• Korean Journal of Rural Living Science
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• v.3
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• pp.45-52
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• 1992

• Journal of Korean Academy of Nursing
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• v.2 no.1
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• pp.87-96
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• 1971

This Study was undertaken to evaluate the present health status and fatigue of the workers in T. Industrial Company in Pusan in Jan. 1971. The results were based on a question are from 354 working girls. The results of this study are as follows: 1. The largest portion of the workers, 20.2% of the questioned employees, were observed to lie at age 20. 2. Regarding their formal education, 76.0% of them had completed middle school. while only 7. 1% had graduated from high school, . 3. 63.0% receive 7-8 hrs. of sleep a day while 18.4% receive S-6 hrs. of sleep a day. 4. 36.4% spend leisure time reading: while 15.5% spend it resting and thinking. 5. 53.8% of them live in the company′s dormitory and 31.6% live at home. 6. Time spent in travel to work: 32.8% spent 40-49 min., 23.6% spent 10-29 min. 7. The shift times were reported as: 44.1% wonting from 8 A.M. to 4 P.M. and 33.9% working from 6. A.M. to 2. P.M. which is what they are doing now. 8. Regarding symptoms of fatigue: 1) Physical symptoms were: 48.3% complained of "feeling bean in the legs, ", and 39.3% complained of "general exhaustion. " 2) Psychological symptoms were: 37.6% said that "it is boring to talk"and 26.3% said" they had a desire to be alone". 3) Nitrogenic symptoms were 49.7% complained of "asthenopia"and 37.0% complained of"vertigo and "staggering legs". 9. When asked about the most fatiguing time during work, the following information was reported: 25.2% felt the first hour in the morning was most fatiguing while 22.9% felt the sixth hour in the evening, and 22.8% eelt the fifth hour at night was. 10. 38.4% complained of sleepiness at 3 A.M. and 35.0% at 4 A.M. during night work. 11. 38.1% found Sunday the most fatiguing work day and 20.% found Monday. 12. The results of the effects of their work on certain diseases: 51.1% showed those with anemia as most effected by work. 13. In their Response to the question, "do you eat breakfast\ulcorner"57.0%, the largest portion, answered, " none at all ": 36.3%, enough. 14. Regarding the accident rate relating to the length of time employed at the company 28.5% was the highest accident rate from 5year to 6 year. As a result of this study, it could be concluded that the employer should consider the following points: 1. employ according to the worker′s vocational aptitude. 2. adjust the shifts. 3. offer rest time and off days, and establish recreational facilities. In the end we can contribute to the promotion of the workers of the workers and to the prevention of accidents due to industrial fatigue.

• Journal of Ocean Engineering and Technology
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• v.32 no.3
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• pp.151-157
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• 2018

Offshore structures are exposed to low- and high-frequency responses due to environmental loads, and fatigue damage models are used to calculate the fatigue damage from these. In this study, we tried to optimize the main parameters used in fatigue damage calculation to derive a new fatigue damage model. A total of 162 bi-modal spectra using the elliptic equation were defined to describe the response of offshore structures. To calculate the fatigue damage from the spectra, time series were generated from the spectra using the inverse Fourier transform, and the rain-flow counting method was applied. The considered optimization variables were the size of the frequency increments, ratio of the time increment, and number of repetitions of the time series. In order to obtain optimized values, the fatigue damage was calculated using the parameter values proposed in previous work, and the fatigue damage was calculated by increasing or decreasing the proposed values. The results were compared, and the error rate was checked. Based on the test results, new values were found for the size of the frequency increment and number of time series iterations. As a validation, the fatigue damage of an actual tension spectrum found using the new proposed values and fatigue damage found using the previously proposed method were compared. In conclusion, we propose a new optimized calculation process that is faster and more accurate than the existed method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.8
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• pp.751-757
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• 2016

The aim of this study is to estimate the reliability of fatigue limit of the material used for crank throw components according to the staircase method. The material used for crank throw components is forged S34MnV grade steel, which is heat treated by normalizing and tempering. In this work, to predict the reliability of the design fatigue strength, axially loaded constant amplitude fatigue testing was conducted. The test specimens were loaded with an axial push/pull load with a mean stress of 0 MPa, which corresponds to a stress ratio of R=-1. The fatigue test results were evaluated by Dixon-Mood formulas. The values of mean fatigue strength and standard deviation predicted by the staircase method were 296.3 MPa and 10.6 MPa, respectively. Finally, the reliability of the fatigue limit in some selected probability of failure is predicted. The proposed method can be applied for the determination of fatigue strength for design optimization of the forged steel.

• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.251-257
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• 2017

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner's Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

• Korean Journal of Occupational Health Nursing
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• v.8 no.2
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• pp.162-168
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• 1999

To investigate industrial fatigue and low back pain, the questionaire survey for subjective symptoms of fatigue and low back pain was carried out 305 nurses in general hospital in Korea. Nurses participated to this study were divided into low back pain group(LBP) and control group, according to the self-reports by written questionaires. The subjective sysptoms of fatigue comprised three groups of 10 items each, representing dullness and sleepiness(level of cerebral activation), difficulty in concentration(level of motivation) and bodily projection of fatigue. The resultant data were processed for $x^2$-test, t-test to confirm the associations. The results were as follows: 1. 28 items of fatigue subjective symptoms exept two item, 'feel thirsty and 'feel ill', were directly associated with low back pain. 2. The percentage of fatigue complaint were significantly higher in LBP group than control. 3. Of the 30 items of fatigue subjective symptoms, the highest percentage was accounted for 'legs feel heavy', 'eye strain', 'feel stiffness in the neck or the shoulders' followed by 'feel like lying', 'whole body feels tired', 'feel a pain in the low back', 'feel drowsy' and in the order of sequence. 4. The average weighted score for the first group of fatigue items(dullness and sleepiness) was the largest among three groups and was followed by the second group(difficulty in concentration) and the third group (bodily projection of fatigue) in the order of sequence, suggesting the heavier mental and shift work stress of the female workers.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.441-449
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• 2016

Agricultural tractors are designed using the empirical method due to the difficulty of measuring precise load cycles under various working conditions and soil types. Especially, directly drives various tractor implements, the power take off (PTO) gear. Therefore, alternative design methods using gear design software are needed for the optimal design of tractors. The objective of this study is to simulate fatigue life of the PTO gear according to the operating point of the tractor engine. The PTO gear was made with SCr415 alloy steel with carburizing and quenching treatments. The fatigue life of the PTO gear was simulated by using bending and contact stress according to the torque of the load levels. The PTO gear simulation was conducted by the KISSsoft commercial software for gear analysis. Bending and contact stress were calculated by the ISO 6336:2006 Method A and B. The simulation of fatigue life was calculated by the Miner's cumulative damage law. The total fatigue life of tractors can be estimated to 3,420 hours; thus, 3,420 hours of fatigue life were used in the simulation of the PTO gear of tractors. The main simulation results showed that the maximum fatigue life of the PTO gear was infinite fatigue life at maximum engine power. Minimum fatigue life of the PTO gear was 19.61 hours at 70% of the maximum engine power. Fatigue life of the PTO gear changed according to load of tractor. Therefore, tractor work data is needed for optimal design of the PTO gear.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7126-7137
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• 2015

This study explored the quality of nursing services in relation to a nurse's psychosocial factors (type A behavior pattern, self-esteem, locus of control, and anxiety), job stress, and fatigue. This study targeted 503 nurses who currently work at six different general hospitals in Daejeon city, The data was collected by self-administered questionnaire which was surveyed from April 1 to June 30, 2014. As the result of analysis of covariance, psychosocial factors affect the quality of nursing services more than job stress or fatigue. In addition to that, as parts of psychosocial factors, high self-esteem and low fatigue, job stress, and anxiety increase the quality of nursing services. The research above implies that the quality of nursing services of nurses who work at the general hospital has a correlation with not only the psychosocial factors but also job stress, and fatigue.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.39-49
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• 1998

In this work, fatigue tests by axial loading were carried out to investigate the effect of stress ratio on the growth behaviors of surface fatigue crack for SM45C steel and Al 2024-T4 alloy. The growth behaviors of surface crack have been monitored during fatigue process by measuring system attached CCTV and monitor. When the growth rates of surface crack were investigate by the concept of LEFM based on Newman-Raju's .DELTA.K, the dependence of stress ratio appears both SM45C steel and Al 2024-T4 alloy. Therefore, modified stress intensity factor range, .DELTA.K' [=(1+R)/sup n/.DELTA.K] are intorduced to eliminate the dependence of stress ratio. Using .DELTA.K', it is found that the dependence of stress ratio disappears both SM45C steel and Al 2024-T4 alloy.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.1
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• pp.53-64
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• 1987

Low Cycle fatigue data through stress controlled and strain controlled tests at room temperature were obtained for solution treated and thermally aged 304 stainless steel. All the tests were conducted with the greguency, 1Hz of stress controlled and the strain rate, 40%/min of strain controlled. The aged specimen had the longer fatigue life at the lower stresses than at the higher stresses. It is shown that the fatigue limit of the aged specimen was a little higher than that of the solution treated specimen. It is considered to be due to the presence of carbide precipitates at grain boundary which depressed the crack propagation. The aged specimen showed the larger alternating stress and the more rapid cyclic work harding than the solution treated specimen. Bauschinger effect of the aged specimen was not pronounced than that of the solution treated specimen.