• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.4
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• pp.873-882
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• 1990

본 연구에서는 작은 크랙이 중앙 크랙선단 주위에 대칭으로 배치 분포되어 있 는 유한 평판의 경우에 대한 것으로, 우선 균일분포하중을 받는 정방형판에 분포크랙 이 있는 경우 분포크랙의 위치에 따른 중앙 크랙 선단에서의 응력확대계수의 변화를 유한요소법으로 해석하여 등응력확대계수 곡선들로 나타냈다. 그리고 크랙들 사이의 상호 간섭에 의해 일어나는 소성영역도 고려하여 그 안정성을 검토하여 보았는데, 특 히 크랙들이 서로 가까와 지면 그 크랙들 간에 상호간섭이 커져 소성영격이 크랙선단 주위에 크게 발생되므로써 크랙들은 쉽게 연결되고 합체로 인한 크랙성장이 되어 파괴 됨을 예측할 수 있고 중앙 크랙선단 주위의 분포크랙의 위치에 따른 소성영역 변화도 유한요소법으로 해석하여 도식적으로 나타냈다.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.172-181
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• 2003

In this study, the stress intensity factor of center crack tip is calculated by the superposition method when it is surrounded by symmetrically distributed small cracks. The values of stress intensity factors of center crack tips are compared with those of the center crack tips calculated by the superposition method. These compared errors are influenced by the locations of distributed small cracks. These errors are inspected. When small cracks overlap and approach near the center crack tip, the effect of interaction caused by these cracks becomes noticeable and these errors become larger. In case of multiple distributed small cracks except this case, the stress intensity factor of the center crack tip is easily calculated by the superposition method.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.63-69
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• 2005

For the case that center crack is surrounded by four small cracks which are symmetrically distributed around center crack, the same values of normalized stress intensity factor of center crack according to the position of the tip of small cracks are located on the smooth curve. And the stress intensity factor according to any position of small cracks can be sufficiently obtained from this curve. The plastic zones between distributed cracks are also investigated by changing the positions of nearly small cracks. The occurrence of plastic zone due to the interaction between center crack and small cracks are analyzed by finite element method. The mechanical behavior at the vicinity of crack tips is investigated by plastic areas. The changes of plastic zones according to positions of distributed cracks are drawn schematically. The safety of materials is also analyzed.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.244-250
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• 1998

In this study, the stress intensity factors of center crack are analyzed when it is surrounded by symmetrically distributed small cracks. The values of stress intensity factors of the center crack are greatly influenced by the locations of distributed small cracks. When small cracks overlap or approach near the tip of a center crack, the effect of interaction arisen by these cracks becomes noticeable. In case of multiple distributed small cracks, the stress intensity factor of a center crack is found to be efficiently determined by the superposition method.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.591-594
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• 1998

Biodegradable microsphere containing bovine serum albumine (BSA) as a model drug were prepared with the microgel based on poly(caprolactone diol) by a modified solvent evaporation method. The influence of the stirring speed, the concentration of microgel and the mixing rate but increased with increasing the concentration of microgel in methylene chloride. The biodegradability of microsphere in 100 unit/mL of lipase solution was investigated. A lot of small pores appeared on the surface of microsphere after 3 hours of incubation time and the pores and cracks were developed with increasing the incubation time and microsphere lost their own shape after 36 hours of incubation time.