• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.60-66
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• 2005

Corrosion highly affects the lifetime and performance of machinery metallic components. The effects of shot peening on the fatigue life of Al 7075-T6 under corrosive environment are investigated in this paper. Experimental results show that the fatigue limit of shot peened specimen increases about 52%. That means the fatigue life of metallic components is highly extended by shot peening. The corrosion greatly reduces the fatigue strength depending on the corrosive condition from one week up to one year. In case of shot peened specimen, the corrosion does not reduce the fatigue strength and fatigue life up to six months. It means that the shot peening has superior effectiveness to reduce the influence of corrosion to the metallic materials.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.809-817
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• 2008

Recently, the external prestressing method is being much frequently used in strengthening reinforced concrete structures because of it's excellent load resistance and serviceability increases comparing to other strengthening methods. However, it is true that the research on fatigue performance of concrete structures strengthened by the external prestressing using FRP tendons is rare. Therefore, the purpose of this study is to evaluate the safety and feasibility of the external prestressing method by analyzing the characteristics of the reinforced concrete beam strengthening using FRP tendons under repeated loads. Test variables adopted in this experimental study are the types of external prestressing material (steel or FRP tendon) and the repeated load ranges. The repeated load range have the minimum 50% of yield load of reinforced concrete beam and the maximum 70-85%. The test beams are loaded by 4 point loadings with 3 Hz sine wave. From this experimental study, it is confirmed that the reinforced concrete beams strengthened using FRP tendons have sufficient safety against fatigue, especially in FRP tendon itself, tendon at deviators and tendon at anchorages.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.1-7
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• 2023

Durability was evaluated by performing a full-scale vertical load fatigue test and a wheel load performance test on the HRS, which reduces the replacement time of the existing expansion joint and improves serviceability to allow partial replacement by lane. As a result of the vertical load fatigue test, the maximum stress of the rail-type expansion joint is 170 MPa, which is about 47.8% of the yield strength of the HRS expansion joint rail 355 MPa. The vertical load fatigue test of the HRS expansion joint with improved serviceability set the size and load of the load plate according to the road bridge design standards, did not show any fracture behavior in the vertical load fatigue test and the wheel load performance test 2 million times, and its durability and safety were verified.

• Computational Structural Engineering
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• v.22 no.2
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• pp.61-65
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• 2009

• 전기의세계
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• v.13 no.2
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• pp.56-58
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• 1964

본고에서는 선형연산기의 성능은 이미 보고된바 있으므로 재론을 피하고 설계에 있어서 유의한 점 몇가지를 들고, 이 계산기의 주요 구성요소와 간단한 실험결과를 보고하기로 한다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.3-4
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• 2009

This study predicts the structural behavior of RC beams using high strength shear reinforcement and evaluates current design codes restricting the strength of shear reinforcement steel. Under the present design codes, the yield strength of shear reinforcement steel is restricted to 400MPa. In case that use high yield strength reinforcement steel, could incure heavily crack and deflection at the members of structure, and have not verified ductility capacity, fatigue resisting capacity, shear and torsion resisting capacity, anchoring capacity and seismic capacity. To this end, we evaluate structural behavior of reinforced concrete beams using high strength shear reinforcement.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.135-144
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• 2011

Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam's safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam's static strength, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1297-1307
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• 2009

The purpose of this paper is to propose a detection algorithm and a tracking algorithm based on silent time using MB-OFDM UWB(Multi-Band Orthogonal Frequency Division Multiplexing Ultra Wide Band) receiver in order to satisfy DAA(Detect And Avoid) regulation of Korea to permit UWB in 3.1~4.8 GHz. In DAA regulation of Korea, if UWB device receives a signal more than -80 dBm/MHz from the victim system during UWB operation, the UWB system should avoid the collision within 2 sec. In this paper, we proposed the detection algorithm to detect the victim signal received by －80 dBm/MHz for the avoidance process that changes the operating UWB frequency to other UWB frequency and the subcarrier tracking algorithm to follow up the subcarrier positions of the victim signal for the tonenulling avoidance process that decreases the TX power of subcarriers occupied by the victim signal by -70 dBm/MHz. The performance of the detection algorithm and the tracking algorithm suggested in this paper is verified in simulation results considering various conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1027-1035
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• 2016

In this study, a strain-controlled fatigue test of widely-used 316L stainless steel with excellent corrosion resistance and mechanical properties was conducted, in order to assess its fatigue life. Low cycle fatigue behaviors were analyzed at room temperature, as a function of the strain amplitude and strain ratio. The material was hardened during the initial few cycles, and then was softened during the long post period, until failure occurred. The fatigue life decreased with increasing strain amplitude. Masing behavior in the hysteresis loop was shown under the low strain amplitude, whereas the high strain amplitude caused non-Masing behavior and reduced the mean stress. Low cycle fatigue life prediction based on the cyclic plastic energy dissipation theory, considering Masing and non-Masing effects, showed a good correlation with the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.209-216
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• 2005

The objective of this paper is to investigate the H & Channel type lining board's capacity by using the fatigue test. The accumulated test result will be used to analyze the relation between the cause of crack occurrence and the behavior of structure. H type lining boards was comfortable behaved in over one million recycled. loading test. In case of channel type lining board specimens occurred the fatigue fracture in about one hundred thousand recycled loading test, and then could not secured endurance life that used servicing load.