• 대한지하수환경학회지
• /
• 제5권2호
• /
• pp.80-87
• /
• 1998

지하수의 유동로가 시설의 성능에 미치는 영향이 큰 방사성폐기물처분시설에서는 암반블럭규모의 흐름은 단열망개념으로 해석하고 있다. 본 연구는 연구지역의 지하수유동 해석을 위하여 3차원 투수성단열망모델을 구축하기 위한 것으로서, 단열의 기하학적 인자 및 수리인자에 대한 확률분포함수를 도출하고, 3차원 단열망모델링과 수리시험 결과를 이용한 모델 교정까지의 과정을 포함한다. 구간별 정압주입시험의 결과를 Cubic law로서 해석한 결과 단열투수량계수는 lognormal분포일 때 6.12$\times$$10^{－7}$ $m^2$/sec이다. 부정류해석에 의한 유동차원은 주로 방사상 내지 구상유동 특성을 보인다. FracMan 코드를 이용해서 추정된 투수성단열밀도는 1.73이고, 이때 암반블럭규모(l00 m$\times$100 m$\times$100 m)로 모사된 투수성단열의 수는 3,080개이다.다.

• Composites Research
• /
• 제13권4호
• /
• pp.75-82
• /
• 2000

유리섬유/에폭시 복합재료로 피막한 유리판의 표면파괴거동을 연구하기 위하여 미소강구 충격실험을 수행하였다. 본 연구에서는 다섯 종류의 재료, 단순소다유리판(soda-lime glass plates), 유리섬유/에폭시박막(glass/epoxy lamina)을 1층 접착, 비접착한 시편과 박막을 3층 접착, 비접착한 시편을 사용하였다. 충격속도 범위 40∼120m/s에서 유리판 배면에서의 최대 응력과 흡수파괴에너지를 측정하였다. 충격 속도증가에 따라 링균열, 콘균열, 레이디얼 균열이 시편 내부에서 발생하였다. 복합재료 박막으로 피막한 결과, 소다유리판의 균열은 현저히 감소하였으며 측정한 최대 응력과 흡수파괴에너지를 이용하여 표면 파괴거동 특성을 평가할 수 있었다.

• Interaction and multiscale mechanics
• /
• 제4권1호
• /
• pp.35-47
• /
• 2011

A global-local finite element modeling technique is employed in this paper to predict the fatigue life of radial truck tires. This paper assumes that a flaw exists inside the tire, in the local model. The local model uses an FEM fracture analysis in conjunction with a global-local technique in ABAQUS. A 3D finite element local model calculates the energy release rate at the belt edge. Using the analysis of the local model, a study of the energy release rate is performed in the crack region and used to determine the crack growth rate analysis. The result considers how different driving conditions contribute to the detrimental effects of belt separation in truck tire failure. The calculation of the total mileage on four sizes of radial truck tires has performed on the belt edge separation. The effect of the change of belt width design on the fatigue lifetime of tire belt separation is discussed.

• 한국생산제조학회지
• /
• 제9권2호
• /
• pp.87-95
• /
• 2000

By using AIP(Arc Ion Plating) of a physical vapor deposition for the first time in Korea a ceramic tool whose surface is coated single layeredly with TiN is developed. In addition cutting resistance appearing in the process of finishing cut of hardened carbon tool steel STC3 is studied. The principal and radial components of cutting resistance in those cutting conditions appear to be the same or similar and the feed component is relatively small. The feed component is found to be in proportion to cutting width and the radial component in proportion to cutting thickness. Owing to coating the cutting resistance of a TiN coated ceramic tool increas-es compared with that of a general ceramic tool.

• The Korean Journal of Ceramics
• /
• 제7권2호
• /
• pp.63-69
• /
• 2001

We investigated strength degradations from cyclic contact fatigue in self-toughened glass-ceramics. Hertzian indentation was used to induce cyclic contact load. Dynamic fatigue was also performed with changing stress rates from 0.01 to 10000 MPa/sec. After that, strength data and fracture origins were analysed. As the number of contact cycles increased or stressing rate decreased, severe strength degradation occurred by as much as 50% because of radial cracks developed from microcrack coalescence.

• Clinics in Shoulder and Elbow
• /
• 제17권1호
• /
• pp.25-30
• /
• 2014

Background: Normal elbow joint kinematics has been widely studied in cadaver, whilst in vivo study, especially of the forearm, is rare. Our study analyses, in vivo, the kinematics of normal forearm and of malunited forearm using a three-dimensional computerized simulation system. Methods: We examined 8 patients with malunited Monteggia fracture and 4 controls with normal elbow joint. The ulna and radius were reconstructed from CT data placing the forearm in three different positions; full pronation, neutral, and full supination using computer bone models. We analyzed the axis of rotation 3-dimentionally based on the axes during forearm rotation from full pronation to full supination. Results: Axis of rotation of normal forearm was pitch line, with a mean range of 2 mm, from full pronation to full supination, connecting the radial head center proximally and ulnar fovea distally. In normal forearm, the mean range was 1.32 mm at the proximal radioulnar joint and 1.51 mm at the distal radioulnar joint. However in Monteggia fracture patients, this range changed to 7.65 mm at proximal and 4.99 mm at distal radoulnar joint. Conclusions: During forearm rotation, the axis of rotation was constant in normal elbow joint but unstable in malunited Monteggia fracture patients as seen with radial head instability. Therefore, consideration should be given not only to correcting deformity but also to restoring AOR by 3D kinematics analysis before surgical treatment of such fractures.

• 대한치과보철학회지
• /
• 제31권4호
• /
• pp.482-505
• /
• 1993

The purpose of this study was to evaluate the fracture characteristics and the effect of resin bonding of laminate porcelain. In order to characterize the indentation-induced crack, Young's moduli and characteristic indentation dimensions were measured. The fatigue life under three point flexure test was measured using the electro-dynamic type fatigue machine, and the crack propagation with thermocycling was investigated on the condition of 15 second dwell time each in $5^{\circ}C\;and\;55^{\circ}C$ bath. The Vickers indentation pattern and the fracture surface were examined by an optical microscope and a scanning electron microscope (SEM). The results obtained were summarized as follows ; 1. Young's moduli(E) of the laminate porcelain and the resin cement used in this experiment were $62.56{\pm}3.79GPa$ and $15.01{\pm}0.12GPa$, respectively. 2. The initial crack size of the laminate porcelain was $69.19{\pm}5.94{\mu}m$ when an indentation load of 9.8N was applied, and the fracture toughness was $1.065{\pm}0.156MPa\;m^{1/2}$. 3. The fatigue life of laminate porcelain showed the constant fracture range at the stress level 27.46-35.30MPa. 4. When a cyclic flexure load was applied, the fatigue life of resin-bonded laminate porcelain was more decreased than that of laminate porcelain. 5. When a thermocycling was conducted, the crack growth rate of resin-bonded laminate porcelain was more increased than that of laminate porcelain. 6. Fracture surface showed the radial crack, the lateral crack, and the macroscopic crack branching region beneath the plastic deformation region when an indentation load of 9.8N was applied.

• 한국임상수의학회지
• /
• 제25권3호
• /
• pp.215-217
• /
• 2008

Medical records from the Veterinary Medical Teaching Hospital of the University of Missouri-Columbia from 2004 to 2007 were available for 28 raptors that underwent long bone fracture repair. There were 14 owls, 10 hawks, 2 vultures, 1 eagle, and 1 falcon. Mean body weight was 780 g (ranged from 150 to 1400 g) for 14 owls; 650 g (ranged from 150 to 1270 g) for 10 hawks; 1760 g (ranged from 1520 to 2000 g) for 2 vultures; 5000 g for 1 eagle; and 130 g for 1 falcon. Of all 28 fracture cases, 11 cases (39%) and 1 case (3%) were related to hit-by-car and shooting respectively. Physical examination revealed dehydration in 18 raptors (64%) and lethargy in 12 raptors (42%). Forty one long bone fractures were included in 28 cases. The radiographs revealed 13 ulnar fractures (32%), 12 humeral fractures (30%), 10 radial fractures (25%), 4 tibiotarsal fractures (9%), 1 femoral fracture (2%), and 1 fibular fracture (2%). External skeletal fixation using polymethylmethacrylate (PMMA) combined with intramedullary fixation was used in 19 long bone fractures (46%). Intramedullary fixation using intramedullary Kirschner pin was used in 16 long bone fractures (39%). No surgical treatment was performed in 6 long bone fractures (15%). This study reported that many of raptors presented dehydration and lethargy when admitted for treatment. Therefore, proper hydration and nutrition are critical pre-surgical requirements. In addition, combination of internal fixation and external skeletal fixation using PMMA might be better option to treat raptors with comminuted fracture that results from mostly trauma of hit-by-car.

• International Journal of Precision Engineering and Manufacturing
• /
• 제4권1호
• /
• pp.30-36
• /
• 2003

Brittle materials such as glasses and ceramics, which are very weak under impact loading, show fragile failure mode due to their low fracture toughness and crack sensitivity. When brittle materials are subjected to impact by small spheres, high contact pressure occurs at the impacted surface causing local damage on the specimen. This damage is a dangerous factor in causing the final fracture of structures. In this research, the crack propagation process of soda-lime glass by the impact of small spheres is explained and the effects of several constraint conditions for impact damage were studied by using soda-lime glass; that is, the effects for the materials and sizes of impact ball, thickness of specimen and residual strength were evaluated. Especially, this research has focused on the damage behavior of ring cracks, cone cracks and several other kinds of cracks.

• 대한기계학회논문집A
• /
• 제26권1호
• /
• pp.153-159
• /
• 2002

Brittle materials such as ceramics and glasses show fragile fracture due to the low toughness and the crack sensitivity. When brittle materials are subjected to impact loading by small spheres, high contact pressure occurs to the surface of the specimen. Local damage is subsequently generated in the specimen. This local damage is a dangerous factor which gives rise to the final fracture of structures. In this research, impact damage of soda-lime glass plates by small spheres was evaluated by considering the effects of impact directions of indenter, pressure condition of specimen and residual strength after impact loading.