• International Journal of Highway Engineering
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• v.15 no.1
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• pp.23-36
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• 2013

PURPOSES: The problem under this circumstance is that the erosion not only drops strength of the steel dowel bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem, alternative dowers bars are developed. METHODS: In this study, the bearing stresses between the FRP tube dowel bar and concrete slab are calculated and compared with its allowable bearing stress to check its structural stability in the concrete pavement. These comparisons are conducted with several cross-sections of FRP tube dowel bars. Comprehensive laboratory tests including the shear load-deflection test on a full-scale specimen and the full-scale accelerated joint concrete pavement test are conducted and the results were compared with those from the steel dowel bar. RESULTS: In all cross-sections of FRP tube dowel bars, computed bearing stresses between the FRP tube dowel bar and concrete slab are less than their allowable stress levels. The pultrusion FRP-tube dowel bar show better performance on direct shear tests on full-scale specimen and static compression tests at full-scale concrete pavement joints than prepreg and filament-winding FRP-tube dowel bar. CONCLUSIONS: The FRP tube dowel bars as alternative dowel bar are invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Also, the pultrusion FRP-tube dowel bar performed very well on the laboratory evaluation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.255-261
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• 2000

Tube bending is one of the conventional manufacturing process. Recently, tube bending was highlighted in automotive industry by hydroforming. Tube hydroforming process is divided into pre-bending process and hydroforming process. It's initial state is very important in die cavity of first hydroforming process. So tube bending is important factor of the hydroforming process. In this paper, two pre-bending simulations, by a rotary draw bending machine and a bend die. This paper presents the simulation results in pre-bending process that is used to form an automotive part, tie-bar.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.80-83
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• 1997

The split Hopkinson bar technique is the most widely used method to study material behavior at high strain rate deformation. In the present paper, a torsional Hopkinson bar for testing thin-walled tube specimens at high strain rate is described. From the experiment of aluminum 6061, dynamic stress-strain relationship can be obtained and dynamic result is compared with static one.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1168-1173
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• 2003

When the tube contacted to support and antivibration bar of the steam generator in unclear power plant, the contact area is worn out by their relative displacement. In the study, wear depths of the tube inclined to tube support and antivibration bar are approximately predicted by a method using the contact load and relative displacement. In the case of the inclined contact, the results show wear depths of the steam generator tube predicted by the impact model are larger than those by the sliding model.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.4
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• pp.295-300
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• 2016

In the design of passive and active boring bars, the structural dimensions and shape of the vibration control boring bar are modified depending on the diameter and depth of the workpiece, which changes the dynamic behavior. Thus, the natural frequency, effective mass, and stiffness for the main structure of a tube-type boring bar need to be reset for each vibration control case. However, commercial finite element method (FEM) software and experimental modal analysis are mostly used at present despite being too time-consuming. To overcome the weaknesses of the two methods currently used for vibration control, we realized a graphical user interface (GUI) program for the modal analysis of a modified tube-type damping structure. The analysis results with the GUI program were compared to those with commercial FEM software in order to confirm the effectiveness of the former.

• The Journal of Advanced Prosthodontics
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• v.4 no.4
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• pp.254-258
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• 2012

Implant-supported overdenture is a reliable treatment option for the patients with edentulous mandible when they have difficulty in using complete dentures. Several options have been used for implant-supported overdenture attachments. Among these, bar attachment system has greater retention and better maintainability than others. SFI-Bar$^{(R)}$ is prefabricated and can be adjustable at chairside. Therefore, laboratory procedures such as soldering and welding are unnecessary, which leads to fewer errors and lower costs. A 67-year-old female patient presented, complaining of mobility of lower anterior teeth with old denture. She had been wearing complete denture in the maxilla and removable partial denture in the mandible with severe bone loss. After extracting the teeth, two implants were placed in front of mental foramen, and SFI-Bar$^{(R)}$ was connected. A tube bar was seated to two adapters through large ball joints and fixation screws, connecting each implant. The length of the tube bar was adjusted according to inter-implant distance. Then, a female part was attached to the bar beneath the new denture. This clinical report describes two-implant-supported overdenture using the SFI-Bar$^{(R)}$ system in a mandibular edentulous patient.

• The Journal of Advanced Prosthodontics
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• v.3 no.1
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• pp.47-50
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• 2011

Despite the greater retention and low maintenance of bar attachment system, the longer clinical time and increased number of visits were the assignments to overcome in bar attachment system. This case report describes SFI-Bar$^{(R)}$ (Cendres et Me$\'{e}$taux, Biel/Bienne, Switzerland) to be solve those problems. A 65-year-old female, who had severely absorbed mandible, hoped to wear a stable mandibular denture without pain. As soon as two implants were placed on mandible, a tube bar was connected to two adaptors connected to each implant. The length of the tube bar was adjusted considering inter implant distance, and reconnected to the adaptors. Finally a female part was seated beneath the denture. This case report showed that a satisfactory clinical result was achieved by delivering bar overdenture immediately after implant placement without laboratory procedure.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.934-938
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• 2003

Flow analyses using FLUENT 5.4 code were performed to validate the application of the local bidirectional flow tube in case of water and air flow. In this study, sensitivity studies have been performed to optimize the design features of the bi-directional flow tube which can be applied for the various experimental conditions. 2-dimensional axisymmetric steady state flow analyses have been performed. By calculating the differential pressure at both the front and the rear hole of the flow tube, K values were evaluated. The K values show good linearity regardless of the tube sizes and the Re numbers in both water and air flow. And system pressure and water subcooling didn’'t affect the K values. Under the elevated pressure of 80bar with 80K water subcooling, the K value indicates a similar trend with the case of 2bar with 80K water subcooling.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.84-89
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• 2004

When the tube contacted to support, anti-vibration bar of the steam generator in nuclear power plant, the contact area is worn out by their relative displacement and contact force. Connors and Au-Yang found the relation between tube worn displacement and volume, or normal work rate at given gap size. The present analysis is obtained the relation between tube worn displacement and normal work rate at various gap size modifying Au-Yang's result. The results are compared with Connors and Yettisir and Pettigrew's results. The comparison shows that Yettisir and Pettigrew result is fairly good agreement with Connors and present results with gap clearance, 0.015in.

• Coupled systems mechanics
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• v.11 no.4
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• pp.315-333
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• 2022

Fluid-Structure Interaction (FSI) modeling is highly effective to reveal deformations, fatigue failures, and stresses on a solid domain caused by the fluid flow. Mechanical properties of the solid structures and the thermophysical properties of fluids can change under different operating conditions. In this study, we investigated the interaction of [45/-45]₂ wounded composite tubes with the fluid flows suddenly pressurized to 5 Bar, 10 Bar, and 15 Bar at the ambient temperatures of 24℃, 66℃, and 82℃, respectively. Numerical analyzes were performed under each temperature and pressure condition and the results were compared depending on the time in a period and along the length of the tube. The main purpose of this study is to present the effects of the variations in fluid characteristics by temperature and pressure on the structural response. The variation of the thermophysical properties of the fluid directly affects the deformation and stress in the material due to the Wall Shear Stress (WSS) generated by the fluid flow. The increase or decrease in WSS directly affected the deformations. Results show that the increase in deformation is more than 50% between 5 Bar and 10 Bar for the same operating condition and it is more than 100% between 5 Bar and 15 Bar by the increase in pressure, as expected in terms of the solid mechanics. In the case of the increase in the temperature of fluid and ambient, the WSS and Von Mises stress decrease while the slight increases of deformations take place on the tube. On the other hand, two-way FSI modeling is needed to observe the effects of hydraulic shock and developing flow on the structural response of composite tubes.