• 한국세라믹학회지
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• 제35권12호
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• pp.1257-1265
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• 1998

Hertzian contact tests were used to investigate the evolution of fracturedamage in the coating layer as functions of contact load and coating thickness by studying crack patterns in porcelain on glass-infiltrated alumina bilayer system conceived to simulate the crown structure of a tooth. Cone cracks initiated at the coating top surface without delamination at interface and crack propagation to substrate. Preferentially the cracks made multi-cracks at the coating top surface rather than proceeding to interface. The cracks were highly stabilized with wide ranges between the loads to initiate first cracking and to cause final failure im-plying damage-tolerant capability. Finite element modelling was used to evaluate the stress distribution. Maximum tensile stress were responsible for the cracking at the coating layer and had a profound influence on the crack pattern and fracture damage in the layered structure materials.

• 한국안전학회지
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• 제35권5호
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• pp.9-14
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• 2020

In order to realize high strength and light weight for various industrial facilities and structural materials, various new materials are applied to product design. Among them, CFRP has excellent specific strength and non-rigidity, and the scope of use is expanding throughout the industry, such as mobility products and building materials. GFRP is cheaper than CFRP, and has excellent specific strength and non-rigidity, and has excellent heat resistance and sound insulation, so it has been adopted as a core material for flooring and interior flooring. CFRP of twill weave structure has better resistance to deformation of fiber than plain weave structure, so the outermost layer is applied as twill weave structure in product design. After fabrication with DCB specimens, Mode I fracture toughness was evaluated according to the crack length. As the crack length increases, the energy release rate and stress intensity factor values tended to decrease overall.

• Journal of Korean Dental Science
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• 제6권1호
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• pp.4-12
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• 2013

Purpose: This study sought to verify the usefulness of mini-implant and surgical steel wire in the treatment of mandibular fracture through the objective identifi cation of the change of bone structure and bone density before and after reduction by evaluating radiological change through fractal analysis when mandibular fracture is treated using mini-implant and surgical wire. Materials and Methods: This study looked at 45 patients (males: 38, female: 7) diagnosed with mandibular fracture in the oral and maxillofacial surgery division of Chung-Ang University Dental Hospital and who received open reduction and intra-osseous fi xation. Result: The average fracture dimension values were higher for the group of the patients who had mini-implants and surgical wire treatment. Conclusion: Based on the results of the study on the usefulness of the reduction technique using mini-implant and surgical steel wire in the treatment of mandibular fracture through the fractal analysis method, the reduction technique using mini-implant and surgical steel wire is regarded as an effective method of minimizing the gap between mandibular fracture fragments.

• 한국안전학회지
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• 제32권6호
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• pp.9-15
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• 2017

Recently many researches were conducted on the interlaminar fracture that is a delamination between laminates by using ASTM standardized methods. However the experiment of the intralaminar a fracture is difficulty. In this study, four types of CFRP/GFRP composites with different layer structures were compared to evaluate an intralaminar fracture toughness under the mode I. Also the CNTs were added to the layer for the examination of the fracture toughness improvement. And the characteristics of the crack propagation behaviour was observed using a microscope. The obtained results can be useful for the evaluation of the intralaminar fracture toughness of the CNT reinforced CFRP/GFRP composites.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.790-791
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• 2006

The fracture behavior and mechanical characteristics of sintered rare-earth magnets were investigated. It shows that the fracture behavior and bending strength of the magnets obviously exhibit anisotropy. Sm-Co magnets tend to cleavage fracture in the close-packed (0001) plane or in the ($10\bar{1}1$) plane. The fracture mechanism of $Nd_2Fe_{14}B$ magnet mainly appears to be intergranular fracture. The anisotropy of fracture behavior and mechanical strength of sintered rare-earth magnets is caused mainly by the strong crystal-structure anisotropy and the grain alignment texture. The effects of Nd content, and Pr, Dy substitution on the impact stability of $Nd_2Fe_{14}B$ magnets were also reported.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.583-586
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• 2000

In this paper, the embedded crack approach that crack is modeled by discontinuous line inside finite element is applied for localized progressive fracture analyses. The algorithm for progressive fracture analyses of concrete structure are enhanced by introducing nonlinear softening curve and unloading algorithm of tension-softening curve which can simulate localized fracture of concrete. The failure analysis results ar compared with existing test results for varification.

• Computers and Concrete
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• 제32권1호
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• pp.99-117
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• 2023

The crack under the influence of the higher intensities of the stresses grows and the structure gets collapsed with the time when the crack length reaches to critical value. Therefore, the fracture behavior of a structure in terms of stress intensity factors (SIF) becomes important to determine the remaining fracture strength and capacity of material and structure for avoiding catastrophic failure, increasing safety and further improvement in the design. The robustness of the method has been demonstrated by comparing the numerical results with analytical and experimental results of some problems. XFEM is used to model cracks and holes in structures and predict their strength and reliability under service conditions. Further, XFEM is extended with a stochastic method for predicting the sensitivity in terms of output COVs and fracture strength in terms of mean values of stress intensity factors (SIFs) of a structure with discontinuities (cracks and holes) under tensile loading condition with input individual and combined randomness in different system parameters. In stochastic technique, the second order perturbation technique (SOPT) has been used for the predicting the fracture behavior of the structures. The stochastic/perturbation technique is also known as Taylor series expansion method and it provides the reliable results if the input randomness is less than twenty percentage. From the present numerical analysis it is observed that, the crack tip near to the hole is under the influence of the stress concentration and the variational effect of the input random parameters on the crack tip in terms of the SIFs are lesser so the COVs are the less sensitive. The COVs of mixed mode SIFs are the most sensitive for the crack angles (α=45° to 90°) for all the values of c₁ and d₁. The plate with the shorter distance between hole and crack is the most sensitive with all the crack angles but the crack tip which is much nearer to the hole has the highest sensitivity.

• Journal of International Society for Simulation Surgery
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• 제1권1호
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• pp.16-18
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• 2014

The orbit has a very special anatomical structure. The complex anatomical structure should be restored when we encounter the patient with orbital wall fracture. Unless these specific anatomy were reconstructed well, the patient should suffer from various complications such enophthalmos, diplopia or orbital deformity. In addition, because the patient has a his own specific orbital shape, individualized approach will be necessary. The aim of this trial is to try to restore the original orbit anatomy as possible based on the mirrored three dimensional CT images based on the computer simulation. Preoperative computed tomography (CT) data were processed for the patient and a rapid prototyping (RP) model was produced. At the same time, the uninjured side was mirrored and superimposed onto the traumatized side, to create a mirror-image of the RP model. In order to restore the missing skipped images between the cuts of CT data because of the thinness of the orbital walls, we manipulated the DICOM data for imaging the original orbital contour using the preoperatively manufactured mirror-image of the RP model. And we fabricated Titanium-Medpor to reconstruct three-dimensional orbital structure intraoperatively. This prefabricated Titanium-Medpor was then inserted onto the defected orbital wall and fixed. Three dimensional approach based on the computer simulation turned out to be very successful in this patient. Individualized approach for each patient could be an ideal way to manage the traumatic patients in near future.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.284-287
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• 2005

The flow of groundwater in fractured medium is related to the geometric characteristics of the fracture system. And a fracture aperture and a fracture density are considered as important factor concerning the permeability. Data acquisition of the properties of fracture such as aperture and density is so difficult and has uncertainty. We also cannot know the fracture characteristics through the in-situ tests. We usually obtain the fracture information from a ultrasonic scan logging or borehole television indirectly. Using the deduced results, we can make the fracture system and simulate the groundwater flow and solute transport in the crystalline rock. This study aimed to analyze the correlation between the properties of fracture and hydraulic conductivities obtained at the same interval. The properties of fracture are examined by acoustic televiwer and hydraulic conductivities are obtained by constant Pressure injection test. The distributioin of fracture width and fracture frequency shows the log-normal probability plot. And, Results of correlation analysis explain that opened type fractures have proper relation with hydraulic conductivity. But, as though there are semi-opened type fractures or closed type fractures, those have the permeable structure.

• 대한족부족관절학회지
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• 제2권2호
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• pp.71-75
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• 1998

The fact that, under similar training activities performed in the same environment, march fractures develop in only a certain percentage of the trainees indicates that intrinsic factors are affecting the prevalence of these fractures. Among these intrinsic factors, the relation between foot arch type and the occurance of march fractures was investigated in this study. From 1997 to 1998, at one infantry medical company of infantry corps in Korea, 15 march fracture patients were detected among infantry soldiers. Quantitative measures of the foot arch (longitudinal) structure of 15(30feet) march fracture patients were established and compared with those of 15(30feet) normal person. The results were as follows. 1. From the lateral X-ray film, three parameters (i.e. calcaneal angle, forefoot angle, height to length ratio)were defined to describe the structure of the longitudinal arch of the foot. 2. The mean value of the calcaneal angle of march fracture group and normal control group showed 16.4 degree, 20.5 degree respectively. The difference between two groups was statistically significant (P>0.006), but those of forefoot angle and height to length ratio were not. 3. In the calcaneal angle twenty-six feet(87%) of march fracture group were lower than 17 degrees but twenty-five feet(83%) of normal control group were more than 17 degrees. That is, march fracture were more prevalent in feet with low calcaneal angle. 4. In the low arch foot, the orthotic device might relieve the energy load carried by the foot, thus reducing the incidence of march fractures, and should be analyzed in further study.