• 대한기계학회논문집
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• 제17권5호
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• pp.1172-1182
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• 1993

본 연구에서는 버형성중의 파단을 파단전의 소성변형의 과정이 파단에 영향을 미치는 연성파단(ductile fracture)으로 간주하여 McClintock의 연성파단에 관한 모델 을 이용하여 버형성중의 파단변형도를 얻었다. 이 파단변형도가 인장시험으로부터 얻 은 파단변형도와 커다란 오차가 없음을 확인하여 편의상 인장시험에서의 파단변형도를 버형성중의 파단발생 판정기준으로 사용하였다. 버형성이 시작된 이후에 공구인선부 에서의 피삭재의 변위의 발달에 관한 모델이 제시되었고 파단변형도와 최대변형량과의 비교로부터 파단위치와 각도가 결정된다.

• 한국정밀공학회지
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• 제17권10호
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• pp.170-179
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• 2000

The objective of this study is to develop an analytical module for the prediction of burr formation during cutting process using the finite element method. This module is based on the rigid-plastic finite element method, ductile fracture criterion, fracture propagation technique and node separation criterion. The sequence of burr formation from burr initiation through end of burr formation is simulated and investigated by this module. The effect of material properties, such as AL6061-T6, AL2024-T4 and Copper, and cutting condition, such as rake angle and cutting depth, on burr formation is also discussed in this study. To validate this module the analysis results are compared with experimental ones.

• 한국임상수의학회지
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• 제19권4호
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• pp.405-410
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• 2002

The purpose of this investigation was to examine the effects of osteocalcin (serum bone GLA-protein, BGP) and procollagen carboxy-terminal propeptide (PICP) on new bone formation of canine fracture models. Serum osteocalcin and PICP were measured by standard RIA. The values of osteocalcin and PICP in the non-union and delayed-union fracture models were measured biweekly for 20 weeks in 14 dogs. The unions were radiographed for fracture healing. In non-union fracture group, the activity of BGP was markedly increased at four to eight weeks and decreased at twelve to twenty weeks and the activity of PICP was markedly increased at two to six weeks and slightly decreased at sixteen to twenty weeks. In delayed-union fracture group, the activity of BGP was markedly increased at two to eight weeks after treatment and maintained for the level until twenty weeks and the activity of PICP was markedly increased at two to six weeks after treatment and maintained for the level until twenty weeks. Radiologically, non-union group was not achieved until twenty weeks after fracture, delayed-union group was successfully achieved in eighteen weeks after fracture. These results suggested that the. activities of osteocalcin and PICP are useful parameters for biochemical markers of bone formation in dogs.

• 한국지반환경공학회 논문집
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• 제10권6호
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• pp.125-133
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• 2009

유체를 주입하여 암반을 파쇄하는 기술은 지열이나 석유 및 가스 등을 추출하는데 널리 사용되고 있는 방법이다. 본 기술을 적용 시 단일균열이 형성되면 이러한 에너지를 추출하는데 가장 이상적이다. 그러나 이러한 단일균열의 형성은 매우 드문 현상이며 분할된 형태의 균열생성이 흔한 현상이다. 이에 균열간 기계적 상호작용의 영향으로 설계변수에서도 단일균열을 가정하고 적용되었던 값과 차이를 보일 것으로 예상된다. 본 연구에서는 균열이 분할 생성되었을 경우 기계적인 상호작용을 고려할 수 있는 수치해석기법을 기존의 개발된 모델과 연계하여 설계변수인 길이, 균열폭, 그리고 압력을 계산하였다. 그 결과 균열의 형성은 이렇게 유체를 주입하여 암반을 파쇄 시 사용되는 설계변수에 상당한 영향을 끼치는 것으로 나타났다.

• 한국정밀공학회지
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• 제15권4호
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• pp.125-133
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• 1998

The objective of this study is to propose a new approach for modelling of burr formation process during orthogonal cutting when the tool exits the workpiece. This approach is based on the rigid-plastic finite element method combined with the ductile fracture criterion and the element kill method. This approach is applied to orthogonal cutting process to predict the fracture location and the fracture angle as well as the cutting force. To validate this approach, orthogonal cutting tests inside SEM(scanning electron microscope) at very low speed are carried out using A16061-T6 to observe the behavior of the material during the chip and the burr formation. The results of the experiment are compared with those of the finite element simulation.

• 한국세라믹학회지
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• 제35권6호
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• pp.551-558
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• 1998

Detection of microcrack in {{{{ {Al }_{2 } {O }_{3 } }} ceramics were studided by AE(acoustic emission) technique with 4-point bending test in order to evaluate the fracture process and formation of microcrack. Fully-dense alu-mina ceramics having a different grain size were fabricated by varing the hot-pressing temperature. The grain size of alumina increased with increasing the hot-pressing temperature whereas the bending strength decreasd. The microcracks were observed by SEM and TEM. The generation of AE event increased with increasing the applied load and many AE event was generated at maximum applied load. Alumina with smaller grain size shows the generation of many AE event resulting in an increase of microcrack formation. An intergranular fracture is predominantly observed in fine-grained alumina whereas intragranular fracture occurs predominantly in coarse-grained alumina,. Analysis of micorstructure and AE prove that primary mi-crocracks occur within grain-boundaries of alumina. The larger microcracking were formed by the growth and/or coalesence of primary microcracks. Then the materials become to fracuture by main crack gen-eration at the maximum applied load.

• 화약ㆍ발파
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• 제23권2호
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• pp.45-56
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• 2005

본 연구에서는 철근 콘크리트 기둥 발파시 수직하중과 철근의 영향에 따른 파쇄형태 및 파쇄체적에 대해 축소모형실험을 수행하였다. 수직하중이 증가할수록 수직하중에 의한 수직방향의 인장균열 및 철근에 의한 수직방향의 균열이 발생하였으며, 2.0톤에서는 수직방향의 인장균열이 철근에 의한 수직방향의 균열보다 우세하게 나타났다. 또한 수직하중이 증가할수록 수직방향의 인장균열이 우세하여 철근의 휨정도는 감소하였다. 발파공수가 증가하여도 수직하중에 따른 평균 파쇄체적은 크게 증가하지 않았으며, 이는 철근이 파쇄체적에 영향을 미치는 것으로 판단된다. 따라서 콘크리트 기둥 발파시 수직하중은 콘크리트의 파쇄형태와 철근의 휨정도에 중요한 영향을 미치며 철근은 파쇄체적에 영향을 미친다. 그러므로 철근 콘크리트 기둥 발파해체시 수직하중과 철근의 영향에 따라 천공패턴 및 발파패턴을 조절해야 한다.

• 펄프종이기술
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• 제41권2호
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• pp.13-19
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• 2009

In order to produce high quality paper at the lowest cost in high speed, typically various polyelectrolytes as retention aids were used. Retention systems such as single polymer system, dual polymer system, and microparticle system were used. The objective of this study was to analyze the changes of retention, drainage, formation and fracture toughness depending on types of retention system, molecular weight of C-PAM and dosage sequences of agents. When single polymer system was applied, retention was increased with poor formation and drainage. When common microparticle system(C-PAM/bentonite) was used, high molecular weight PAM gave high retention and fast drainage, but poor formation. When the microparticle system with reverse dosage sequence(bentonite/C-PAM) was used, low molecular weight PAM gave high retention, fast drainage and good formation. When various retention agents were applied, fracture toughness was increased than that of blank. When using high molecular weight PAM and consequently causing excessive flocculation, fracture toughness was decreased.

• 대한수의학회지
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• 제39권6호
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• pp.1197-1209
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• 1999

Twenty-one dogs(male 11 heads, female 10 heads) which were about 16 months ($16.3{\pm}3.5$) old and 10kg($10.1{\pm}2.0$) body weight, were allotted randomly into four groups as follows. Group I consisted of five dogs whose muscles were operated for sham muscle injuries. Group II consisted of seven dogs treated for cystic duct obstruction. Group III consisted of five dogs treated for the union fracture model. Group IV consisted of five dogs treated for the non-union fracture model. Radiographical and histological observations were carried out to determine bone alkaline phosphatase(BALP) and total alkaline phosphatase(TALP) values of each group for 20 weeks after the treatments with the condition of new bone formation. And also the applicability of percentage of BALP values to TALP (B/T) was studied after BALP was compared respectively with TALP. The level of TALP was increased without any relation to bone formation in group II, and all levels of BALP and B/T were increased in group III. The mean of B/T was high in statistical significance, due to varied levels of B/T and BALP. The changes of rates of B/T were significantly increased only in the case of the active new bone formation in group III, union fracture model. It was recognized that the mean values of B/T were statistical significant of the high applicability of the B/T ratio as an index of bone formation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.790-799
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• 2010

The Upper Devonian Grossmont Formation in Alberta, Canada reserves an estimated 50 billion cubic meters of bitumen and possess about 1/6 of the total bitumen resources in northern Alberta. However, unlike the overlying Athabasca oil sands, non conventional bitumen resources has not been developed as yet. The carbonate rocks of Grosmont Formation have been subject to various stages of diagenesis, including dolomatization and karstification with a strong effect on the distribution of porosity and permeability, which resulted in highly heterogeneous reservoirs. An extensive fracture logging and mapping was performed on total of six boreholes located in the study area to explore the characteristics of fracture geometry system and the subsurface structures of carbonates reservoir that holds bitumen. Fractal dimension was used as a measure of the statistical homogeneity of the fractured rock masses. The applicability of random Cantor dust, Dc, as a fractal parameter was examined systematically. The statistical homogeneity of fractured carbonates rock masses was investigated in the study area. The structural domains of the rock masses were delineated depthwise according to estimated Dc. The major fracture orientation was dominated by horizontal beddings having dip of $0-20^{\circ}$. Also, fractures having high dip angles existed with relatively low frequency. Three dimensional fracture network modeling for each structural domain has been performed based on fracture orientation and intensity, and some representative conceptual models for carbonates reservoir in the study area has been proposed. The developed subsurface conceptual models will be used to capture the geomechanical characteristics of the carbonates reservoir.