• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.11
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• pp.880-885
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• 2010

The Angle Ring and Cap which is called pressboard are settled at the primary and secondary coil winding of 154 kV transformer that can reduce effectively distance of insulation. As it has not manufactured pressboard of Angle Ring and Cap for high voltage grade, insulation components industry especially high voltage transformer has not participate in a competition with worldwide yet. That's why is difficult to make an specialized shape of insulation components of high voltage grade. Therefore it has finally completed to make an deformation manufacturing utility using an bellowed special analysis tools. This study that uses various analysis program determining optimum shape about insulation of Angle Ring and Cap which is related life of high voltage transformer. In addition to develop forming equipment with an specialized five steps pressing. That is also based on the mechanical strength evaluation and test, it is investigated optimized processing components.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.597-600
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• 2003

Bi-2223/Ag HTS wires have been fabricated by the PIT(powder in tube)process. Intermediate annealing was carried out to increase the homogenization and uniformity of the superconducting filaments embedded in the silver matrix during the deformation process that is important to sustain the engineering critical current density in long superconducting wire. Intermediate annealing act to release the deformation hardening of the superconducting wires during drawing process. Rolling parameters were investigated to roll the superconducting tapes with uniform thickness, width and winding tensions. Critical current of 60 m long superconducting tapes was measured 54.3 A continuously after final sintering heat treatment. The phase analysis of Bi-2223/Ag superconducting tapes are examined by the XRD.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.351-354
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• 2002

In most of electrical applications using Bi-2223/Ag HTS tapes, bending and tension stresses are essentially applied to the tape. Therefore, the critical current of the Bi-2223/Ag tape is degraded by increasing the deformation stress, though brittle superconducting filaments are embedded in the reinforced Ag alloy sheath. It is needed to understand bending and tension properties of HTS tapes at room temperature and cryogen to make superconducting magnet, cable and etc. using Bi-2223/Ag HTS tapes. Actually, bending and tension stress applied to the tapes simultaneously, when winding the tapes on former for applications. In this study, the effect of mechanical deformations, bending and tension, on the critical current of Bi-2223/Ag tape was investigated.

• Composites Research
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• v.18 no.4
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• pp.66-74
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• 2005

This paper reports new repair and strengthening mathod using improved material. This mathod have two type according to covering thickness of reinforcement. One type is near surface mounted FRP rod. Anther type is overay. Fiber Reinforced Plastic (FRP) materials has become very popular in recent years. FRP material used to rehabilitate many types of structures with superior characteristics such as high strength and stiffness and corrosion resistance. This strengthening mathod were used FRP rod which have better bond and shear strangth than current FRP rod. Development of FRP rod due to 3-D winding system. In addition, Ductile hybrid FRP has a certain plastic deformation and an elongation greater than 3% at maximum load is usually required for steel reinforcement in concrete structures. Moerover this mathod can be effective repair of base concrete by sprayed polymer mortar.

• Clean Technology
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• v.16 no.4
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• pp.245-253
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• 2010

Optimum conditions for UV-radiated photopolymerization of unsaturated polyester that could be used as protecting layer of large diameter pipe were investigated in this paper. UV photopolymerization method was selected to solve the problems, arising when thermal polymerization by organic peroxide was used, such as the instability of peroxide initiator, the evolution of volatile organic compound, and thermal deformation of product. Two of the photo-initiators (Irgacure 819 and Darocure 1173) well known for its penetrating ability deep into the polymer layer were selected, and the optimum conditions for photopolymerization (1.5 phr initiator content, 1:1.2 initiator ratio, Ga lamp for UV source) were found from the thermal and mechanical test results of the resultant UP polymers. In addition, composite materials containing UP polymer and glass fiber were tested for hardness, impact strength, and flexural strength to find that the impact strength of composite significantly improved.

• Composites Research
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• v.21 no.3
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• pp.9-17
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• 2008

In this paper, the low velocity impact characteristics of filament winding CFRP pressure vessel was investigated using numerical and experimental methods. The cylinder part of CFRP vessel was impacted using triangular shape impactor which simulated the sharp edge of dropping tools and impact response behavior of CFRP was reviewed. The mechanical behavior, such as deformation and stress distribution, were also predicted by explicit finite element method and the validity of the model was investigated. For the quantitative evaluation of the residual strength of the pressure vessel after impact, a series of the ring specimens was cut from the impacted vessel and its burst pressure was measured by hydraulic pressure hoop tension test. As the results, the relationship between the residual strength degradation and the impact energy was successively obtained and a useful methodology to evaluate quantitatively the impact damage tolerance of CFRP pressure vessel was established.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.519-529
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• 2009

Fiber reinforced composite materials have various advantages in mechanical and chemical aspects. Not only high fatigue and chemical resistance, but also high specific strength and stiffness are attained, and therefore, damping characteristics are beneficial to marine piles. Since piles used for marine structures are subjected to compression and bending as well, detailed research is necessary. Current study examine the mechanical behavior under flexural and/or compressive loads using concrete filled fiber reinforced plastic composite piles, which include large size diameter. 25 pile specimens which have various size of diameters and lengths were fabricated using hand lay-up or filament winding method to see the effect of fabrication method. The inner diameters of test specimens ranged from 165 mm to 600 mm, and the lengths of test specimens ranged from 1,350 mm to 8,000 mm. The strengths of the fill-in concrete were 27 and 40 MPa. Fiber volumes used in circumferential and axial directions are varied in order to see the difference. For some tubes, spiral inner grooves were fabricated to reduce shear deformation between concrete and tube. It was observed that the piles made using filament winding method showed higher flexural stiffness than those made using hand lay-up. The flexural stiffness of piles decreases from the early loading stage, and this phenomenon does not disappear even when the inner spiral grooves were introduced. It means that the relative shear deformation between the concrete and tube wasn't able to be removed.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.4
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• pp.1-10
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• 2004

The purpose of this study is to investigate the flexural behavior of square concrete filled carbon tube (CFCT) columns subjected to constant axial load with the cyclic lateral load. Two parameters, wnding angle and thickness of tube, were chosen to evaluate the flexural capacity and behavior of rectangular CFCT columns. Selected two parameters were considered simultaneously in order to evaluate the flexural behavior of a rectangular CFCT columns more precisely. Flexural strength, deformation capacity, ductility and energy dissipation capacity of rectangular CFCT columns were evaluated by calculating the area of load-displacement envelope curves and load-dispalcement hysteresis curves obtained from experiment. Also, the ductile capacity obtained from experiment was compared to that of reinforced masonry wall for the comparison of existing structural element.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.2
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• pp.41-50
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• 2021

The asphalt pavement industry has introduced the warm-mix asphalt (WMA) as a mean of energy saving and environmentally safe technology, because the WMA mixture can be mixed and compacted at 30℃ lower than conventional hot-mix asphalt (HMA) at 160℃ or higher. The implementation of WMA can be a good option for paving operations for rural road in remote place, not only due to energy saving and environmental issues, but also lower working temperature. Using WMA technology, the cooled-down asphalt mixture can be still compacted to meet the quality requirement in narrow winding rural road in remote places. Therefore, this study is designed to evaluate engineering properties of WMA binders and concretes, which were prepared for rural road pavement. The objective of the study was to evaluate and suggest proper fundamental properties level of the WMA concrete for rural road pavement. The kinematic viscosity test result indicated that the WMA binders used in this study were effective for compaction at lower temperature, i.e., at 115℃, compared to the HMA binder. According to strength property analyses, it was found that the WMA concrete was acceptable for rural road pavement even though it was compacted at 30℃ lower level. Since the deformation strength (SD) of 3.2 MPa was found to satisfy rutting and cracking resistance minimum guidelines, this value was suggested as a minimum SD value for rural road pavement, considering lack of maintenance program for rural area.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.245-248
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• 2005

During manufacturing thick composite cylinders, large thermal residual stresses are developed and induce catastrophic interlaminar failures. Since the residual stresses are dependent on many process parameters, such as temperature distribution during cure, cure shrinkage, winding tension, and migration of fibers, calculation of the residual stresses is very difficult. Therefore a radial-cut method have been used to measure the residual stresses in the composite cylinders. But the conventional radial-cut method needs to know numerous material properties which are not only troublesome to obtain but also vary with change of fiber arrangement during consolidation. In this paper, a new radial-cut method with cut-cylinder-bending test was proposed and the measured residual stresses were compared with calculated thermal residual stresses. It was found that the new radial-cut method which does not need to know any of material properties gave better estimation of residual stresses regardless of radial variation of material properties. Additionally, interlaminar tensile strength could be obtained by the cut-cylinder-bending test.