• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1576-1582
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• 1990

To examine small fatigue crack behavior, the crack opening displacement (COD) was measured for surface cracks in the range of few tens to hundreds .mu.m using the computerized Interferometric Strain/Displacement Gage (ISDG) which could measure the relative displacement with a resolution of 0.02 .mu.m. The load-COD record is stored and analyzed after the test to determined the opening load. Single-edge notched specimens, 2.3mm thick, of Al 2024-T3 were precracked at load ratios of 0.0, -1.0 and -2.0 to make small fatigue cracks. The opening loads were measured these small cracks and compared with those of long cracks. The opening load ratios for the short cracks are about 10% smaller than those for long cracks at positive R-ratios, but are about 100% smaller at negative R-ratios.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.1
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• pp.69-75
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• 2010

A model ship equipped with the Weis-Fogh type ship's propulsion mechanism, which is consisted of one wing in a squared channel, was constructed. Sailing and vibration tests of the model ship were performed with the opening angles in a pool. The results are summarized as follows. The thrust and the speed of model ship were the highest for the spring-type wing of which the opening angle is automatically controlled in one stroke. Moreover, these values were approximately reduced by 4% from $30^{\circ}$ opening angle to $15^{\circ}$ in order. The maximum amplitude and RMS values of the model ship were the lowest for the wing having the opening angle of $30^{\circ}$, but were the largest for spring-type wing. And in case of the same opening angle, these values were lower for the ship on sailing than that on stationary.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.6
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• pp.35-41
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• 2007

The rate of loading in motor operated valve(MOV) can be defined as a variation of correlation between the actuator torque and the thrust upon the variation of operating load. This paper contains the analysis of characteristic and the validity of loading rate in the opening stroke of gate type motor operated valve. Also, this paper describes the evaluation result of loading rate for 40 MOVs' opening stroke using newly derived methodology in this study. Author has found a result that loading rate of opening stroke gets a negative value when the differential pressure is higher than 150 psi and this value goes up depending on the amount of the differential pressure.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.395-397
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• 2000

본 논문에서는 Grafcet을 이용하여 고속 철도의 외부 승강문 운영 데이터 처리 사양으로부터 승강문 운영 상세 사양을 구성하는데 목적을 둔다. 이에 따라 승강문 열림/닫힘, 승강문 열림 및 승강문 닫힘 관련 Grafcet을 구성한 후, 천이와 스텝의 관점에 따라 연관된 액션과 천이 조건 등을 분류하여 주어진 Grafcet의 특성 및 순차 제어 논리 분석을 실행한다.

• The KSFM Journal of Fluid Machinery
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• v.8 no.6 s.33
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• pp.15-25
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• 2005

Check valves playa vital role in the operation and protection of nuclear power plants. Check valves failure in nuclear power plants often lead to a plant transient or trip. The analysis of historical failure data gives information on the populations of various types of check valves, the systems they are installed in, failure modes, effects, methods of detection, and the mechanisms of the failures. A majority of check valve failures are caused by improper application. The experimental apparatus is designed and installed to measure the disc positions with flow velocity, Vopen and Vmin for 3 inch and 6 inch swing check valves. The minimum flow velocity necessary to just open the disc at a full open position is referred to as Vopen, and Vmin is defined as the minimum velocity to fully open the disc and hold it without motion. In the experiments, Vmin is determined as the minimum flow velocity at which the back stop load begins to increase after the disc is fully opened or the oscillation level of disc is reduced below $1^{\circ}$. The results show that the Vmin velocities for 3 inch and 6 inch swing check valves are about 27.3% and 17.5% higher than the Vopen velocities, respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.2
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• pp.155-169
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• 2002

The objective of this study was to investigate the effect of crack opening and closure in the AE activities during fatigue test. Laboratory experiment using various materials and test conditions were carried out to identify AE characteristics of fatigue crack propagation. Compact tension specimens of 2024-T4 and 6061-T6 aluminum alloy were prepared for fatigue test. AE activities were analyzed based on the phase of the loading cycle. Generally, most of AE were generated when the crack begins' opening and the crack closes fully, whereas a few in the pull opening of the crack. Also AE activity in the peak loading of cycle was different with each specimen. However, in the same material, AE activity was not affected by the change of cyclic frequency (0.1, 0.2, 1.0Hz). It was found that AE activities during crack opening and closure depend on material properties such as micro-structure, tensile strength and yield strength.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.45-52
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• 2010

A model of the propulsion mechanism, I, II, III was based on a two-dimensional model of the Weis-Fogh mechanism and consisted of one or two wings in a square channel. The sailing and vibration performance characteristics of model ships were tested to compare with each other. we took results as follow. Thrust of propulsion model, I and III was increased by 31% and 43%, the speed of model ship by 20% and 23%, When compared to model II in same condition. The thrust improvement using the elastic spring wing was effective not only on all models but also in the real ship. The maximum amplitude and RMS were largest at the opening angle ${\alpha}=15^{\circ}$ and smallest at ${\alpha}=30^{\circ}$ on the vibration of model ship. The thrust of propulsion model III with opening angle ${\alpha}=30^{\circ}$, phase ${\Delta}T=0^{\circ}$ was large, but the amplitude of vibration was small relatively.

• Fire Science and Engineering
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• v.16 no.4
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• pp.59-64
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• 2002

Investigation of flow characteristics on pressure loss and cavitations of the butterfly valve has been carried out. The pressure loss coefficient on opening angle of valve has been formulated by applying the Carnot's equations. Cavitations (such as cavitation Inception, super cavitation inception, cavitation damage inception, choking cavitation) have been predicted from the pressure loss coefficient of valve. The prediction of pressure loss and cavitation has been carried out change of the thickness ratio on opening angle of valve. The prediction data is utilize to necessary engineering data to develope of the butterfly valve.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.289-298
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• 2000

In order to minimize the impact of water hammer In a pipeline, a determination of optimum position of hydraulic structures with best operation of pressure relief valve was explored at the Seobyun pumping station. Method of characteristics is used to simulate a surge impact originating from abrupt stop of pumping operation in a pipeline. Genetic algorithm shows a powerful capability in searching a global solution, especially for a nonlinear problem The application results suggests that the maximum positive pressure can be relaxed by decreasing the opening time of pressure relief valve, meanwhile the maximum negative pressure can be relaxed by increasing the opening time of pressure relief valve. This study shows that the integration of a genetic algorithm with a transient analysis technique such as method of characteristic can improve the design of hydraulic structure in a pipe network.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.96-102
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• 1990

Cracks found in pressure vessels have been reported to be mostly semi-elliptic surface cracks. The fatigue crack growth behaviour of the surface cracks on pressure vessel materials, SPV 50Q and API 5A-K55, was studied with the consideration of the crack opening character. To determine the crack opening loads for the surface cracks, the displacement/strain were measured at three positions; the center and the side of the surface crack, the back face of the specimen using CMOD gauge and strain gauges. The experimental results showed that the crack opening load levels measured at the side of the surface crack were generally a little higher than those measured at the back face. As for the crack growth rates at the different parts of the surface crack, the experiments also showed that, if .DELTA.K$_{eff}$ is used, the exponent n of the Paris' law obtained were the same for the rear and the side parts of the surface cracks.