• Archives of Reconstructive Microsurgery
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• v.11 no.1
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• pp.1-10
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• 2002

Purpose : To analyze the clinical results of free vascularized osteocutaneous fibula graft to tibial defect combined with soft tissue defect and infection. Materials and Methods : In the retrospective study of 51 consecutive cases of vascularized osteocutaneous fibular graft, the length of the grafted fibula, size of the skin flap, anastomosed vessels, ischemic time of the flap, time for union, hypertrophy of fibula and the complications were evaluated. Results : Initial bony union of the grafted fibula was obtained at 3.74 months after operation, except 4 cases of nonunion and delayed union. The weight bearing without external supports was possible at 18 months after operation in average. The fracture of grafted fibula was most common complication(16 cases). Conclusion : The vascularized osteocutaneous fibula graft provided satisfactory bony union and functional results in the cases not responsible for conventional treatment methods.

• Archives of Reconstructive Microsurgery
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• v.15 no.2
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• pp.77-84
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• 2006

Purpose: We present clinical usefulness of saphenous neurocutaneous island flap for reconstruction of soft tissue defect of the lower leg, especially anteromedial aspect, including foot and ankle. Materials and Methods: Thirteen cases of soft tissue defects in the lower leg including foot and ankle which were 6 cases of pretibial area, 2 cases of anteromedial aspect of distal two third, 2 cases of ankle, and 3 cases of foot were treated saphenous neurocutaneous island flap. They were proximally based flap 3 cases and distally based flap 10 cases. Clinically the flaps ranged in size from $4{\times}5\;cm$ to $6{\times}12\;cm$. Results: All of the flaps except 1 case survived completely. Three cases, however, had marginal necrosis. One case of flap failure was proximal tibia fracture accompanied with injury of the flap pedicle which was difficult in flap elevation, subsequently. Conclusion: The saphenous neurocutaneous island flap is a simple, reliable procedure with a versatility for soft tissue coverage of the lower leg, especially anteomedial aspect, including foot and ankle. In case of another injuries accompanied near the saphenous nerve, careful attention should be made.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.50-58
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• 2008

The SM45C metallic coupons have been tested under static tensile loading with acoustic emission (AE) as the load-deflection curve mainly. In this study, we used AE to detect the yielding of material and AE techniques was applied to rapidly estimate the mechanical characteristics of a material. First, coupons without an artificial defect were tested at different cross-head speed. For all cases in this analysis, yielding point of SM45C coupons did not appear definitely compared to mild steel, whereas coupons start to generate AE counts upon yielding. So all cases are normalized to know the possibility of accelerated life test of a material. And next, coupons with different from sizes of circular hole defects were tested at the same cross-head speed of 5 mm/min. Results were classified into 3 classes and analyzed by AE amplitude & signal strength as a function of time. Summarizing the specific conclusions, we need to additional research considering plate with width-ratio in order to estimate the fracture mechanism.

• Korean Journal of Materials Research
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• v.14 no.6
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• pp.379-388
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• 2004

To investigate the effect of D-ferrite on the hot workability and surface defect of STS 304 billets containing 3 wt. % Cu, microstructure observations and high temperature mechanical properties test were carried out for the specimens extracted mainly from raw or oxidized billets. It was found that the total $\delta$-ferrite content has little influence on the hot workability, even though the fracture cracks due to high temperature tension or compression test were initiated and propagated mostly along $\delta$/${\gamma}$ boundary in the specimens. On the other hand, it was supposed that the direct causes of surface defects in the wire rolled from the as-continuously cast billet were the grain boundary embrittlement arose from the deep diffusion of oxygen into the grain boundary, and the oxidation of $\delta$-ferrite connected by a grain boundary to the surface during the billet reheating process as well.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.6 s.249
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• pp.722-727
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• 2006

Bone fracture healing is one of the important topics in biomechanics, demanding computation simulations due to the difficulty of obtaining experimental or clinical results. In this study, we adopt the design space optimization method which was established by the authors as a tool for the simulation of bone growth using its evolutionary characteristics. As the mechanical stimulus, strain energy density is used. We assume that bone tissues over a threshold strain energy density will be differentiated and bone tissues below another threshold will be resorbed. Under compression and torsion as loadings, the filling process of the defect is well illustrated following the given mechanical criterion. It is shown that the design space optimization is an excellent tool for simulating the evolutionary process of bone growth, which has not been possible otherwise.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.2
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• pp.83-90
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• 2005

Failure cause of the fractured engine parts was analyzed by microstructural observation. These parts were failed far earlier than the expected service life. By the stereoscope and SEM examinations of the fractured surface, the fracture modes have been identified as wear and fatigue failure. From the observation of microstructure and microhardness measurements of the failed gears, the probable cause for failures are internal oxidation during using and retained austenite and carbide networks due to heat-treatment, respectively. These defected structures at near surface contributed to the wear and fatigue failure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1058-1062
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• 1996

The assessments of weld defects by fracture mechanics are performed for design of welded Joints. In general, butt, T-type, and L-type welded joint are useful for welding structure. When linear weld defects are in welded joint, stress intensity factors for each joints are calculated by finite element method. Analysis results are shown for the fracture modes and characteristics of joint types. And they are founded for the weaken order of welded joints being T-type, butt, L-type.

• Structural Engineering and Mechanics
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• v.14 no.2
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• pp.191-208
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• 2002

A comparative assessment study for a generation of the pressure-temperature (P-T) limit curve of a reactor vessel is performed in accordance with ASME code. Using cooling or heating rate and vessel material properties, stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during reactor cool-down and heat-up. P-T limit curves are analyzed with respect to defect orientation, clad thickness, toughness curve, cooling or heating rate and neutron fluence. The resulting P-T curves are compared each other.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.93-109
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• 2015

Finite element analysis (FEA) combined with the concepts of linear elastic fracture mechanics (LEFM) provides a practical and convenient means to study the fracture and crack growth of materials. In this paper, a numerical modeling of crack propagation in the cement mantle of the reconstructed acetabulum is presented. This work is based on the implementation of the displacement extrapolation method (DEM) and the strain energy density (SED) theory in a finite element code. At each crack increment length, the kinking angle is evaluated as a function of stress intensity factors (SIFs). In this paper, we analyzed the mechanical behavior of cracks initiated in the cement mantle by evaluating the SIFs. The effect of the defect on the crack propagation path was highlighted.

• Advances in materials Research
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• v.12 no.4
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• pp.273-286
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• 2023

The fracture mechanics make it possible to characterize the behavior with cracking of structures using parameters quantifiable in the sense of the engineer, in particular the stress field, the size of the crack, and the resistance to cracking of the material. Any structure contains defects, whether they were introduced during the production of the part (machining or molding defects for example). The aim of this work is to determine numerically by the finite element method the stress concentration factor Kt of a plate subjected to a tensile loading containing a lateral form defect with different sizes: a semicircle of different radii, a notch with different opening angles and a crack of different lengths. The crack propagation is then determined using the extended finite element technique (X-FEM). The modeling was carried out using the ABAQUS calculation code.