• Proceedings of the KSR Conference
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• 2007.05a
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• pp.340-350
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• 2007

The major objective of this study is to investigate the fatigue effects of rail pad on High Speed Railway with concrete slab track system. It analyzed the mechanical behaviors of HSR concrete slab track with applying rail pad stiffness based on fatigue effect(hardening and increasing stiffness) on the 3-dimensional FE analysis and laboratory test for static & dynamic characteristics. As a result, the hardening of rail pad due to fatigue loading condition are negative effect for the static & dynamic response of concrete slab track which is before act on fatigue effect. The analytical and experimental study are carried out to investigate rail pad on fatigue effected increase vertical acceleration and stress and decrease suitable deflection on slab track. And rail pad based on fatigue effect induced dynamic maximum stresses, the increase of damage of slab track is predicted by adopting fatigue effected rail pad. after due consideration The servicing HSR concrete slab track with resilient track system has need of the reasonable determination after due consideration fatigue effect of rail pad stiffness which could be reducing the effect of static and dynamic behavior that degradation phenomenon of structure by an unusual response characteristic and a drop durability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3149-3158
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• 1994

In this paper, using the formulation of dynamic equivalent load considering the effects of moment load and the equation to estimate the cage rotational speed, the new life equation of deep groove ball bearing under radial and moment loads was proposed. Fatigue life test apparatus with the measuring equipment of shaft and cage speed was designed and developed to be capable of subjecting combined radial and moment load. Fatigue life tests were executed by sudden death test method and the reliability of fatigue lives was evaluated by Weibull distribution analysis. From the results of fatigue tests and analysis, the relationships between film parameters and life adjustment factors were acquired. And it was turned out that so as to estimate the effect of moment load on fatigue life, the life adjustment factor as well as the dynamic equivalent load must be taken into account.

• The Journal of Korean Physical Therapy
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• v.30 no.2
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• pp.63-66
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• 2018

Purpose: The purpose of the current study was to examine the effects of exercise-induced fatigue of the plantar flexor muscle in the dominant ankle on the plantar flexor strength and postural control function of the contra-lateral side. Methods: Twenty-one young adults (male: 10, female: 11) volunteered to participate in this study. An exercise-induced fatigue protocol to induce fatigue was performed in the plantar flexor of the dominant ankle. For the fatigue protocol, the participants were instructed to raise their heels as high as possible in the position with one leg stance of the dominant lower limb, and the heel was then downed after holding for 1 second. The muscle strength of the contra-lateral plantar flexor was measured using a digital muscle strength test device, and the static and dynamic postural control were tested by acquiring the center of gravity velocity while performing one leg standing. A paired t-test was used to identify the differences between the pre- and post, and the data were analyzed using SPSS 12.0 software. Results: Comparison of the pre- and post-test data revealed a significant difference in the plantar flexor strength and dynamic postural control after exercise-induced muscle fatigue in the dominant side. On the other hand, there was no significant difference in the static postural control. Conclusion: These findings have practical implications, suggesting that unilateral muscle fatigue affects the ankle muscle strength and postural ability of the contralateral side.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.32-37
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• 2003

Evaluation of fatigue strength on the spot welded part is very important for strength design of spot welded steel structures. In this paper, we could get the life cycle of the spot welded part using the lethargy coefficient obtained through the quasi-static tensile shear test for the specimen welded by current 10kA. The reliability evaluation of the life cycle is completed by comparing the life cycle calculated under the constant loading rate with the life cycle obtained by dynamic fatigue test. And then the result calculated by the lethargy coefficient is verified through the lift cycle calculated using the dynamic final tensile stress formula under the increased loading speed. This way can make save the time and cost in processing of predicting the life cycle of a structure.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.24-31
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• 1995

This paper shows the fatigue durability test method for vehicle suspension systems. Durability should be assured for the safe driving during vehicle life cycle. A computer simulation for the vehicle dynamics was used to obtain dynamic loads that were required for the fatigue durability test. Durability tests were done for an Important load-carrying component of the suspension system. Stress analyses using stresscoat and strain gages were also done for the component. This study demonstrated an effective method for the fatigue durability test.

• Steel and Composite Structures
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• v.46 no.6
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• pp.745-757
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• 2023

In order to study the fatigue performance of the flat steel plate-lightweight aggregate concrete hollow composite bridge slab subjected to fatigue load, both static test on two specimens and fatigue test on six specimens were conducted. The effects of the arrangement of the steel pipes, the amplitude of the fatigue load and the upper limit as well as lower limit of fatigue load on failure performance were investigated. Besides, for specimens in fatigue test, strains of the concrete, residual deflection, bending stiffness, residual bearing capacity and dynamic response were analyzed. Test results showed that the specimens failed in the fracture of the bottom flat steel plate regardless of the arrangement of the steel pipes. Moreover, the fatigue loading cycles of composite slab were mainly controlled by the amplitude of the fatigue load, but the influences of upper limit and lower limit of fatigue load on fatigue life was slight. The fatigue life of the composite bridge slabs can be determined by the fatigue strength of bottom flat steel plate, which can be calculated by the method of allowable stress amplitude in steel structure design code.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.850-856
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• 1998

The dynaamic fatigue behavior of alumina ceramics was observed at room temperature using four-point bending method. Dynamic fatigue fracture strength was observed as function of down speed and notch length. The crack growth exponent of the specimens was calculated from the fracture strength and lifetime in dynamic fatigue test. After loading the stresses in the range of 0% to 105% compared with the average in-ert strength the value of residual fracture strength was measured for unnotched and 0.5mm notched speci-mens at the 0.001 and 0.0005 mm/min down speed respectively. After the 95% stress of the average inert strength was applied repeatedly the value of rsidual fracture strength was measured for 0.5mm notched specimens at the 0.001 and 0.0005 mm/min down speed respectively. The material constant A was found to be almost the same and not to depend on the loading mode or the down speed for unnotched and notched specimen. The value of fracture strength with time calculated from the constants n and A was in good agreement with the measured value.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.7
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• pp.344-351
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• 2006

The fatigue of back muscle in the repetitive lifting motion was studied using multiple parameters(FFT_MDF, RMS, 2C, NT) in this study. Recent developments in the time-frequency analysis procedures to compute the IMDF(instantaneous median frequency) were utilized to overcome the nonstationarity of EMG signal using Cohen-Posch distribution. But the above method has a lot of computation time because of its complexity. So, in this study, FFT_MDF(median frequency estimation based on FFT) algorithm was used for median frequency estimation of back muscle EMG signal during muscle work in uniform velocity portion of lumbar movement. The analysis period of EMG signal was determined by using the run test and lumbar movement angle in dynamic task, such as lifting. Results showed that FFT_MDF algorithm is well suited for the estimation of back muscle fatigue from the view point of computation time. The negative slope of a regression line fitted to the median frequency values of back muscle EMG signal was taken as an indication of muscle fatigue. The slope of muscle fatigueness with FFT_MDF method shows the similarity of 77.8% comparing with CP_MDF(median frequency estimation based on Cohen Posch distribution) method.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.213-218
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• 2006

For an evaluation of fatigue strength, the dynamic stress test of bogie frame for new electrical multiple unit was practiced in the real route line. And this results are summaries for a decision whether this vehicle can be operated safely for more than 25 years according to the international standard of the evaluation and its procedure.

• Physical Therapy Korea
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• v.20 no.3
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• pp.36-44
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• 2013

This study aimed to investigate the influence of shoe heel height and muscle fatigue on static and dynamic balance in young women. Thirty women who were used to wearing high heels volunteered to participate in this study. The shoe heel heights were 0 cm and 7 cm. And ankle plantar flexor fatigue was experimentally induced. Static and dynamic balance were measured using the one leg standing test (OLST) and the star excursion balance test (SEBT) in anterior, posteromedial, and posterolateral directions, respectively. Values in the OLST (shoe heel height 0 cm, $28.83{\pm}3.24$ sec to $26.12{\pm}6.13$ sec; and 7 cm, $24.75{\pm}7.09$ sec to $16.86{\pm}9.32$ sec) and the SEBT in anterior (shoe heel height 0 cm, $71.02{\pm}4.57%$ to $69.50{\pm}3.66%$; and 7 cm, $64.17{\pm}3.53%$ to $59.61{\pm}4.06%$) and posteromedial (shoe heel height 0 cm, $92.01{\pm}5.61%$ to $90.38{\pm}7.10%$; and 7 cm, $83.09{\pm}7.29%$ to $76.83{\pm}9.28%$) directions were significantly reduced when fatigue-inducing exercise was performed (p<.05). Furthermore, within these parameters, there were significant interaction effects between shoe heel height and fatigue condition (p<.05). These findings suggest that shoe heel height and muscle fatigue contribute to some changes in static and dynamic balance in young women, probably leading to negative effects on physical function during a variety of activities of daily living.