• Ocean Systems Engineering
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• 제6권4호
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• pp.325-344
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• 2016

Using 3D computational fluid dynamics techniques in recent years have shed significant light on the Vortex Induced Vibrations (VIV) encountered by deep-water marine risers. The fatigue damage accumulated due to these vibrations has posed a great concern to the offshore industry. This paper aims to present an algorithm to predict the crossflow and inline fatigue damage for very long (L/D > $10^3$) marine risers using a Finite-Analytical Navier-Stokes (FANS) technique coupled with a tensioned beam motion solver and rainflow counting fatigue module. Large Eddy Simulation (LES) method has been used to simulate the turbulence in the flow. An overset grid system is employed to mesh the riser geometry and the wake field around the riser. Risers from NDP (2003) and Miami (2006) experiments are used for simulation with uniform, linearly sheared and non-uniform (non-linearly sheared) current profiles. The simulation results including inline and crossflow motion, modal decomposition, spectral densities and fatigue damage rate are compared to the experimental data and useful conclusions are drawn.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.75-75
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• 2004

Carbon/epoxy는 기존의 금속재료에 비해 피로강도 및 기계적 특성이 매우 우수하다. 따라서 최근 튜브형태의 Carbon/epoxy 활용방안이 부각되고 있다. 그러나 Carbon/epoxy는 탄소재료의 특성상 고압, 충격 및 부식에 매우 취약하다. 또한, 장기간 고압피로 및 크리프에 노출될 경우, 금속재료에서는 관찰할 수 없는 층간분리(delamination)가 발생된다. 이러한 층간분리는 섬유방향과 평행하게 진전될 때 급격한 파손을 야기하므로 층간분리에 대한 메커니즘을 이해하고 그 방지책을 강구하는 것은 매우 중요하다.(중략)

• Journal of Magnetics
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• 제18권2호
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• pp.90-94
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• 2013

We designed a model composed of a ring type magnet, a yoke, and a sensing coil embedded in a projectile for simulating the muzzle velocity. The muzzle velocity was obtained from the master curve for the induced voltage at sensing coil and the velocity as the projectile pass through the magnetic field. The induced voltage and the projectile's velocity are fitted by the $2^{nd}$ order polynomial. The skin effect difference between projectiles which consist of aluminum-aluminum and aluminum-steel was small. The projectile will surely be burst at the pre-determined target area using the flight time and the projectile muzzle velocity calculated from the voltage induced at the sensing coil on the projectile.

• Nuclear Engineering and Technology
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• 제30권4호
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• pp.377-385
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• 1998

Many nuclear power plants have experienced unscheduled shutdown due to the leakage of steam generator tubes. The leakages are normally due to the crack, possibly stress corrosion cracking (SCC) near the tube expansion at the top of tubesheet or at the tangential point of the row-1 U-bend region. The conventional eddy current technique, which makes use of a differential bobbin coil, has been found to be inadequate for the early detection of SCC. During the in-service inspection, therefore, it is a general practice that the rotating pancake coil (RPC) is used for detecting the cracks. Even in using RPC, however, it is difficult to determine the depth of the cracks quantitatively. This paper attempts to determine the detectability and sizing ability of RPC technique for axial or circumferential cracks at the tube expansion region. The simulated cracks with various dimensions were fabricated by electro-discharge machining (EDM) method. Experimental results are discussed with theoretical calculations.

• 한국자기학회지
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• 제7권4호
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• pp.212-216
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• 1997

충전에너지 18 kJ의 커패시터뱅크 및 펄스코일에서 생성되는 주기 10.12 ms의 정현감쇄진동형 펄스자장을 이용하여 최대 인가자장 130 kOe의 펄스마그네토미터를 구성하였다. 자성측정은 펄스자장의 첫 번째와 두 번째 정방향 자장파크 사이의 파형을 이용하여 유도법으로 측정하였다. NdFeB 소결자석의 측정에 있어서 와전류에 의한 측정오차, 즉, 직류특성과의 차이가 직경 5 mm 이하의 시편을 사용할 경우 3% 이내인 펄스자장형 자기이력곡선 측정장치를 제작하였다.

• Journal of Magnetics
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• 제16권2호
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• pp.88-91
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• 2011

Steam generator tubes (SGTs) in nuclear power plants (NPPs) are a boundary between the primary side generating heat by nuclear fission and the secondary side generating electric power by a turbine. The water inside the SGT is high temperature and high pressure. Therefore, defects and magnetic phases (MPs) are partly produced in non-magnetic SGT by high stresses and temperatures. This causes trouble regarding the safety of SGTs but it is difficult to detect the MP using the conventional eddy current technique (ECT). In particular, a circumferential defect (CD) and circumferential magnetic phase (CMP) cannot detected by ECT. Consequently, a new method is needed to detect CDs and CMPs in SGT. A new U-type yoke with two types of coils was designed and the reactance signal by the CMPs and CDs in the SGT material was simulated.

• 한국압력기기공학회 논문집
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• 제6권2호
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• pp.9-15
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• 2010

US NRC issued rulemaking of 10CFR50.55a to perform the Perservice and Inservice inspection for Reactor Vessel Head Penetration Nozzle of US Nuclaer plant. The rulemaking was required the EPRI Demonstration to verify the NDE technique performing special Ultrasonic examination. In order to meet this requirement, the UT and ECT procedures was demonstrated and the NDE personnel were qualified by EPRI. In this paper, the NDE technique and analysis method are described the Preservice inspection for the Palo Verde #1/2/3 Replacement Reactor Vessel Head Penetration Nozzle using the qualified procedures and personnel.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.54-60
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• 2014

This paper shows a calculation method of several types of loss and the efficiency of brushless DC motors coupled with a load system by using a simple equivalent circuit, in which copper loss, eddy current loss, hysteresis loss, friction loss, viscous loss, and inverter loss are taken into account. We clarify each loss and motor efficiency at different motor speeds and different output torques by using the Microsoft-Excel. Moreover, the calculated results are in good agreement with the measured ones.

• 전기학회논문지
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• 제65권5호
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• pp.777-784
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• 2016

In this paper, the performance design and analysis for an Interior Permanent-Magnet Synchronous Motor (IPMSM) that will be used as a traction motor in the e-4WD system of hybrid SUV(Sports Utility Vehicle) and RV(Recreational Vehicle), are investigated using finite element method. In order to improve the accuracy of design, the tolerances of parts and assemblies as well as the material properties of permanent magnet, stator, rotor and winding etc. are considered under the conditions similar to real driving state of motor. Both no load performance test and maximum load performance test, in which real driving state and cooling condition have been considered, are also implemented via proto sample build to verify the validity of motor's performance design.

• 한국전기전자재료학회논문지
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• 제29권1호
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• pp.58-61
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• 2016

Degradation in power cables used in distribution lines to the material of the wire, manufacturing method, but also the line of the environment, generates a variety of degradation depending upon the type of load. The local wire deterioration weighted wire breakage accident can occur frequently, causing significant proprietary damage can lead to accidents and precious. In this study, the signal detected by the eddy current aim to develop algorithms capable of determining the signals for the top part and at least part of the signal by using a signal processing technique called K-means algorithm.