group for fatigue, and all subcategories of fatigue and fatigue-regulation behaviors. The frequency of fatigue-regulation behavior of group A was 12.23 and the mean for total efficiency of fatigue-regulation behavior was 2.17, while the frequency of fatigue-regulation behavior for group B was 10.47 and the mean for total efficiency of fatigue-regulation behavior was 1.75. Finally, total fatigue and all subcategories of fatigue were positively related to fatigue-regulation behaviors. Conclusion: It is necessary to develop an intervention program for regulating fatigue in undergraduates courses related to public health.

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The Fatigue Behavior of Laser Weldment in Heterogeneous Materials (이종재료 레이저 용접부의 피로거동)

  • 권응관;오택열;곽대순;이종재
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.759-764
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    • 1997
  • In this study, Fatigue behavior of laser weldment in heterogeneous materials was investigated. Fatigue strength test and fatigue crack propagation test were performed for specimens with laser weldment in heterogeneous materials, and hardness test was performed. From the fatigue strength test. it was observed that the difference of strength between heterogeneous materials had eflect on crack initiation position and fatigue limit. From the fatigue crack propagation test. it was observed that fatigue behavior of laser weldment in heterogeneous materials is different from that in same materials. The difference of strength between heterogeneous materials and laser weldment had effect on fatigue crack propagation rate.

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Effects of Fatigue on Health Promotion Behavior and Mental Health of Automotive Manufacturing Workers (자동차부품 생산직 근로자의 피로도가 건강증진행위와 정신건강에 미치는 영향)

  • Lee, Kyung-Hee;Lee, Kyung-Sook
    • Korean Journal of Occupational Health Nursing
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    • v.20 no.2
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    • pp.143-152
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    • 2011
  • Purpose: This study investigated to relationship of fatigue, health promotion behavior and mental health in automotive manufacturing workers. Methods: As a descriptive research design, the data were collected from 198 workers in a city. It was analyzed using the SPSS/WIN 12.0. Results: The level of fatigue was beyond moderate, health promotion behavior was low, mental health was slightly unhealthy. The fatigue was significantly correlated with health promotion behavior. The global fatigue, job satisfaction and drinking explained 22.3% of health promotion behavior. Conclusion: It is necessary for the automotive manufacturing workers and their companies to reduce level of fatigue and mental health and to increase level of health promotion behavior.

Fatigue and Fatigue-regulation Behavior in Hemodialysis Patients (혈액투석 환자의 피로와 피로조절행위)

  • Kim, Hye-Won
    • Journal of Digital Convergence
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    • v.10 no.5
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    • pp.301-305
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    • 2012
  • This study was performed to examine the relationship between fatigue and fatigue-regulation behavior in Hemodialysis(HD) patients. Methods: The subjects for this study were 107 patients on HD who were registered in a hospital in Seoul. The data were collected from August 2 to August 14, 2010. The collected data were analyzed by the SPSS WIN 12.0 program. Results: The mean score of fatigue was 77.1 which means their experience of high level fatigue. Frequency of the fatigue-regulation behavior and the mean of efficiency of the fatigue-regulation behavior was 8.8 and 22.8. Positive correlation was found between fatigue and fatigue-regulation behavior (r=.45, p=.000). Conclusion: It is considered that the study emphasizes for the healthcare providers to recognize fatigue as the important nursing issue for HD patients. And it is necessary to develop an evidence-based nursing intervention program for regulating fatigue in HD patients.

Analysis of Relationship Between Job Stress and Fatigue According to The Type A/B Behavior Pattern of Physical Therapists

  • Wang, Joong San
    • Journal of International Academy of Physical Therapy Research
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    • v.8 no.2
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    • pp.1135-1141
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    • 2017
  • Stress and fatigue are general physical aspects of our daily lives. It has been shown that physical therapists have different levels of job stress and fatigue according to the type A/B behavior patterns. This study collected data from 212 physical therapists between October 28 and November 23, 2016 using an anonymous, self-administered questionnaire. The study results showed the proportion of physical therapists with the Type A behavior patterns(TABP) was 18% greater than that of physical therapists with the Type B behavior patterns(TBBP). In this study, physical therapists with TABP were compared with physical therapists with TBBP. The results indicated that physical therapists with TABP were more inclined to experience higher levels of overall job stress and fatigue from the following stress factors: physical environment, job requirement, and job autonomy. Therefore, the stronger the tendency toward TABP, the stronger the feeling of job stress and fatigue from physical environment, job requirement, and job autonomy. Those with a tendency toward TBBP showed positive correlations between job requirement and the total job stress score; thus, the stronger the tendency toward TBBP, the stronger the feeling of overall job stress and fatigue from job requirement. This study suggests that it is necessary to manage the job stress and fatigue of physical therapists with both TABP and TBBP and to manage the job stress and fatigue of physical therapists with the type A behavioral pattern.

Prediction of Fatigue Crack Propagation Life under Constant Amplitude and Overloading Condition (일정진폭 및 과대하중 하에서의 피로 균열 성장 수명 예측)

  • 이억섭;김승권
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.10
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    • pp.113-119
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    • 1998
  • Ship structures and aircraft structures are consisted of thin sheet alloy, so it is very important to understand the characteristics of fatigue crack propagation of that material and to establish the data base. The data for fatigue crack propagation behavior scatter very much even under identical experimental conditions with constant loading. The behavior of fatigue crack propagation under regular and irregular cyclic loadings is known to be highly affected by complicated factors such as plastic zone developed at the vicinity of crack tip and reduction of cross sectional area. In this paper, the controlled stress amplitude and overload fatigue crack propagation tests have been conducted to investigate the effect of varying factors such as plastic zone size near the crack tip and area reduction factor (AF) on the fatigue crack propagation behavior A better simulation of fatigue crack propagation behavior is found to be obtainable by using Wheeler and Willenborg models with AF effect.

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Fatigue Assessment Model of Corroded RC Beams Strengthened with Prestressed CFRP Sheets

  • Song, Li;Hou, Jian
    • International Journal of Concrete Structures and Materials
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    • v.11 no.2
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    • pp.247-259
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    • 2017
  • This paper presents a fatigue assessment model that was developed for corroded reinforced concrete (RC) beams strengthened using prestressed carbon fiber-reinforced polymer (CFRP) sheets. The proposed model considers the fatigue properties of the constituent materials as well as the section equilibrium. The model provides a rational approach that can be used to explicitly assess the failure mode, fatigue life, fatigue strength, stiffness, and post-fatigue ultimate capacity of corroded beams strengthened with prestressed CFRP. A parametric analysis demonstrated that the controlling factor for the fatigue behavior of the beams is the fatigue behavior of the corroded steel bars. Strengthening with one layer of non-prestressed CFRP sheets restored the fatigue behavior of beams with rebar at a low corrosion degree to the level of the uncorroded beams, while strengthening with 20- and 30%-prestressed CFRP sheets restored the fatigue behavior of the beams with medium and high corrosion degrees, respectively, to the values of the uncorroded beams. Under cyclic fatigue loading, the factors for the strengthening design of corroded RC beams fall in the order of stiffness, fatigue life, fatigue strength, and ultimate capacity.