• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.149-154
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• 2004

For a present study, we investigated fatigue behavior of cracked aluminum repaired by unidirectional graphite/epoxy composite material. Three different specimens were used in the fatigue tests: cracked aluminum, cracked aluminum repaired by graphite/epoxy composite patch, and plasma-treated aluminum repaired by graphite/epoxy composite patch. The surface of the aluminum was treated using a DC plasma. The results showed that the fatigue crack growth behavior of cracked aluminum was significantly improved by repairing the cracked area with a composite patch. Specifically, the specimen repaired by composite patch showed about 300％ more fatigue lift than the cracked aluminum. In particular, the plasma-treated aluminum repaired by composite patch showed almost 12 ％ more fatigue life than the cracked aluminum repaired by graphite/epoxy composite patch. The increased fatigue life of plasma-treated case was attributed to the surface roughness of aluminum by plasma treatment.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.21-27
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• 2019

Composite motor cases fabricated by the filament winding method are structurally weak in the dome when they are required to withstand the internal pressure of the combustion gas. In this study, a finite element analysis is conducted to compare the burst pressure of a composite dome according to the variation of the pressure distribution ratio(PDR). The performance of the composite motor case was compared quantitatively by calculating the stress on the inner and outer dome surfaces and metal boss volume. As a result, the critical point of the failure mode was observed at a PDR between 2.5 and 3.0. A design at a PDR of 2.5­-3.5 can reduce the weight of metal boss without fluctuation in the burst pressure of the combustion motor case. Moreover as the design reference value changes according to the dome shape and opening size, further analysis and testing are necessary.

• The magazine of the Korean Society for Advanced Composite Structures
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• v.3 no.1
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• pp.33-39
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• 2012

• Journal of Welding and Joining
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• v.14 no.5
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• pp.78-86
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• 1996

Vision sensor was used to track the weld line of the compressor case. The compressor case was fixed in jig equipped with the rotating system, and two torches having one degree of freedom was applied in automatic welding system. The radius of rotation for the compressor case is varying with each rotating angle, while, the angle velocity is constant Therefore, an algorithm to extract the feature of the compressor case for varying rotation angle is needed. To over come the avove difficulties, the curve fitting and composite curve were used. The experiment to verify the proposed algorithm showed desirable results for tracking the welding line of compressor case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.799-807
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• 1999

Exergy analysis is widely used in energy system analysis for more efficient energy use. Pinch technology has focused on chemical plants, such as pure heat exchanger networks. In this study, the objective is to seek more effective means with integrating above two methods. In order to demonstrate effective result and to prove possibility for pinch analysis, the steam turbine is adopted to make heat recovery in the heat exchanger network. Three cases are introduced using the integration of exergy and pinch analysis. The standard steam turbine utility is the base case, and adding the heat pump to this system is the second case. The third case is the system with the heat pump and minimum utilities. The results show that the output power of steam turbine in the case(2) and case(3) are increased up to 42% and 46%, respectively, compared with that of base case.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.629-634
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• 2000

Comparing with single structure constructed with reinforced concrete or steel, composite structures have a great advantage. However, in case of nuclear power structure, the application of a conventional single structure (reinforced concrete or steel structure) inflicts a heavy loss on a economical and constructive efficiency. But, the application of composite slab to nuclear power structure could compensate these deficiency. Therefore, in this study, the structural behavior of composite slab in nuclear power structure is observed to assure economical and constructive efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.275-284
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• 1997

Thermodynamic behavior of a composite system which is composed of two simple thermal subsystems with constant heat capacities is analyzed, and several thermodynamic phenomena are investigated. The changes of the states and the potential work of the composite system are shown as the interaction between the subsystems in the composite system. The potential work is defined as the possible maximum available work from the composite system, and it is a thermodynamic property of the composite system. The decrease of the potential work is the same as the available work output from the composite system in reversible processes. The dissipation of available work is directly connected to the generation of entropy. The concepts of exergy and internal energy can be explained as a special case of the potential work.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.109-117
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• 2012

This study seeks to devise a design application for a beam structure with partially restrained composite connection to a CFT column. A cost-efficient and stable component is applied by adjusting the stiffness ratio of the column connection through partially restrained composite connection. Based on a review of the structure's stability, it was confirmed that in the case of a low-rise building as a moment frame, resistance without bracing is feasible because stiffness increased by virtue of the partial restrained composite connection by composite action. In the case of a high-rise building, lateral resistance load of moment frame was approximately 10% when proper partial restrained rate was at around 60%. With considerations related to economic efficiency, the partial restriction effect of the beam component was significantly activated by the uniform load, but that of the beam activated by concentrated load was not significantly indicative. The analysis indicated that 60% partial restrained girder at the connection was the most economical in the case of uniform load. It also showed that end moments can be reduced by approximately 25%.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.321-337
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• 2000

Dental caries, one of the most frequent dental disease, become larger because it can be thought as a simple disease. Further more, it can progress to unexpected root canal therapy with fabrication of crown that needs reduction of tooth structure. Base is required in a large caries and ZOE, ZPC, glass ionomer are used frequently as base material. They, with restorative material, can affect the longevity of the restoration. In this study, we assume that the mandibular 1st molar has deep class I cavity. So, installing the 3 base material, 3 kinds of fillings were restored over the base as follows; 1) amalgam only, 2) amalgam with ZPC, 3) amalgam with ZOE, 4) amalgam with GI cement, 5) gold inlay with ZPC, 6) gold inlay with GI cement, 7) composite resin only, 8) composite resin with GI cement. After develop the 3-dimensional model for finite element analysis, we observe the distribution of stress and temperature with force of 500N to apical direction at 3 point on occlusal surface and temperature of 55 degree, 15 degree on entire surface. The analyzed results were as follow : 1. Principal stress produced at the interface of base, dentin, cavity wall was smallest in case of using GI cement as base material under the amalgam. 2. Principal stress produced at the interface of base, dentin, cavity wall was smaller in case of using GI cement as a base material than ZPC under gold inlay. 3. Composite resin-filled tooth showed stress distributed over entire tooth structure. In other words, there was little concentration of stress. 4. ZOE was the most effective base material against hot stimuli under the amalgam and GI cement was the next. In case of gold inlay, GI cement was more effective than ZPC. 5. Composite resin has the small coefficient of thermal conductivity. So, composite resin filling is the most effective insulating material.

• Journal of Korean Society of Steel Construction
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• v.19 no.5
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• pp.473-482
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• 2007

When the material strength and ductility of shear studs is sufficient to carry the interface shear force, the composite beam can behave safely without premature structural failure in the interface and without ultimate moment reduction. In this study, the influence of the deformation capacity of shear studs embedded in high-strength concrete on structural behavior and design condition of composite beam is analyzed using FEM. In the analysis, load type, degree of shear connection and arrangement of studs are considered as analysis parameters. According to analysis results, in the case of partial interaction,the deformation capacity of studs embedded in high-strength concrete should be considered together with material strength. Especially in the case of uniform arrangement of studs and uniformly distributed load, a minimum available degree of shear connection is restricted by the deformation capacity of studs. In this case,shear studs should be arranged in consideration of the distribution of shear force at the composite section.