• 한국응급구조학회지
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• 제12권3호
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• pp.71-86
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• 2008

Purpose : This study was to examine the influence of job stress of 119 Emergency Medical Technician on fatigue and job satisfaction. Methods : Subjects of this study were 228 Emergency Medical Technicians who worked at 119 Safety Center of total 92 fire stations in 12 cities of Gyeonggido including U, N, H, B, A, S, Y, G, G, G, P and I and the period of data collection was from July 11 to Sep. 10, 2007. Collected data were analyzed with SPSS 14.0 version. Results : Conclusions of this study were as follows. 1) Factor related to organization among job stress factors had the greatest influence on fatigue (B = 0.334, p < 0.01), followed by crisis situation factor (B = 0.2042, p < 0.01), inappropriate treatment factor (B = 0.174, p < 0.05), role conflict factor as special job (B = 0.109, p < 0.05) and professional knowledge and technique factor (B = 0.109, p < 0.05), and the influence of job stress factors on fatigue was explained as $R^2=0.340$. 2) Mental burden factor of job stress factors had the greatest influence on job satisfaction (B = -0.606, p < 0.01), followed by organization factor (B = -0.473, p < 0.01) and interpersonal relation and conflict factor (B = -0.339, p < 0.01), and the influence of job stress factor on fatigue was explained as $R^2=0.308$. Conclusions : Job stress of 119 rescuer is increasing continuously and such an accumulated stress lowers the job efficiency. In order to reduce, job stress, it is important to extend(${\rightarrow}$ have) proper self-development, maintain close relationships and mutual correlations among members of organization in personal dimension and to solve the role conflicts, define the organizational roles and simplify excessive job description into concrete work.

• 한국응급구조학회지
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• 제12권2호
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• pp.85-97
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• 2008

Purpose : This study was cross-sectional study to examine the influence of job stress in 119 briefing room workers and aimed to provide the important basic materials for improving working conditions of 119 briefing room workers and further studies. Methods : This study selected 271 workers of 119 briefing room at National Emergency Management Agency and fire stations, metropolitan cities and provinces to examine the influences of job stress of 119 briefing room workers on depression. and as a result of analysis, the following conclusions. Results : 1) The whole average of job stress measure was 3.30. The highest area was interpersonal relationship factor as 3.41, 'job characteristic factor' as 3.36 and communication factor' as 3.01. 2) Total score of whole items of depression was 11.88 and showed slight depression level. 3) There was static correlation between job stress and depression(r=44.7, p= .000). There were statistically significant static correlations between job stress factor and depression(r= .388, p= .000), interpersonal relationship factor and depression(r= .471, p= .000), and communication factor and depression(r= .386, p= .000). 4) There was statistically significant difference in the influence of job stress on depression(B=8.575, p< .001). Influence of job stress on depression was explained as $R^2=.200$. When job stress factors as independent variables were input, interpersonal relationship factor(B=5.062, p< .001) had the greatest influence on depression and there was no statistically significant difference in communication factor(B=2.490, p< .05). Conclusions : It is considered that development of the various programs including program for getting rid of job stress of 119 briefing room workers and counseling program will be needed. particularly, factors such as human relationships and communication in the area of job stress must be the first priority.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.280-285
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• 2001

As an integral part of the probabilistic fracture mechanics analysis, stress intensity factor calculation scheme for semi-elliptical surface flaws in thin-walled cylinder has been introduced. The approximation solution utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite element analysis for cooldown boundary condition. The analysis results confirmed that the simplified methods provided sufficiently accurate stress intensity factor values for axial semi-elliptcal flaws on the surface of the reactor pressure vessel.

• 대한기계학회논문집
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• 제18권12호
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• pp.3227-3235
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• 1994

This paper deals with an evaluation of the residual stress due to shot peening induced in a carburized gear tooth and its application to the fatigue crack propagation problem. A practical method is proposed on the basis of the assumption that the residual stress is caused by the difference of volume expansion in the case and the core, and the influence of both the reduction of retained austenite and the strain due to shot peening are considered. The evaluated residual stress is close to the measured stress, though the surface stress is rather overestimated. The stress intensity factor is computed by the influence function method, and it is shown that the factor is decreased by the residual stress in shot peened gear tooth. The shot peening is fairly effective to the reduction of fatigue crack growth rate. The crack propagation is simulated and the resistance due to shot peening is quantitatively demonstrated and discussed.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.319-328
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• 2006

A simple approximation method for the stress intensity factor at the tip of the axial semielliptical cracks on the cylindrical vessel is developed. The approximation methods, incorporated in VINTIN (Vessel INTegrity analysis-INner flaws), utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite element analysis for internal pressure, cooldown, and pressurized thermal shock loading conditions. For these, 3-D finite-element analyses are performed to obtain the stress intensity factors for various surface cracks with t/R=0.1. The approximation solutions are within $\pm2.5%$ of the those of finite element analysis using symmetric model of one-forth of a vessel under pressure loading, and 1-3% higher under pressurized thermal shock condition. The analysis results confirm that the approximation method provides sufficiently accurate stress intensity factor values for the axial semi-elliptical flaws on the surface of the reactor pressure vessel.

• Journal of Welding and Joining
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• 제7권1호
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• pp.28-35
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• 1989

The fatigue crack growth behavior in GTA butt welded joints of Al-Alloy 5052-H38 was examined using Single Edge Notched(SEN) specimens. It is well known that welding residual stress has marked influence on fatigue crack growth rate in welded structure. In the general area of fatigue crack growth in the presence of residual stress, it is noted that the correction of stress intensity factor (K) to account for residual stress is important for the determination of both stress intensity factor range(.DELTA.K) and stress ratio(R) during a loading cycle. The crack growth rate(da/dN) in welded joints were correlated with the effective stress intensity factor range(.DELTA.Keff) which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the welded joints were examined by using superposition of redistributed residual stress and discussed in comparison with the results of the initial welding residual stress superposition.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2390-2398
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• 2002

For integrity analysis of nuclear reactor pressure vessel, including the Pressurized thermal shock analysis, the fast and accurate calculation of the stress intensity factor at the crack tip is needed. For this, a simple approximation scheme is developed and the resulting stress intensity factors for axial semi-elliptical cracks in cylindrical vessel under various loading conditions are compared with those of the finite element method and other approximation methods, such as Raju-Newman's equation and ASME Sec. Xl approach. For these, three-dimensional finite-element analyses are performed to obtain the stress intensity factors for various surface cracks with t/R = 0.1. The approximation methods, incorporated in VINTIN (Vessel INTegrity analysis-INner flaws), utilizes the influence coefficients to calculate the stress intensity factor at the crack tip. This method has been compared with other solution methods including 3-D finite clement analysis for internal pressure, cooldown, and pressurized thermal shock loading conditions. The approximation solutions are within $\pm$2.5% of the those of FEA using symmetric model of one-forth of a vessel under pressure loading, and 1-3% higher under pressurized thermal shock condition. The analysis results confirm that the VINTIN method provides sufficiently accurate stress intensity factor values for axial semi-elliptical flaws on the surface of the reactor pressure vessel.

• 한국안전학회지
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• 제12권3호
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• pp.30-37
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• 1997

This paper deals with the residual stress of carburized spur gears is calculated being on the assumption that the main cause of residual stress is the volume difference between case and core due to the martensitic transformation in cooling. A formula is proposed to estimated the residual stress from the hardness and the amount of retained austenite. The estimated residual stress is close to the stress measured by X-ray method. The estimated residual stress is applied to the analysis of the fracture mechanics of carburized spur gear teeth. The stress intensity factor due to the residual stress is demonstrated. The stress intensity factor is computed by the influence function method, and it is shown that the factor is decreased by the residual stress in Carburized gear tooth.

• Journal of Welding and Joining
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• 제22권4호
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• pp.59-64
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• 2004

The purpose of this study is to investigate the influence of weld bead profiles on stress concentration factors of double V groove butt-welded joints. The influence of three parameters such as toe radii, flank angles and bead heights on the stress concentration factors is studied by finite element analysis. It is shown that the three parameters have similar effects on the stress concentration factors. Finally a formula to estimate the stress concentration factors considering the three parameters and others is proposed and estimated results are compared with the results obtained by finite element analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.539-542
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• 2000

In this paper, the influence of circular void on a crack in piezoelectric materials under mechanical and electric loads is investigated by using finite element method code, ANSYS. Both ceramics and piezoelectric materials are compared with stress intensity factor and crack extension force at crack tip on arbitrary located circular void under Mode I loads. It was found that piezoelectric materials's crack extension force is larger than ceramics.