• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.113-132
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• 2005

The purpose of this study was to assess the stress-induced pattern at the supporting bone, the implant fixture, the abutment and the abutment screw according to a friction-fit joint (Astra; Model 1) or slip- fit joint (Frialit-2; Model 2) in the internal connection system under vertical and inclined loading using finite element analysis. In conclusion, in the internal connection system of the implant and the abutment connection methods, the stress-induced pattern at the supporting bone, the implant fixture, the abutment and the abutment screw according to the abutment connection form had difference among them, and the stress distribution pattern usually had a widely distributed tendency along the inner surface of the implant fixture contacting the abutment post. The magnitude of the stress distributed in the supporting bone, the implant fixture, the abutment and the abutment screw was higher in the friction-fit joint than in the slip-fit joint. But it is considered that the further study is necessary about how this difference in the magnitude of the stress have an effect on the practical clinic.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.965-971
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• 2001

The objective of this study is to investigate the characteristics - microstructure, hardness, adhesive strength and friction coefficient - of the coatings with aging - treatment after optimizing internal- plasma spraying parameters for Al-30wt%Si powder as a basic research to manufacture the cylinder block bore for Al engine composed of Al-30wt%Si alloy on Al alloy, The optimum internal-plasma spraying parameters of Al-30wt%Si alloy are summarized as follows: voltage: 37.5V, current: 160A, working distance: 25mm, gun traverse speed: 4.5mm/s, rotating speed: 518m/min. The primary Si particles grew aggressively with increasing heat-treating temperature. The hardness of the as-sprayed coating was about Hv=275 but this value was abruptly decreased with increasing heat-treating temperature. And average friction coefficient of the coating was below 0.08 after heat treatment for 48h at $175^{\circ}C$.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.53-59
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• 2008

The purpose of the study was to evaluate how much gastropod shell effected its properties better than crushed stone as coarse grained materials by comparing friction properties of a contact surface between coarse grained materials and geosynthetics with the large-scale direct shear test. To achieve the purpose, the study compared and analyzed friction coefficient and friction angle by making crushed stone or gastropod shell into model ground and by installing and shearing non-woven fabric or geostrip geosynthetics. As the results of the analysis, crushed stone had the internal friction angle of $33.8^{\circ}$ when its unit weight was $13.7kN/m^3$ and gastropod shell had the internal friction angle of $35.4^{\circ}$ when its unit weight was $5.4kN/m^3$. Also, the friction angle of a contact surface between geosynthetics and crushed stone was larger than the friction angle of a contact surface between geosynthetics and gastropod shell.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.9-13
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• 2003

The objective of this study is structural analysis of rope brake for elevator. The finite element model was developed to compute the stress, strain and friction force for rope brake. The ANSYS code was used for this analysis. In order to structural analysis of rope brake, many variables such as internal pressure, boundary condition, load condition and constraints were considered.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.1
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• pp.89-94
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• 2005

The objective of this study is structural analysis of rope brake by spring type. The finite element model was developed to compute the stress, strain and friction force for rope brake by spring type. The ANSYS code was used for this analysis. In order to structural analysis of rope brake, many variables such as internal pressure, boundary condition load condition and constraints were considered.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.150-155
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• 2004

The objective of this study is structural analysis of rope brake by spring type. The finite element model was developed to compute the stress, strain and friction force for rope brake by spring type. The ANSYS code was used for this analysis. In order to structural analysis of rope brake, many variables such as internal pressure, boundary condition, load condition and constraints were considered.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.265-270
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• 2002

Dilatancy is a unique characteristics of granular materials showing the tendency to change volume upon shearing. In this study large triaxial tests were peformed for both the well graded rock and the poorly graded rock. And the shear strength of rockfill materials considering dilatancy is evaluated based on the test results. For the rock materials of this study the contribution of dilatancy in the maximum internal friction angle is as much as -6.0%∼3.0% of the internal friction angle measured at peak

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.89-99
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• 2008

In this paper, the position tracking control problem of the servo system with nonlinear dynamic friction is issued. The nonlinear dynamic friction contains a directly immeasurable friction state variable and the uncertainty caused by incomplete parameter modeling and its variations. In order to provide the efficient solution to these control problems, we propose the composite control scheme, which consists of the robust friction state observer, the FNN approximator and the approximation error estimator with sliding mode control. In first, the sliding mode controller and the robust friction state observer is designed to estimate the unknown internal state of the LuGre friction model. Next, the FNN estimator is adopted to approximate the unknown lumped friction uncertainty. Finally, the adaptive approximation error estimator is designed to compensate the approximation error of the FNN estimator. Some simulations and experiments on the servo system assembled with ball-screw and DC servo motor are presented. Results show the remarkable performance of the proposed control scheme. The robust friction state observer can successfully identify immeasurable friction state and the FNN estimator and adaptive approximation error estimator give the robustness to the proposed control scheme against the uncertainty of the friction parameters.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.207-213
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• 2001

Shaking table tests to investigate the dynamic friction behavior of interfaces between dense dry granular soils and construction material(concrete) were performed and the results are reported. The results show the variation of dynamic interface friction coefficients between dense dry granular soils and construction material was small in the sliding velocity range employed in this study. It was also observed that dynamic interface friction coefficients decreased as mean grain sizes of granular soils increased. These coefficients were compared with the friction coefficients obtained from the peak internal friction angles of the same granular soils by plane strain compression tests.

• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.33-40
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• 2015

Volcanic rocks in Jeju Island indicate the differences in geological and mechanical characteristics from region to region, and have vesicular structure caused by various environmental factors. In this study, triaxial compressive strength tests were conducted for intact rocks sampled in northeastern onshore and offshore, southeastern offshore and northwestern offshore of Jeju Island. The estimated cohesion and internal friction angle from the results of triaxial compression tests were compared and analyzed with absorption, a parameter representing the vesicular properties of basalts in Jeju Island. As a result, it was found that the relationship between cohesion and absorption could be classified clearly, considering two different linear relationships in bulk specific gravity and absorption. As the absorption increases, the cohesion decreases exponentially. In addition, the internal friction angle decreases almost linearly with increasing in the absorption, regardless of the relationships in bulk specific gravity and absorption.