• Structural Engineering and Mechanics
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• 제55권4호
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• pp.885-900
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• 2015

This paper introduces Romberg-Richardson's method as one of the numerical integration tools for computation of stress intensity factor in a pre-cracked specimen subjected to a complex stress field across the crack faces. Also, the computation of stress intensity factor for various stress fields using existing three methods: average stress over interval method, piecewise linear stress method, piecewise quadratic method are modified by using Richardson extrapolation method. The direct integration method is used as reference for constant and linear stress distribution across the crack faces while Gauss-Chebyshev method is used as reference for nonlinear distribution of stress across the crack faces in order to obtain the stress intensity factor. It is found that modified methods (average stress over intervals-Richardson method, piecewise linear stress-Richardson method, piecewise quadratic-Richardson method) yield more accurate results after a few numbers of iterations than those obtained using these methods in their original form. Romberg-Richardson's method is proven to be more efficient and accurate than Gauss-Chebyshev method for complex stress field.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.73-78
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• 2004

In this research, the photoelastic experimental hybrid method with Hook-Jeeves numerical method has been developed: This method is more precise and stable than the photoelastic experimental hybrid method with Newton-Rapson numerical method with Gaussian elimination method. Using the photoelastic experimental hybrid method with Hook-Jeeves numerical method, we can separate stress components from isochromatics only and stress intensity factors and stress concentration factors can be determined. The photoelastic experimental hybrid method with Hook-Jeeves had better be used in the full field experiment than the photoelastic experimental hybrid method with Newton-Rapson with Gaussian elimination method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.150-154
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• 2008

In this research, stress components and principal stresses of O-ring under internal pressure and under uniform squeeze rate were obtained from the stress freezing method of photoelastic experiment and photoelastic experimental Hybrid method for 3-dimensional problems. The obtaining processes of those were introduced. It was certified that the processes of those are effective for the 3-dimensional stress analysis of structures. Stress freezing method, the obtaining processes of those and photoelastic experimental hybrid method were effectively applied to the stress analysis of O-ring made from rubber that under uniform deformation and internal pressure. Stress components and principal stress of Oring under uniform squeeze rate and under internal pressure were analyzed.

• 대한기계학회논문집
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• 제16권10호
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• pp.1890-1899
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• 1992

본 연구에서는 이종재료간의 Ⅴ-노치균열의 노치각도 및 재료의 종류에 따른 응력특이성지수와 응력강도 계수 해석에 각각 뉴톤-랍슨법(newtonraphson method), 뉴톤-랍슨법과 최소자승법을 이용한 선점법(collocation method)인 수치해석적 방법을 응용하고, 광탄성 등색선 무늬를 컴퓨터 그래픽하여 응력특이성지수와 응력강도계수가 모우드(mode)에 미치는 특성과 경계요소법(boundary element method)으로 응력해석한 결과로써 선점법을 이용하여 응력강도계수를 해석하고 기존의 결과등과 비교, 검토하 고자 한다.

• Journal of Welding and Joining
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• 제21권6호
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• pp.71-76
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• 2003

For the purpose of clarifying the influence of welding residual stress to the fatigue crack propagations behaviour, an analytical investigation based on finite element method is performed to examine the opening behaviour of tip-closed crack in the compressive residual stress. A finite element model comprised of contact elements for the crack plane and plane stress elements for the base material is used to evaluate crack opening stress of the crack existing in the residual stress field. Also an analytical method based on the superposition principle to estimate the length of opened part of tip closed crack and the stress distribution adjacent to the crack during uploading is applied to the finite element model. The software for the analysis is ABAQUS, which is a general purpose finite element package. The results show that stresses distributed on the crack surfaces are reduced and approached to zero as the applied stresses are increased up to crack tip opening stress and no mechanical discontinuity is found at the boundary of contact elements and plane stress elements. It is verified that the opening behavior of the fatigue crack in the residual stress can be predicted by finite element method with the proposed analytical method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.90-95
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• 2004

In this study, we proposed new method to mitigate tensile welding residual stress for preventing PWSCC in CRDM nozzle. Residual stress analysis using finite element method is performed to confirm benefit of the new method. In case of applying existing method, tensile axial residual stress decrease by about 28% and tensile hoop residual stress decrease by about 33%. In case of applying the new method, tensile axial residual stress decrease by about 32% and tensile hoop residual stress decrease by about 43%. Therefore, we conclude the new proposed method is more effective to prevent PWSCC than existing method.

• Journal of Welding and Joining
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• 제21권7호
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• pp.71-77
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• 2003

In this study, an investigation based on the superposition principle to predict residual stress redistribution caused by crack propagation itself initially through residual tensile stress field was performed by finite element method. The tendency in residual stress redistribution caused by crack propagation recognized both from the analytical results and experimental result was the residual stress concentration consecutively occurred in the vicinity of crack tip even the situation that the crack propagated to the region initially residual compressive stress existed. The software for the analysis is ABAQUS, which is a general purpose finite element package. The analytical method that attempt to take the plastic deformation at the crack tip due to tensile residual stress into the consideration of residual stress redistribution caused by crack propagation was proposed. The plastic zone size at the tip of fatigue crack and redistributed residual stresses were calculated by finite element method on the bases of the concept of Dugdale model. Comparing these analytical results with experimental results, it is verified that the residual stress redistribution caused by crack propagation can be predicted by finite element method with the proposed analytical method.

• 한국학교ㆍ지역보건교육학회지
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• 제23권4호
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• pp.1-15
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• 2022

Objectives: The purpose of this study was to examine the mediating effect of Stress coping method in the relationship between Covid-19 stress and academic burnout of university students in the long-lasting Covid-19 situation. Methods: The subjects of this study were 323 college students and data were collected by on-line questionnaire survey. The collected data was analyzed using SPSS 23.0 and t-test, ANOVA, multiple linear regression analysis were conducted. Also mediation analysis was performed according to the Baron & Kenny method. Results: The results were as follows. First, students with high Covid-19 stress had high academic burnout by regression analysis. Second, in the stress coping method, the active coping method lowered academic burnout, and the passive coping method increased academic burnout. Third, the active coping method showed a partial mediating effect in the relationship between Covid-19 stress and the academic burnout(p<.01). Conclusions: In order to help college students cope with academic burnout caused by Covid-19 stress, it is recommended to guide students to use active coping method through counseling and education. Ultimately, it is necessary to support students to use various coping methods according to their situation appropriately.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.82-84
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• 2005

Fatigue assessment of welded structure is very sensitive to the method of local stress determination. Normally, hot spot stress which is surface stress extracted from 0.5t, 1.5t away from weld toe is widely used to obtain local stress. However, this method has a lot of limitation in the evaluation of fatigue strength. Therefore, mesh has to comply with strict requirements since stress extracted from this method strongly rely on mesh size and element types. And that method does not cover the stress gradient through thickness direction since only surface stress is considered. Recently, new method to obtain local stress is proposed, which is structural stress. This method has an advantage, which is mesh intransitiveness and covering the effect of both bending and axial stress in local area. In this paper, fatigue test data for various welded joints was analyzed to review the reliability of structural stress. As a result, it is verified that S-N curve using structural stress guaranteed single master curve for various joint type and testing condition.

• 한국병원경영학회지
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• 제15권3호
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• pp.17-32
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• 2010

The purpose of this study is to analyze the influence of DISC behavior pattern, stress-managing method, and the stress level on job attitude of hospital Employees, and to provide suggestions for effective human resources management in hospital settings. First, the research suggested emotional or aversive stress-managing method had significant influence to the stress level, whereas DISC behavior patterns did not. Second, to the job satisfaction, Influence, Compliance and Steadiness of DISC behavior patterns, challenging or aversive stress-managing method, and the stress level showed immediate meaningful effect. Third, for the system immersion, challenging or emotional ress-managing method as well as the job satisfaction showed direct influence. Especially, the challenging method had not only a direct but an indirect effect through mediating job satisfaction.