• International Journal of Precision Engineering and Manufacturing
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• v.3 no.3
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• pp.76-81
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• 2002

In order to study the fatigue crack and retardation mechanism in variable loading, the effects of crack tip branching in crack growth retardation were examined. The characteristics of crack tip branching behavior were considered with respect to microstructure and crack tip branching angle was examined. Crack tip branching was observed along the grain boundary of finite and pearlite structure. It was found that the branching angle ranges from 25 to 53 degrees. Using the finite element method, the variable of crack driving farce to branching angle was examined. The effective crack driving farce (K$\_$eff/) decreased as the branching angle increased. The rate of decrease was 33% for kinked type and 29% for forked one. It was confirmed that the effect of crack tip branching is a very important factor in crack growth retardation. Therefore, crack branching effect should be considered in building the hypothetical model to predict crack growth retardation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.856-860
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• 2002

The main objective of this study is to consider the effect of fatigue crack behavior on the variable depth of micro hole defects in SM20C at the symmetric position. The fatigue crack propagation test is performed by rotary bending fatigue test machine. The relationship between crack length(2a), cycles(N) and crack growth rate(da/dN) are investigated in this study. The result from the rotary bending fatigue test under the applied stress at 250MPa turned out that the fatigue life illustrated almost constant when the depth of symmetric micro hole deflects is both part A and B at the hope depth(h) = 0.5mm.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.61-68
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• 2002

From the viewpoint of linear fracture mechanics, the crack propagation behavior of two different structures having the same K-a relationship could be considered identical. In this study the stress distribution in an infinitely wide cracked plate with the same K-a relationship as in a real structure is defined as the equivalent stress distribution. Fatigue life of a real structural element can be predicted by applying the equivalent stress distribution to a simple structural element, and performing a fatigue crack propagation analysis. The K-a relationship for a structural member can be estimated by a finite element method or a simplified prediction method. The validity to obtain effective crack driving stresses by using the equivalent stress-distribution is examined.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.302-307
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• 2004

This paper reviewed characteristics of fatigue crack behavior observed by changing various shapes of initial crack and magnitudes of loading in compact tension shear(CTS) specimen subjected to shear loading. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Meanwhile, the secondary fatigue crack in the low-loading condition which was created in the notch root due to friction on the pre-crack face grew to a main crack. Influenced by the mode II loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. Propagation path of fatigue crack under the shear loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

• 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.

• Science of Emotion and Sensibility
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• v.17 no.4
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• pp.3-18
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• 2014

In this study, drivers' longitudinal car control, subjective fatigue, and perceived fidelity were compared between 2D and 3D display driving simulation. The results can be summarized as followings. First, in all target speed conditions, the drivers tended to drove faster in 2D display condition than 3D display condition. Second, speed deviation from target speed increased as target speed decreased. Third, distances between the lead vehicle and the driver's vehicle were significantly reduced in the 3D display condition when the speeds of the lead vehicle were relatively fast(i. e., over 80km/h). Fourth, although the perceived fidelity was not significantly different between the two display conditions, subjective fatigue was higher in the 3D display condition than in the 2D display condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.6
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• pp.859-864
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• 2022

Drowsy driving, one of the biggest causes of traffic accidents every year, is accompanied by various factors. As a general method to check whether or not there is drowsiness, a method of identifying a driver's expression and driving pattern, and a method of analyzing bio-signals are being studied. This paper proposes a driver fatigue detection system using deep learning technology and bio-signal measurement technology. As the first step in the proposed method, deep learning is used to detect the driver's eye shape, yawning presence, and body movement to detect drowsiness. In the second stage, it was designed to increase the accuracy of the system by identifying the driver's fatigue state using the pulse wave signal and body temperature. As a result of the experiment, it was possible to reliably determine the driver's drowsiness and fatigue in real-time images.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.141-149
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• 2012

This paper attempts to evaluate driving stability by the vibration of human body. The purpose of this research is to establish an evaluation methodology for controling the quality of road surface. The study was conducted to investigate the relationship between road surface profiles (IRI, International Roughness Index) and the fatigue caused by the vibration of human body. Furthermore, 3-axis acceleration in driving vehicles was examined based on sampling sections under various road conditions. The acceleration value of frequency bands were analyzed by the characteristics of road surface, and realized the range of human influence by conditions and type of road surface with ISO-2631 standards. In general, more human fatigue by vehicle vibration was appeared in concrete pavements with high IRIs based on the analysis from given test data. Whereas, The SMA asphalt pavement and the diamond grinded concrete pavement reduce the human fatigue.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1434-1440
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• 2011

In this paper, we assessed muscular activities of lower limbs and foot pressure for car and bus drivers according to operating three electronic pedals that we developed. To analyze drivers' physical exhaustion, muscular fatigue of lower limbs was evaluated. Eleven car drivers and six urban bus drivers were participated in this experiment. The virtual driving system was used for the real driving environment. The virtual driving system was comprised of a spring seat, a steering wheel, pedals (clutch, excel and brake pedals), a manual transmission and a virtual driving simulation. For the real vibration like situation on the road, six degree of freedom motion base system was used. Measured muscles were rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA) and gastrocnemius (Gn) muscles. For the quantitative muscular activities, integrated electromyography (IEMG) was analyzed. Muscular fatigues also were analyzed through the analysis of the median frequency. In addition, foot pressures were analyzed and compared through the peak and averaged pressure during the operating three developed electronic pedals. The experiments are conducted with total 17 drivers, 11 general public and 6 drivers. As a result of the analysis, electromyogram and fatigue analysis through intermediate frequency reduction for pedal-1 more efficient than other pedals. And foot pressure also was decreased. Consequently, we suggested the most efficient pedal and method to minimize the amount of cumulative fatigue.

• Journal of the Korean Home Economics Association
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• v.32 no.3
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• pp.197-206
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• 1994

The effect of dietary factors on the self-reported symptoms of fatigue were surveyed by the interviewing method among 119 taxi drivers in Cheonan area. It was shown that 86.5% of them were working over 11 hours a day and 34.4% of them over 16 hours. the level of job satisfaction was very low. Many of them felt fatigue during driving. Some symptoms of fatigue which many taxi drives said to be suffered from were headache physical exhaustion nervousness tired and sore eyes and anorexia. When related variables to the self-reported symptoms of fatigue were analyzed daily sleeping hours and exercise were significantly correlated with physical mental and neuro-motor fatigue, Subjects who had meals irregularly were greater than those who had regularly. In addition they tended to eat faster during working and 28.6% of them seldom had breakfast. Subjects who had meals irregularly consumed significantly less fat iron calcium vitamin A, and riboflavin. A and riboflavin and niacin than those who skipped it.