• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1993-1995
• /
• 2000

In this paper, we calculate the magnetic field and analyze the inductive interference in conductive material around power transmission line. To compute induced eddy currents as well as magnetic fields, finite element method(FEM) is used for numerical calculation. The characteristics, transmission line height, conductive earth and mitigation wire are taken account of FEM analysis. This research also shows that mitigation wire reduces amount of eddy current in buried pipe line.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.6 no.1
• /
• pp.23-28
• /
• 2010

The objective of this study is to develope ground heat exchanger using PHC pile used to building foundation, and it's element technology. So we made PHC piles into ground heat exchanger and evaluate it's performance. First, we studied PHC pile type, heat exchanger pipe, grouting materials, and present apartment house's foundation condition for PHC ground heat exchanger. As a result we designed BIGS(Building Integrated Geothermal System) prototype. Second, we applied BIGS to apartment houses' utility building in Osan built by Daelim. Third, we monitored heating performance of winter season. 1be result of heating performance was so good to apply to heat & cooling system in building.

• The Journal of the Acoustical Society of Korea
• /
• v.12 no.4
• /
• pp.21-31
• /
• 1993

불규칙한 기하구조 및 기하학적 특이점들을 갖는 방사체에 의해 형성되는 음장을 예측하는 작업은 매우 어려운 일이다. 이러한 종류의 문제를 해결하기 위하여는 Seybert에 의해 제창된 내, 외부를 연성하여 해석하는 경계요소법에 의한 해석이 유용하다고 여겨지고 있다. 본 연구에서는 연성경계요소법을 재 구성하여 예제로서 얇은 벽면을 갖는 개방된 관에서 방사되는 음장을 선택한 후, 이 방법의 신뢰성, 적용성 및 오차에 대한 해석을 해?ㄴ다. 외부 방사 문제에 있어서의 비유일성문제는 소외 CHIEF 기법을 도입하여 해결하였다. 두 개의 마이크로폰을 사용하여 신호처리를 통한 실험 결과와 본 경계요소법에 의한 결과는 서로 잘 일치하였다. 한편 경계면에 몹시 가까운 지점에서의 음장을 예측할 때의 오차 해석을 수행한 결과, 예측 오차가 10% 이내에서 유지되려면 경계요소법의 가장 짧은 변의 길이가 예측점과 벽면 사이의 거리보다 최소한 10배 이상은 커야함을 알아내었다. 이 기법은 기하학적인 특이점을 포함하는 각종 음향 문제에 매우 유효 적절한 방법으로 생각된다.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.381-386
• /
• 2006

The advantages of precast production are fast construction, reduction of labor and insurance of good quality. In recently, the application of the precast production is increased in the earth retaining wall field. This paper presents the results of the numerical modelling that was carried out to evaluate the stability of precast and prestressed earth retaining wall under dynamic train loading. The two-dimensional explicit dynamic finite element method (ABAQUS) was used to carry out the numerical analyses. The train loading to act track is calculated by using the real measured phase angle data. Mainly, the displacement and acceleration of wall structure in time domain analyzed to evaluate the stability under the dynamic train load.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.9 s.252
• /
• pp.1134-1141
• /
• 2006

This paper presents the model for evaluating restraint effect of pressure induced bending (PIB) on the circumferential through-wall crack opening displacement (COD), which considers plastic behavior of crack. This study performed three-dimensional elastic-plastic finite element (FE) analyses for different crack angle, restraint length, pipe geometry, stress level, and material conditions, and evaluated the influence of each parameter on the PIB restraint effect on COD. Based on these evaluations and additional perfectly-plastic FE analyses, a closed-form model to evaluate the restraint effect of PIB on the plastic crack opening of circumferential through-wall crack, was proposed as functions of crack angle, restraint length, radius to thickness ratio, axial stress corresponding to an internal pressure, and normalized COD evaluated from linear-elastic crack opening condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.21 no.7
• /
• pp.665-673
• /
• 2011

Simplified formulae for axial and bending natural frequencies of a bellows are developed using an equivalent thin-walled pipe model. The axial and bending stiffness of bellows is determined using lumped transfer matrix method. Transfer matrix method which includes the rotary inertia is used to calculate the natural frequencies for axial and lateral vibration. The result from the simplified formula are verified by those from as experiment result and a finite element analysis. This comparisons show good agreement with the each other.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.285-294
• /
• 1999

Transient analysis for compressible fluid flow has been performed experimentally and analytically to study the dynamic characteristics of the end volume transmission lines following a sudden pressure change a its entrance. The numerical method was developed based on the method of characteristics. The sudden pressure at its entrance was generated by rupture of diaphragm in a shock tube. The sudden pressure was used to obtain the response, as input signal for the numerical analysis. The response to the sudden pressure at the end volume was measured using a pressure transducer. The experimental result shows good agreements with the numerical result. The effects of tube length, its diameter and end volume magnitude are evaluated on the responses of the pressure and on the damping factor. It is found that the viscous damping effects on the response through the transmission pipeline becomes larger with increasing pi;eline length and decreasing diameter of the pipe and the fluid-elastic stiffness decreases with increasing the terminal volume. The numerical approach presented in this paper can be very useful in designing the instrument and control system.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.340-347
• /
• 1999

The acoustic performance of reactive type single expansion chamber can be calculated theoretically by plane wave theory. But higher order model should be considered to widen the frequency range. Mode matching method has been developed to consider higher order modes, but very complicated algebra should be used. Munjal suggested a numerical collocation method, which can overcome the shortcomings of mode matching method, using the compatibility conditions for acoustic pressure and particle velocity at the junctions of area discontinuities. But the restriction of Munjal's method is that the ratio between the area of inlet(or outlet) pipe and that of chamber must be natural number. In this paper, the new method was suggested to overcome the shortcomings of Munjal's method. The predictions by this method was also compared with those by the finite element method and Munjal's method in order to demonstrate the accuracy of the modified method presented here.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.5
• /
• pp.351-356
• /
• 2008

In this study, we had the stress analyses of TBP used in Tall Building and determined the working pressure of TBP. We knew the four fact. First, the place acted maximum stress is axial direction of branched part. Second, working pressure is more than 2.0 MPa. Third, stress in branched part is less than yielding strength at hydrostatic test pressure. Fourth, the ratio(stress/yielding stress at hydrostatic test pressure) is $0.4{\sim}0.6$(KS D 3562 Sch 40), $0.3{\sim}0.4$(KS D 3576 20S).

• International Journal of Korean Welding Society
• /
• v.2 no.2
• /
• pp.36-41
• /
• 2002

The experimental and numerical study has been conducted on the sleeve repair welding of API 5L X65 pipeline. SMAW and GTAW were applied to weld the sleeve. The macrostructure and hardness of repair welds have been examined. The finite element analysis of the multi-pass sleeve-fillet welding has been conducted to validate the experiment and investigate the effects of in-service welding conditions. The effect of gas flow rate on the hydrogen cracking was investigated. The effect of internal pressure on residual stresses and plastic strain was investigated. The allowable heat input was predicted considering the maximum temperature of inner surface of pipe and cooling rate at CGHAZ.