• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.488-493
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• 2011

Authors previously suggested the design sensitivity analysis based on transmissibility function and identified the sensitivity of measured point over the small modification of system dynamics. On the other hand, the acceleration data will not reveal the strain information at the same location and authors suggested energy isoclines that successfully predict the fatigue damage on the interesting location to overcome the drawback of acceleration over fatigue society. Both of methodologies, sensitivity analysis and fatigue damage prediction, commonly use the response acceleration response as main indicator. In this paper, authors investigate the advanced method of vibration fatigue prediction using design sensitivity analysis to enhance the accuracy of predicted accumulated fatigue. Uni-axial vibration testing is performed with finite element model of a simple notched specimen and the prediction of fatigue damage at notched location is conducted for accelerations at different measurement locations that show different sensitivity contribution, either.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.519-528
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• 1994

Degradation problem due to long term service in machine or structure is now one of important problems in whole industrial field. In this study, pressure vessel steel, Cr-Mo steel, which was used more than 60,000 hours, was surface-modified by laser beam radiation for the improvement of fatigue strength. To find out optimum radiation condition, hardness, residual stress measurement and fatigue tests were carried out with the specimen of different radiation conditions. Experimental results show that micro-hardness values on the surface of the radiated specimens were approximately 2.2 times higher than those of un-radiated ones. In the depth direction of the specimen, hardness on the surface showed maximum value and was decreased at the inside the specimen. Different hardness values are due to the energy density Q which was absorbed by the specimen. Fatigue tests show that fatigue life was improved by the compressive residual stress after laser beam radiation. However, some specimens with differednt conditions show the shorter fatigue life. It means that laser beam radiation with optimum parameter can improve thae fatigue strength.

• The Journal of Korean Physical Therapy
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• v.32 no.4
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• pp.198-202
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• 2020

Purpose: This study examined the effects of a paraffin treatment with exercise on the muscle strength and fatigue of the hand according to the use of smartphones. Methods: The measurement subjects were 30 healthy males in their 20s who were divided randomly into the control and paraffin treatment groups. A typing exercise using a smartphone was performed. The pinch grip force was measured to evaluate the muscle strength of the thumb, and muscle fatigue analysis using electromyography was performed to analyze muscle fatigue. Results: The functional changes to the arm and the fatigue of the hand through the use of a smartphone were examined to determine the effects of the paraffin treatment. The dominant hand-pinch grip force test did not show a significant difference, but the non-dominant hand-pinch grip force test showed a significant difference between the groups (p=0.030). In the dominant hand fatigue test, there was a significant difference between the groups (p=0.037). In the non-dominant hand, there was a significant difference between time (p=0.012) and the groups (p<0.001). Conclusion: The effects of paraffin intervention on the hand muscle strength and fatigue due to repeated use of the smartphone were confirmed. These results can be used as a basis for clinical use and can be a guide for the correct use of smartphones, which are essential in modern life.

• Journal of Korean Biological Nursing Science
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• v.24 no.3
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• pp.141-149
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• 2022

Purpose: This study aimed to investigate the effects of grit and body composition on fatigue and burnout in shift-working nurses. Methods: A descriptive cross-sectional design using self-report questionnaires was employed. Data were collected between February and April 2021 from 192 shift-working nurses in 22 units of C tertiary hospitals. Of the 192, 175 nurses returned their completed questionnaires (return rate: 91.1%). The participants objectively measured their body composition for three consecutive days using a home body composition measurement scale. Results: Nurses with higher consistency of interest were more likely to have lower chronic fatigue (B = -5.23, p= .013), lower emotional exhaustion (B = -2.75, p< .001), and decreased depersonalization (B = -1.08, p= .014). Perseverance of effort was not statistically significant for fatigue; however, it was statistically significant for higher personal accomplishment among the subdomains of burnout (B= 2.50, p< .001). Skeletal muscle mass and body mass index had no significant effect on fatigue and burnout. Conclusion: To reduce fatigue and burnout in shift-working nurses, comprehensive efforts at the organizational and individual levels should be implemented to increase their grit. Further research is needed to determine whether body composition affects fatigue and burnout in shift-working nurses.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.28-31
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• 2023

This study presents a comprehensive procedure for the low cycle fatigue test of ultrasonically welded (UW) coated conductor (CC) lap-joints. The entire process is examined in detail, from the robust fabrication of the UW REBCO CC joints to the reliability testing under a low number of repeated cycle fatigue conditions. A continuous I_c measurement system enables real-time monitoring of I_c variations throughout the fatigue tests. The study aims to provide a step-by-step procedure that involves joint fabrication, electromechanical property (EMP) tests under uniaxial tension for stress level determination, and subsequent low-cycle fatigue tests. The joints are fabricated using a hybrid method that combines UW with adding In-Sn soldering, achieving a flux-free hybrid welding approach (UW-HW flux-free). The selected conditions for the low cycle fatigue tests include a stress ratio of R=0.1 and a frequency of 0.02 Hz. The results reveal some insights into the fatigue behavior, irreversible changes, and cumulative damage in the CC joints.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.8 no.3
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• pp.302-313
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• 2001

Purpose: To identify characteristics of chronic fatigue, difference between the duration of fatigue and characteristics of chronic fatigue, and association between chronic fatigue and related factors in adults. Method: The subjects for this study were 180 adults who had experienced fatigue for over one month The measurement tools were the Revised Fatigue Scale by Chalder et al. (1993), the Visual Analogue Scale-energy developed by Lee et al. (1991), the BEPSI (Brief Encounter Psychosocial Instrument) by Frank & Zyzanski (1988), Zung's self rating depression scale (1965) and life style items including exercise sleep, drinking smoking and diet as developed by the researchers. Results : Those who complained of fatigue over six months experienced higher disturbances in their daily life compared to those who had suffered from fatigue less than six months. There were a significant correlation between severity of fatigue and depression (r=.46, p<.001), stress (r=.41, p<.001), and sleep (r=.20, p<.01) Statistically significant relationships were found between severity of fatigue and amount of exercise per week (F=3.79. p<.05) disturbed sleep (t=-2.66, p<.01), number of times awakened during the night (F=3.48, p<.05) types of drinking (F=2.65, p<.05), and diet regularity (F=5.83, p<.01). The construction of a multiple regression model revealed an adjusted $R^2$ of .27 with the depression score serving the major predictor variables for severity of fatigue. Men and people in the younger age group were more energetic than women and those in other age groups. Also married people experienced more fatigue than people who were single. divorced or separated. Conclusion: In nursing interventions for fatigue, medical personnel should consider sociodemographic characteristics of the clients, ways to reduce of stress and counter disturbances in daily life and develop strategies for a health promoting life style.

• Journal of the Ergonomics Society of Korea
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• v.32 no.2
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• pp.207-215
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• 2013

Objective: This study aimed to investigate important human factors that should be considered when developing ultra-high definition TVs by reviewing measurement methods and main characteristics of ultra-high definition displays. Background: Although much attention has been paid to high-definition displays, there have been few studies for systematically evaluating human factors. Method: In order to determine human factors to be considered in developing human-friendly displays, we reviewed subjective and objective measurement methods to figure out the current limitations and establish a guideline for developing human-centered ultra-high definition TVs. In doing so, pros and cons of both subjective and objective measurement methods for assessing humans factors were discussed and specific aspects of ultra-high definition displays were also investigated in the literature. Results: Hazardous effects such as visually-induced motion sickness, visual fatigue, and mental fatigue in the brain caused by undesirable TV viewing are induced by not only temporal decay of visual function but also cognitive load in processing sophisticated external information. There has been a growing evidence that individual differences in visual and cognitive ability to process external information can make contrary responses after exposing to the same viewing situation. A wide vision, ultra-high definition TVs provide, can has positive and negative influences on viewers depending on their individual characteristics. Conclusion: Integrated measurement methods capable of considering individual differences in human visual system are required to clearly determine potential effects of super-high vision displays with a wide view on humans. All of brainwaves, autonomic responses, eye functions, and psychological responses should be simultaneously examined and correlated. Application: The results obtained in this review are expected to be a guideline for determining optimized viewing factors of ultra-high definition displays and accelerating successful penetration of the next-generation displays into our daily life.

• Journal of the Korean Society of Safety
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• v.17 no.1
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• pp.18-24
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• 2002

This study verified the relationship between fracture mechanics parameters(${\Delta}K,\;K_{max}$) and X-ray parameters ($(\sigma}_r,;B$) for G365 steel at elevated temperature up to $300{\circ}C$. The fatigue crack propagation test were carried out and X-ray diffraction technique according to crack length direction was applied to fatigue fractured surface. The residual stress on the fracture surface was found to increase in low ${\Delta}K$ region, reach to a maximum value at a certain value of $K_{max}$ or ${\Delta}K$ and then decrease. Residual stress was independent on stress ratio by arrangement of ${\Delta}K$ and half value breadth was independent by the arrangement of $K_{max}$. The equation of ${\sigma}_r-{\Delta}K$ was established by the experimental data. Therefore, fracture mechanics parameters could be estimated by the measurement of X-ray parameters.

• 한국기계연구소 소보
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• s.15
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• pp.75-87
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• 1985

A review was performed on fatigue life prediction and strength evaluation of shot peened parts. Fatigue strength of machine parts can be improved by shot peening due to compressive residual stresses on such parts. Compressive residual stress cannot be uniquely define by peening intensity. Several measuring methods of residual stress and the principle of hole drilling method are presented. Exploratory measurement of residual stress was performed on the shot peened SM35C plate with the hole drilling method. Fatigue life and failure location of shot peened parts under bending load can be predicted by a damage parameter which is incorporated with material properties, residual stress, and applied stress conditions. Some method are presented to predict the fatigue strength of shot peened parts at any given life. Shot peening gives its full benefit to the notched machine parts of high strength steels.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1465-1473
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• 1994

This paper describes the development strategy and contents of a fatigue life evaluation system, FLEVA. The system is composed of 4 parts; material properties, load histories, cycle counting and life prediction. The cycle counting is based on the rain-flow counting method and peak counting method, and the life prediction is performed based on the linear damage rule. Material properties(static, fatigue) are also provided as a database obtained by a computer aided test system. Case study is performed to verify the developed program.