• Structural Engineering and Mechanics
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• v.62 no.1
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• pp.1-9
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• 2017

This paper describes laboratory tests carried out to evaluate the influence of class F fly ash (FA) on fracture toughness of plain concretes, specified at the third model fracture. Composites with the additives of: 0%, 20% and 30% siliceous FA were analysed. Fracture toughness tests were performed on axial torsional machine MTS 809 Axial/Torsional Test System, using the cylindrical specimens with dimensions of 150/300 mm, having an initial circumferential notch made in the half-height of cylinders. The studies examined effect of FA additive on the critical stress intensity factor $K_{IIIc}$. In order to determine the fracture toughness $K_{IIIc}$ a special device was manufactured.The analysis of the results revealed that a 20% FA additive causes increase in $K_{IIIc}$, while a 30% FA additive causes decrease in fracture toughness. Furthermore, it was observed that the results obtained during fracture toughness tests are convergent with the values of the compression strength tests.

• Tunnel and Underground Space
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• v.25 no.5
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• pp.450-461
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• 2015

Extensive numerical experiments have been carried out to investigate effect of block size and fracture geometry on hydraulic characteristics of fractured rock masses based on connected pipe flow in DFN systems. Using two fracture sets, a total of 72 2-D fracture configurations were generated with different combinations of fracture size distribution and deterministic fracture density. The directional block conductivity including the theoretical block conductivity, principal conductivity tensor and average block conductivity for each generated fracture network system were calculated using the 2-D equivalent pipe network method. There exist significant effects of block size, orientation, density and size of fractures in a fractured rock mass on its hydraulic behavior. We have been further verified that it is more difficult to reach the REV size for the fluid flow network with decreasing intersection angle of two fracture sets, fracture plane density and fracture size distribution.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.248-254
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• 2002

The most controversial topics in plasma sprayed ceramic coating system are recently mechanical properties such as bond strength, cohesive strength, toughness and so on. Determination of bond strength of coatings is one of the most important problems. In the industry, the bond strength of coating system has been estimated by Pull-off test(ASTM standard C633-79). But, without a fixed jig and specimen, it is impossible to obtain the bond strength. Therefore, it is necessary to study the critical fracture load on interface of the coating by indentation test. Because the critical fracture load plays an important role in evaluating the bond strength for plasma sprayed ceramic coating system. So, we have estimated critical fracture load in plasma sprayed ceramic coating system, and it was shown that inverse relationship between the cross-section hardness of coating and the critical fracture load(Pc). In case of the high load(1kgf, 2kgf) in $Al_{2}O_{3}+13%TiO_{2}$, it was found that the critical point(Pco), which the coating was broken on.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.737-742
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• 1994

The fracture energy of glass fiber/carbon fiber/epoxy resin hybrid composite system was investigated in the aspect of fracture mechanism. Epoxy resin matrix was DGEBA-MDA-SN-HQ system. On the interface of glass fiber and matrix, post debone friction energy provided a major contribution to the fracture energy, and debonding energy and pull-out energy were of the similar value. In the case of fracture on the interface of carbon fiber and matrix, pull-out energy was the major contributor.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.531-536
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• 2004

In fracture treatment with external fixators, the inter-fragmentary movements at the fracture site affect the fracture healing process, and these movements are highly related to the stiffness of external fixation systems. Therefore, in order to provide the optimal fracture healing at the fracture site, it is essential to understand the relationship between the stiffness and the system configurations in external fixation system. In this study we investigated the influences of system configuration parameters on the stiffness in the finite element analysis of an external fixation system of a long bone. The system alignment, the geometric and the material non-linearity of the pin, the joint stiffness and the callus formation were considered in the finite element model. In the first, the system stiffness of the developed finite element model was compared with the experiment data for model validation. The consideration of the joint stiffness and nonlinearity of the model improved the system stiffness results. The joint stiffness, the non-alignment of the system decreased the system stiffness while the callus formation increased the system stiffness. The present results provided the biomechanical basis of rational guidelines for design improvements of external fixators and pre-op. planning to maximize the system stiffness in fracture surgery.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.11 no.1
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• pp.69-77
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• 1989

This is a retrospective study on 219 patients with mandibular fracture. The patients were treated in the Dept. of Oral Maxillofacial Surgery of WON KWANG UNIV. HOSPITAL from Aug. 1, 1984 to Sept. 30. 1988. The results were as follows. 1. The mandibular fractures occured most frequently in the twenties(35%) and male were predominant (74.7%) than females. 2. The most frequent etiologic factor was traffic accident(34.3%). 3. The most common location of fracture was symphysis(37.1%). And angle(27.6%), condyle(25.7%), ramus(1.6%) were next in order of frequency. 4. In mandible fracture, they have an average 1.8 fracture line. 5. The use of plate & screw system were more increased in the comparison of each year. 6. Intermaxillary fixation period was more reduced from the concept of 6 weeks fixation, due to the use of Plate & screw system. 7. Postoperative acute wound infection was developed 9.6% in 219 mandibular fracture patients. The compression osteosynthesis was most common cause of acute wound infection than any other treatment method. 8. Postoperative malocclusion was developed 4% in 219 mandibular fracture. And the compression osteosynthesis was most common cause of malocclusion. 9. Acute wound infection was detailed by the approach method. The Intraoral & extraoral combination method was most common cause on acute infection and intraoral, extraoral approach method was next in order of frequency. 10. Normal mouth opening process was proportioned to IMF period. The short IMF period have a fast normal mouth opening process.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.5
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• pp.488-492
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• 2010

This review evaluates the literature on the relationship between mandibular condylar process fracture and temporomadibular joint (TMJ). The topic of condylar fracture generated more discussion and controversy than any other field of maxillofacial trauma associated with TMJ. Disturbance of occlusal function, devia-tion of mandible, internal derangements of TMJ, and ankylosis of the joint with resultant inability to move the jaw are sequelae of condylar process fracture. Thus it is necessary to understand how the masticatory system adapts to the structural alterations that accompany fractures of the mandibular condyle. Treatment of condylar process fracture include two methods ; closed treatment and open treatment. If one chooses totreat closed, one must understand that adaptations in the musculature, skeleton, and dentition will be necessary. Open treatment of condylar process fractures probably requires fewer adaptations within the masticatory system to provide a favorable functional outcome. However, one must weigh the risk of open surgery against the possible improvement in outcome. The risks are not just surgical risk, but biological risk as well, such as disruption of the blood supply to the condyle. This review presents relevant aspects of change of TMJ associated with condylar process fracture.

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.283-291
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• 2015

The purpose of this study was to investigate effects of TiN coating on the fatigue fracture of dental implant system with various cyclic loads. TiN coated abutment screw, the fixture, and abutment of internal hex type were prepared for fatigue test. The fatigue test was carried out according to ISO 14801:2003(E) using tensile and compression tester with repeated load from 30% to 80% of static fracture force. Morphology and fractured surface was observed by field emission scanning electron microscope(FE-SEM) and energy dispersive X-ray spectroscope(EDS). The fracture cycle drastically decreased as repeated load increased. Especially, in the case of TiN-coated abutment screw, fracture cycle increased compared to non-coated abutment screw. The fatigue crack was propagated fast as repeated load increased. The plastic deformation region decreased, whereas, cleavage fracture region increased as repeated load increased.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.146-151
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• 2012

The present article shows how the fracture strength of single crystal silicon chips, which are generally used as semiconductor devices, is influenced by loading rate variation during a 3-point bending test. It was found that the fracture strength of the silicon chips slightly increases up to 4% with increasing loading rate for loading rates lower than 20 mm/min. Meanwhile, the fracture strength of the chips hardly increases with increase of loading rate to levels higher than 40 mm/min. However, there was an abrupt transition in the fracture strength within a loading rate range of 20 mm/min to 40 mm/min. This work explains through microscopic examination of the fracture surface of all test chips that such a big transition is related to the deflection of crack propagation direction from the (011) [${\bar{1}}00$] system to the (111) [${\bar{2}}11$] system in a particular loading rate (i.e. from 20 mm/min to 40 mm/min).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.1903-1910
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• 2001

The BI(Ball Indentation) method has a potential to assess the mechanical properties and to replace conventional fracture tests. In this study, the BI test system has been developed to evaluate material properties. Tensile tests, fracture toughness tests, hardness tests and BI tests were performed by the system using four classes of thermally aged specimens. The results of the BI tests were in good agreement with fracture characteristics from a standard fracture test method.