• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.11a
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• pp.216-221
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• 1999

A mental task combined with noise background is an effective model of laboratory stress for study of psychophysiology of the autonomic nervous system (ANS). The intensity of the background noise significantly affects both a subjective evaluation of experienced stress level during test and the physiological responses associated with mental load in noisy environments. Providing tests of similar difficulties we manipulated the background noise intensity as a main factor influencing a psychophysiological outcome and the analyzed reactivity along withe the noise intensity dimension. The goal of this study was to identify the patterns of ANS responses and the relevant subjective stress scores during performance of word recognition tasks on the background of white noise (WN) of the different intensities (55, 70 and 85 dB). Subjects were 27 college students (19-24 years old). BIOPAC, Grass Neurodata System and AcqKnowlwdge 3.5 software were used to record ECG, PPG, SCL, skin temperature, and respiration. Experimental manipulations were effective in producing subjective and physiological responses usually associated with stress. The results suggested that the following potential autonomic mechanisms might be involved in the mediation of the observed physiological responses: A sympathetic activation with parasympathetic withdrawal during mild 55 and 70dB noise (featured by similar profiles) and simultaneous activation of sympathetic and parasympathetic systems during intense 85dB WN. The parasympathetic activation in this case might be a compensatory effect directed to prevent sympathetic domination and to maintain optimal arousal state for the successful performance on mental stress task. It should be mentioned that obtained results partially support Gellhorn's (1960; 1970) "tuning phenomenon" as a possible mechanism underlying stress response.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6440-6445
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• 2014

In steel structures, including ships and offshore structures, defects induced during construction or in use causes cracks and damages. Calculation of the stress intensity factor (SIF) K is one method for crack analysis by fracture mechanics approach. In this paper, an evaluation of K was carried out using the J integral. In particular, in this study, a CT specimen was used to calculate the J integral. In the evaluation, 859 nodes and 1618 elements were used for the J integral calculation of the CT specimen by the in-house FEM program. A comparison of the result with the ASTM formula showed that the results from the current research of the J integral was in the 99% coincidence interval. Overall, cracks in this study can be studied satisfactorily by the J integral from the above mesh size.

• Journal of the Korean Society of Safety
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• v.12 no.2
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• pp.17-21
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• 1997

The fatigue crack propagation rate has so far been measured by the effective stress intensity factor range Δ K/sub eff/. But no research has been done to study how much the crack opening ratio influences the expectation of the fatigue crack propagation. Therefore, this paper evaluates of the crack opening ratio on the fatigue crack propagation life by using the method of parameter sensitivity study. Summarizing the result ; ( 1 ) When the crack opening ratio U' is high, the effect of U' gets larger than any other except for the material factor m. But when U' is low, the effect is also diminished. Therefore, the selection of the lowest value possible is desirable in the evaluation of life. (2) When the value of the material factor m is high, the effect of crack opening ratio U' is increased, at the same time the effect of the other parameters also increased wholly. The effect of material factor m itself on life is high, but in case the material factor m is high, that the effect of each parameter on life get higher is unique. In designing, better attention to the material selection should be drawn. (3) In case the stress ratio R gets smaller, the effect of crack opening ratio U' is unchangeable. But the effect of R itself remarkably decreases, and the effect of material factor m somewhat decreases.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.53-58
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• 2002

This paper aims to synthesize the research on fatigue mechanisms of high strength aluminum alloys which are widely used in motorcars or airplanes to prevent accidents. To measure the data of crack opening ratio, the same materials and methods are used for evaluating the fatigue crack propagation rate as an effective stress intensity factor. But, many researchers have brought different results. An exact crack opening ratio was, therefore, proposed for getting a more accurate fatigue crack propagation rate.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.267-272
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• 2000

The modeling on uplift pressure on the foundation of a dam on which it was constructed, and on the interface between the dam and foundation is a critical aspect in the analysis of concrete gravity dams. The evaluation of stress intensity factor at the crack tip of concrete gravity dam due to uplift pressure effect by surface integral method is performed in this study. The effects of body force, overtopping pressure and water pressure on the crack-face are also considered in this study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.924-930
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• 1991

본 연구에서는 크립게이지와 스트레인게이지를 사용하여 정확한 크랙 열림점 의 값을 제시하고져 한다.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.1988-1997
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• 2005

This study is concerned with structural integrity evaluations for the interference-fit flywheels in reactor coolant pumps (RCPs) of nuclear power plants. Stresses in the flywheel due to the shrinkage loads and centrifugal loads at the RCP normal operation speed, design overspeed and joint-release speed are obtained using the finite element method (FEM), where release of the deformation-controlled stresses as a result of structural interactions during rotation is considered. Fracture mechanics evaluations for a series of cracks assumed to exist in the flywheel are conducted, considering ductile (fatigue) and non-ductile fracture, and stress intensity factors are obtained for the cracks using the finite element alternating method (FEAM). From analysis results, it is found that fatigue crack growth rates calculated are negligible for smaller cracks. Meanwhile, the material resistance to non-ductile fracture in terms of the critical stress intensity factor (K$_{IC}$) and the nil-ductility transition reference temperature (RT$_{NDT}$) are governing factors for larger cracks.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.19-29
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• 1993

The static tensile tests of GFRP, ID300, CFRID300 and CFRPEEK were made on the plain and notched specimens at room temperature. The results were discussed based on linear notch mechanics which was proposed by H.Nistani. The fracture of notched GFRP, ID300, CFRID300 and CFRPEEK specimens is controlled by the elastic maximum stress, $({\sigma}_max)$, and the notch root racius,$\rho$, alone, independently of the other geometrical conditions. The relation between fracture nominal stress,$({\sigma}_max)$, and stress concentration factor, $K_t$ and a part where $({\sigma}_c)$ is nearly constant independent of $K_t$. A similar phenomenon can be seen in the fatigue tests of notched specimes under rotating bending or push-pull. The almost constant $({\sigma}_c)$ values correspond to the nearly constant apparent stress intensity factor, $K_{1pc}$ values, obtained by assuming ,$\rho$=0. This can be attributed to the existence of the stable crack. Linear notch mechanics is very useful for analyzing the static tensile fracture behavior of notched GFRP, ID300, CFRPEEK specimens.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.13-18
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• 2009

In this study, an equivalent unit load methodology has been presented to simplify the fatigue analysis procedure. And fuselage structure fatigue life has been evaluated based on equivalent unit load. Finite element analysis has been carried out to analyze the stress intensity factor and geometrical correction factor that is needed for crack growth analysis. And strain energy density factor is used to predict the initial direction of crack propagation.

• Composites Research
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• v.19 no.4
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• pp.15-22
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• 2006

One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.