• 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.

• 한국직업건강간호학회지
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• 제21권1호
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• pp.27-36
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• 2012

Purpose: The purpose of this study was to identify the trends of nurses' stress based on the last 10 years of international research and to suggest directions for future research. Methods: Fifty three articles between 2002 and 2011 were selected using key words such as 'nurse' and 'stress' from the PubMed and CINAHL. Results: The number of experimental studies increased. The nurses from the various fields were studied. Most studies used a reliable and valid tool for measuring stress of specific nursing staff. The Internet survey was recently used for a data collection method. Significant variables correlated with nurses' stress were categorized into 8 domains: Individual susceptibility, quantitative workload, qualitative workload, physical environment, organizational factors, and interpersonal conflict. Conclusion: In Korea, the next phase of research on nurses' stress needs to consider the experimental study design to find more specific causal relationships. Also, it is necessary to develop the nurses' stress tool for reliable and valid measurement.

• 한국레이저가공학회지
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• 제5권3호
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• pp.1-8
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• 2002

Finite element analysis and experiment were peformed to estimate the fatigue strength for the lap joint of laser weld. To consider quantitatively residual stress which effects on the fatigue strength of the lap joint of laser weld, after three dimensional modeling for the longitudinal and transverse direction, residual stress fields in the weldment were calculated using thermo-elastic-plastic finite element analysis, then the equivalent fatigue stress considering the residual stress was obtained. To ensure reliability of calculated fatigue strength, fatigue tests were performed. The calculated and experimental results showed a good agreement. The fatigue strength considering a residual stress was lower than that of without considering a residual stress in the lap joint of laser welding. The fatigue strength in the transverse direction was higher than that of longitudinal direction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.157-162
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• 2003

Singular stress fields around three-dimensional wedges are examined, and the near-tip intensity is calculated via the two-state M-integral with the aid of the domain integral representation. A numerical example demonstrates the effectiveness and accuracy of the present scheme for computing the stress intensities of singular stresses near the generic three-dimensional wedges.

• 한국토양비료학회지
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• 제44권5호
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• pp.702-708
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• 2011

경사지 논토양에서 밭작물 재배확대를 위한 합리적인 배수개선 방법을 개발하기 위하여 "배수불량"인 경사지 논토양 (경사 7-15%, 지산통)을 대상으로 배수조건에 따라 "매우불량"인 논 2개 필지, "약간불량"인 논 2개 필지의 논둑 아래 기저부에 1열로 명거 (겉도랑 배수), 비닐차단막, 암거 (속도랑 배수), 관다발 등 네 가지 종류의 배수시설을 설치하여 배수개선 방법에 따른 콩의 수분 스트레스 반응 해석을 통한 배수개선 효과를 비교 분석한 결과 다음과 같은 결론을 얻었다. 배수시설 설치 후 콩 생육기간 중 지표 하 30 cm를 초과한 일평균 지하수위의 합계 ($SED_{30}$)는 명거배수가 147일로 높게 나타난 반면 암거배수가 31일로 나타났다. 또한 지하수위 30 cm를 초과한 수위의 합 ($SED_{30}$)은 명거배수 처리구가 2,207 mm, 비닐차단막 1,938 mm, 관다발 1,262 mm로 밭작물의 수분 스트레스 지표인 1,000 mm 보다 초과하였으나 암거배수 처리구에서는 444 mm 한계 스트레스 지표보다 낮은 경향을 보였다. 배수방법별 콩의 생육기간 중 수분 스트레스 지표 (SDI)는 명거배수 처리구 355.40, 비닐차단막 271.55, 관다발 171.55로 높은 경향을 보여 과습에 의한 영향을 가장 많이 받은 것으로 나타났으나, 암거배수 처리구에서는 64.75로 배수개선 효과가 가장 높은 것으로 나타났다. 배수개선에 따른 콩 수량은 배수 약간불량지가 배수 매우불량지에 비해 높았으며, 배수 약간불량지에 비해 매우불량지에서 배수방법별 수량변화의 차이가 크게 나타났다. 또한 명거배수 처리구 $1,585kg\;ha^{-1}$에 비해 암거배수 $2,086kg\;ha^{-1}$로 32%, 비닐차단막 $1,633kg\;ha^{-1}$로 3%, 관다발 처리구 $1,922kg\;ha^{-1}$로 21% 증수되었으며, 암거배수처리구가 다른 배수방법에 비해 통계적 유의성이 인정되었다. 따라서 "배수불량"인 경사지 논에서는 논둑 밑 1열의 암거배수시설을 설치로 논에서 밭작물의 안정적인 생산과 농지자원의 이용전환 즉 논을 밭으로 이용해야 하는 범용농지 기반조성에 조성을 위한 저비용의 실용적인 배수개선방법개발에 기여할 것으로 본다.

• 한국생산제조학회지
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• 제9권5호
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• pp.47-57
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• 2000

In this study, a fundamental approach to make clear the mechanism of the mutual interference and coalescence of stress fields in the vicinity of two crack tips on the process of their slow growth, using boundary element method. Automatic generation of quadratic discontinuous elements along both of the crack boundaries which can be defined by an arbitrary piece-wise straight geometry. The direction of the crack-extension increment is predicted by the maximum principal stress criterion, corrected to account for the discreteness of the crack extension. Along the computed direction, the crack is extended one increment. Automatic incremental crack-extension analysis with no remeshing, computation of the stress intensity factors by J-integral. Numerical stress intensity factors for two growing cracks in plane-homogeneous regions were determined.

• 한국생활과학회지
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• 제12권4호
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• pp.403-416
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• 2003

The recent study was examined the effects of stress related to self-esteem upon the types of deficiency, the genders, the grades. A Questionnaire was distributed to 172 elementary school students in 4th, 5th and 6th grades. The results of this study were as follows : First, children's stresses were related to their self-esteem and their self-esteem was explained mostly by the stress from home environment. Second, children's stress upon the birth order was higher in the first than in the second and the third birth order. Third, their self-esteem was explained mostly by the support from friends, teachers, and academic fields. Forth, children's stress of divorced and separated families as a reason of deficiency was higher than their stress upon the separation by death.

• 소성∙가공
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• 제16권6호
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• pp.463-466
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• 2007

Micro-wire made from straightening process invents high added value and it has been adopted many industrial fields. Therefore, many research activities about straightening process are advanced actively. It is known that fine straightness of micro-wire can be obtained by removing residual stress induced during the manufacturing processes. Generally, residual stress is removed or minimized through several drawing processes with heat treatment. In this study, the residual stress at each straightening process is calculated and monitored by finite element analyses and the main reason of stress change is investigated.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.15-22
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• 2008

Applications of bonded dissimilar materials such as integrated circuit(IC) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in bonded joints of dissimilar materials. In order to investigate the IC package crack propagating from the edge of die pad and resin, the fracture parameters of bonded dissimilar materials and material properties are obtained. In this paper, the thermal stress and its singularity index for the IC package were analyzed using 2-dimensional elastic boundary element method(BEM). From these results, crack propagation direction and path by thermal stress in the IC package were numerically simulated with boundary element method.

• Structural Engineering and Mechanics
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• 제22권5호
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• pp.613-629
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• 2006

In this paper a recently developed scaled boundary finite element method (SBFEM) is applied to simulate stress concentration for two-dimensional structures. In addition, a simple and independent formulation for evaluating the coefficients, not only of the singular term but also higher order non-singular terms, of the stress fields near crack-tip is presented. The formulation is formed by comparing the displacement along the radial points ahead of the crack-tip with that of standard Williams' eigenfunction solution for the crack-tip. The validity of the formulation is examined by numerical examples with different geometries for a range of crack sizes. The results show good agreement with available solutions in literatures. Based on the results of the study, it is conformed that the proposed numerical method can be applied to simulate stress concentrations in both cracked and uncracked structure components more easily with relatively coarse and simple model than other computational methods.