• International Journal of Korean Welding Society
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• v.4 no.1
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• pp.53-60
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• 2004

Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5mm/min. As a result, the load distribution showed a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.4
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• pp.127-134
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• 2021

In this study, the adhesive fracturing characteristics of a DCB specimen due to single and heterogeneous bonding materials under tearing load was investigated. The experiments were conducted to examine the fracturing properties of the adhesive DCB specimen. As an experimental condition, a forced displacement of 3mm/min was applied to one side while the other side was fixed. As a result of the experiment, it was found that the AL6061-T6 material was superior to the CFRP material in terms of maximum stress, specific strength, and energy release rate when compared to the adhesive fracturing property of a single material. We tested CFRP-AL, a heterogeneous bonding material, and compared its experimental results to the results from the single materials. Based on these results, CFRP-AL with a heterogeneous bonding material was observed to have the superior structural safety compared to single materials for the mode III fracture type.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.682-697
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• 2001

This investigation evaluated the fracture toughness($K_{IC}$) of eight currently available core materials, and relate the fracture toughness value to fractography analysis and surface characteristics using a atomic force microscope (AFM). Single-edge notched (SEN) test specimens (n=10) and compact tension (CT) test specimens (n=10) were prepared conforming to the ASTM Standard E-399 for a high copper amalgam, three composite core materials (Core-Max II, Core Paste, Bisfil Core), two reinforced composite core materials (Ti-Core, Ti-Core Natural), a resin-modified glass ionomer core material (Vitremer), and a conventional glass ionomer core material (Ketac-Molar). The specimens were tested with an Instron Universal Testing Machine. The maximum loads were measured to calculate the fracture toughness ($K_{IC}$). Thereafter, fracture surfaces of SEN specimens of each material were investigated for fractography analysis using scanning electron microscope. And, disc-shaped specimens with 1mm thickness were fabricated for each material and were investigated under AFM for surface morphology analysis. The results were as follows: 1. Bisfil Core showed the highest mean fracture toughness regardless of test methods. 2. For the tooth-colored materials, Ti-Core Natural exhibited the highest fracture toughness. 3. Ketac Molar showed a significantly low fracture toughness when compared with the amalgam and the composite resin core materials(p<0.05). 4. The fracture toughness values obtained with the single-edge notched test, except Ketac Molar, were higher than those obtained in the compact tension test. 5. SEM revealed that the fracture surface of high fracture toughness material was rougher than that of low fracture toughness material. 6. AFM revealed that the surface particles of the composite resins were smaller in size, with a lower surface roughness than the glass ionomer core materials.

• Imaging Science in Dentistry
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• v.39 no.2
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• pp.93-98
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• 2009

Purpose: To classify and evaluate the mandibular fractures. Materials and Methods : The author classified the mandibular fractures of 284 patients who were referred to the Chonbuk National University Dental Hospital during the period from March 2004 to June 2007. This study was based on the conventional radiographs as well as computed tomographs which were pertained to the 284 patients who have had the mandibular fractures including the facial bone fractures. And mandibular fractures were classified with respect to gender, age, site and type of the fractures. Results: More frequently affected gender with mandibular fracture was male with the ratio of 3.3:1. The most frequently affected age with mandibular fracture was third decade (38%), followed by fourth decade (16%), second decade (15%), fifth decade (11 %), sixth decade (7%), seventh decade (5%), eighth decade (4%), first decade (4%), and ninth decade (0.3%). The most frequent type of mandibular fracture was single fracture (58%), followed by double fracture (39%), triple fracture (3%). The most common site of mandibular fracture was mandibular condyle as 113 cases (27.7%) and the next was mandibular symphysis as 109 cases (26.7%), mandibular angle as 103 cases (25.3%), mandibular body as 83 cases (20.3%) in order. The sum of fracture sites were 408 sites and there were 1.4 fracture sites per one patient. The number of mandible fractures accompanied with facial bone fractures were 41 cases (14.4%). Conclusion: The results showed the most frequent type and common site of mandibular fracture was single fracture and mandibular condyle respectively. (Korean J Oral Maxillofac Radiol 2009; 39: 93-8)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.728-731
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• 1995

Miniaturzed specimen technology permits mechanical bechanical behavior to be determined using a minimum volume of material. because it is almost impossible to sample the conventional specimen for the fracture toughness test without damage to the rotor. In addition, it is different to collect a large amount of actual turbine rotor steels. Hence seven kinds of specimen with different degradation levels were prepared by isothermal aging heat treatment at 630 .deg. C. Test material was 1Cr-1Mo-0.25V steel which was widely used for turbine rotor material. The relation between fracture toughness and DBTT was investigated The characteristics of minaturized impact speciments technique was discussed. Finally, the estimating method of fracture toughness using a single impact specimen was introduced.

• Journal of the Korean GEO-environmental Society
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• v.7 no.5
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• pp.79-87
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• 2006

This paper presents the numerical model developed to simulate the solute transport in rough and smooth single fractures. The roughness of these fractures is represented by using the fractal surface method. In this study, the 3D transport model, which is based on the random walk technique, is used to simulate the dispersion process of a solute which is represented by numerical particles. As the simulation results, it can be observed that the dispersion of solute in the fracture is significantly affected by the fracture roughness and particle size.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.36-43
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• 1999

The effect of microstructure on the fracture toughness of multi pass weld metal has been investigated. The micromechanisms of fracture process are identified by in-situ scanning electron microscopy(SEM) fracture observation using single edge notched specimen. The notches of the in-situ fracture specimens were carefully located such that the ends of the notches were in the as-deposited top bead and the reheated weld metal respectively. The observation of in-situ fracture process for as-deposited top bead indicated that as strains are applied, microcracks are formed at the interfaces between soft proeutectoid ferrite and acicular ferrite under relatively low stress intensity factor. Then, the microcracks propagate easily along the proeutectoid ferrite phase, leading to final fracture. These findings suggest that proeutectoid ferrite plays an important role in reducing the toughness of the weld metal. On the other hand, reheated regions showed that the microcrack initiated at the notch tip grows along the localized shear bands under relatively high stress intensity factor, confirming that reheated area showing momogeneous and fine microstructure would be beneficial to the fracture resistance of weld metal.

• Proceedings of the KSEEG Conference
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• 1999.04a
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• pp.90-93
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• 1999

We present a high frequency electromagnetic (EM) inversion scheme for detecting and characterizing a fracture using single-hole data. At high frequencies, say above tens of mega-hertz, since displacement currents cannot be ignored, electrical permittivity as well as electrical conductivity is to be considered together for analyzing the EM scattering data. In this paper, we have developed a three-step inversion scheme to map the fracture and to evaluate its electrical conductivity and permittivity. We performed EM profiling along the z-axis using three-component receivers for each source. The model was excited by a vertical magnetic dipole and the resistant magnetic fields were inverted using the non-linear least-squares method. Background resistivity and permittivity were easily obtained using vertical magnetic fields below 1 MHz and above 10 MHz, respectively. Both the vertical and dipping sheets were successfully mapped using the phase difference between 40 and 41 MHz. The electrical property of the sheet was well resolved using the information obtained in the previous two steps and secondary magnetic fields. Our study shows the potential of imaging the fracture in single-hole survey environment using the high frequency EM method.

• Journal of Veterinary Clinics
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• v.33 no.2
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• pp.124-128
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• 2016

A 7-year-old intact female Maltese dog presented with a history of bite wounds. Physical examination revealed labored breathing, four puncture wounds with subcutaneous emphysema of the thorax, and paradoxical respiratory movement of the right thoracic wall. On radiography, a segmental fracture of the right 7th rib and a single fracture of the 8th rib were evident on the dorsal thorax. An inward displacement of the fractured segment and contusion of the right caudal lung lobe were identified with computed tomography. A diagnosis of pseudo-flail chest was made. Exploratory thoracotomy revealed a full-thickness muscular defect, a marked discoloration of the right caudal lung lobe, a segmental fracture of the right 7th rib, and a single fracture of the right 8th rib. Necrotic tissues were removed using surgical debridement. The fractured 7th and 8th ribs were corrected using a single interfragmentary wiring technique. The thoracic wall was reconstructed using the latissimus dorsi muscle flap. Additional thoracic stabilization using a thermoplastic splint was applied to correct paradoxical respiratory movement. The external splint was removed 4 weeks postoperatively. There was no evidence of respiratory abnormalities 18 months postoperatively.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.645-654
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• 1989

Specimens of WC-Co were indented to measure the resulting crack size and unindented samples were fractured in 3-point flexure to obtain the strength and to measure characteristic features on the fracture surface. Fracture toughness was determined using fractography and compared to those determined using identation techniques. We show that principles of fracture mechanics can be applied WC-Co composites and can be used to analyze the fracture process. The fracture surfaces were examined by scanning electron microscopy and optical microscopy. Characteristic feature observed in glasses, single crystals and polycrystalline materials known as mirror, mist, hackle, and crack branching were identified for these composites. We discuss the importance of fracture surface analysis in determining the failure-initiating sources and the failure behaviorof WC-Co composites.