• Proceedings of the KSME Conference
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• 2001.06a
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• pp.932-938
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• 2001

This study is concerned with the shape optimization of stem for the artificial hip prosthesis with unbonded cement mantle. The artificial hip prosthesis with unbonded cement mantle allows a stem to slip on cement mantle because of polished stem surface. Unbonded cement mantle type has several advantages compared with bonded cement mantle type, for example, small micro motion, preventing stress shielding and so on. In this study, 2-dimensional axisymmetric model was developed with considering characteristics of unbonded cement mantle. Moreover, optimal shape of stem was obtained by using feasible direction method. The objective of this optimization is maximizing supported vertical loading. The slip motion and stresses of stem, cement mantle and bone is used for constraints. The optimal shape which obtained by this study has slope of 0.15 in proximal part and maintains the width about 5mm in distal part In addition, simplified 3-dimensional analysis which applying optimal shape is carried out. The result of 3-dimensional analysis showed that optimal shape has some advantages for cement mantle stress. However, more realistic 3-dimensional analysis which including bending effect, complex geometries etc. is needed in further research.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.951-955
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• 2001

The experimental comparison between bonded and unbonded types stem-cement interface was carried out on axisymmetric stem-cement-aluminum model of the femoral component of a total hip replacement. Human femur was modeled in non-tapered and tapered($7.5^{\circ}$) aluminum hollow cylinders to emulate the diaphyseal and metaphyseal segments of the femur. For unbonded type, we tested stems with three different taper angles($5^{\circ},\;7.5^{\circ},\;10^{\circ}$). In every case, the cement-aluminum interface was designed to endure 8MPa shear strength. (a measured value at cement-bone interface) We tested aluminum models under axial loading for both cases. As an experimental result, it was found that unbonded stem sustained more axial load as bonded stem in both cases, diaphyseal and metaphyseal models. The unbonded types failed in cement mantle under axial compressive load, while the bonded ones failed in shear at cement-aluminum interface. These results suggest that a polished stem will sustain much higher axial load than a roughened stem. And a polished stem will make more stable cement-bone interface that may promote better osteosythesis around the stem.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.530-534
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• 2001

Many dental practitioners are bonding amalgam to tooth structure. The potential advantage of this procedure, suggested by in vitro test results, are reduced microleakage, which could lead to a reduced incidence of postoperative sensitivity ; increased strength of the prepared tooth ; and retention of restoration in less retentive preparations, with the potential fer conserving tooth structure. Although in vitro studies support this procedure, its efficacy has not been adequately confirmed in the clinical environment. The authors placed traditional Class I and Class II, bonded and unbonded amalgam restorations in 76 teeth. Fuji I Glass Ionomer luting cement was the bonding agent selected. Marginal adaptation were evaluated after two years. the authors found no significant difference in marginal adaptation between bonded and unbonded restorations.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.145-148
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• 2004

The purpose is to prove the newly established 'UNBONDED CAPPING' method for Concrete Strength Tests. Day by day, concrete buildings and structure became high-rising and magnificently vast scheduled, as contributed from the development of improved equipments that suitable to specific construction works and high qualitied Admixture, the qualities of the concrete was highly improved. It is very important that the concrete strength tests and evaluation should be carried out in the manner that as soon as the concrete is placed so that dismantling form works can be done in time and that may enabling reducing construction period directly related with the costs of the project. However, the conventional capping method of concrete specimen requires more manpower and consuming times, As for the Sulfur capping, there may be incurred accidential fire and generation of Gas, what is more there stands limitation in precise evaluation of strength test results because of variation in capping method results may vary in concrete strength test results. Not necessarily emphasize, the compression strength of the concrete is the most valuable basic data essential to control the qualities of the concrete and that should be carried out accurately. in this study evaluation of the compressive strength test results comparing stabilized concrete capping method for Cement Paste capping, Sulfur-paste capping ,High Gypsum capping and recently flowing the Grinding with the UNBONDED CAPPING' method to provide reliable and economical concrete strength testing.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.635-642
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• 1997

This research focused on the development of concrete overlay and test, which was conducted at 88 Highway 105k, 2 lanes of 290 m. The field application test consists of 6 cm and 10 cm bonded concrete overlay and 25 cm unbonded concrete overlay, using the slag cement for opening lanes for traffic early. The overlay were placed in a day. The whole period of traffic closing wes 8 day and it was reopened to traffic after concrete overlay has cured for 3 day. 5 cracks were founded when the field test section was investigated after 1 month, but all these may not make significant problems to overlay because these initiated and growed at the same line of repair section. The rideability and skid resistance become much better like in the new pavement after overlay. The structural capacity against deflection was much. which were verified by FWD(Falling Weight Deflectometer). The field test section is being used in a good condition and the results of field application and pavement performance analysis are encouraging. This rehabilitation methods may be adopted in Korea after a more field performance verifications.

• Structural Engineering and Mechanics
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• v.63 no.3
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• pp.361-370
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• 2017

Through the use of finite element analysis and acoustic emission techniques we have evaluated the interfacial failure of a carbon fiber reinforced polymer (CFRP) repair patch on a notched aluminum substrate. The repair of cracks is a very common and widely used practice in the aeronautics field to extend the life of cracked sheet metal panels. The process consists of adhesively bonding a patch that encompasses the notched site to provide additional strength, thereby increasing life and avoiding costly replacements. The mechanical strength of the bonded joint relies mainly on the bonding of the adhesive to the plate and patch stiffness. Stress concentrations at crack tips promote disbonding of the composite patch from the substrate, consequently reducing the bonded area, which makes this a critical aspect of repair effectiveness. In this paper we examine patch disbonding by calculating the influence of notch tip stress on disbond area and verify computational results with acoustic emission (AE) measurements obtained from specimens subjected to uniaxial tension. The FE results showed that disbonding first occurs between the patch and the substrate close to free edge of the patch followed by failure around the tip of the notch, both highest stress regions. Experimental results revealed that cement adhesion at the aluminum interface was the limiting factor in patch performance. The patch did not appear to strengthen the aluminum substrate when measured by stress-strain due to early stage disbonding. Analysis of the AE signals provided insight to the disbond locations and progression at the metal-adhesive interface. Crack growth from the notch in the aluminum was not observed until the stress reached a critical level, an instant before final fracture, which was unaffected by the patch due to early stage disbonding. The FE model was further utilized to study the effects of patch fiber orientation and increased adhesive strength. The model revealed that the effectiveness of patch repairs is strongly dependent upon the combined interactions of adhesive bond strength and fiber orientation.