• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
• /
• pp.346-348
• /
• 2002

This paper analyze spectrum of vibration-frequencies to reduce noise level of distribution transformer. Using loading back method on same condition of a real load to grasp the effect of core and winding which are caused by the transformer vibration. we were measured the vibration-frequency by varing applied voltage and load current of a transformer. The major cause of a transformer vibration is occured by the harmonic effects, and was identified that the vibration is less influenced by the coil. As the result of this paper, comparing the transformer with some isolated material with the general transformer the transformer with some isolated material could reduce spectral amplitude of vibration-frequencies.

• 콘크리트학회논문집
• /
• 제11권4호
• /
• pp.129-136
• /
• 1999

For the prediction of concrete-steel bond ability in reinforced concrete, many countries establish specifications for the pullout test. But these methods hardly to consider many parameters such as strength, shape, diameter and location of steel, concrete restrict condition by loading plate, strength of concrete and cover depth etc, and it is difficult to solve concentration and disturbance of stress. The purpose of this study is to propose a New Ring Test method which can be rational quantity evaluations of bond splitting mechanism. For this purpose, pullout test was carried out to assess the effect of several variables on bond splitting properties between reinforcing bar and concrete. Key variables are concrete compressive strength, concrete cover, bar diameter and rib spacing. Failure mode was examined and maximum bond stress-slip relationships were presented to show the effect of above variables. As the result, it appropriately expressed general characteristics of bond splitting mechanism, and it proved capability for standard test method.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제12권1호
• /
• pp.325-342
• /
• 2020

The current study is focused on the evaluation of the ultimate strength of stiffened panels found in ship hull structures that are subjected to combined uniaxial thrust, in-plane and out-of-plane bending moments. This loading condition, which is in general ignored when performing buckling checks, applies to representative control geometries (stiffener with attached plating) as a consequence of the linearly varying normal stresses along the ship's depth induced by the hull-girder vertical bending moment. The problem is generalized by introducing a non-uniform thrust described by a displacement ratio and rotation angle and by introducing the slenderness ratios, within the practical range of interest. The formed design space is explored through methods sourcing from Design of Experiments and by applying non-linear finite element procedures. Surrogate empirical models have been constructed through regression analysis and Response Surface Methods. An additional empirical model is provided to the literature for predicting the ultimate strength under uniaxial thrust. The numerical experimentation has shown that is a significant influence on the ultimate strength of stiffened panels as the thrust non-uniformity increases.

• 한국재료학회지
• /
• 제32권4호
• /
• pp.223-229
• /
• 2022

A porous photocatalyst concrete filter was successfully produced to remove NOx, by mixing TiO₂ photocatalyst with lightweight aerated concrete. Ultra Fine Bubbles were used to form continuous pores inside the porous photocatalytic concrete filter, which was mixed via a bubble generation experiment. The optimal mixing condition was determined to be with 4 % of the bubble generation agent B. NO removal specimens were prepared for various photocatalytic loading conditions, and the specimen containing 3 % P-25 removed NO at a concentration of 1.03 µmol in 1 h. The NO removal rate of the porous photocatalytic concrete filter prepared in this study was 10.99 %. This photocatalytic filter performance was more than 9 times the amount of NO removed by a general photocatalytic filter. The porous photocatalyst concrete filter for removing NOx developed in this study can be applied to various construction sites and the air quality can be solved by reducing NOx contributing to the formation of fine particles.

• 한국지반공학회지:지반
• /
• 제14권2호
• /
• pp.55-66
• /
• 1998

본 논문의 목적은 불연속면의 공학적 특성, 사면형상과 하중조건 등을 고려한 암반사면 전도 파괴에 대한 안정해석방법을 개발하고 적용하는테 있다. 암반사면의 전도파괴에 대한 안정은 경사각 $\alpha_s$ 와 H/t비에 주된 영향을 받는다. 설계적용을 위하여 매개변수에 따른 My띠와 $\alpha$서 함수로 표현되는 암반사면 전도파괴에 대한 안정도표를 작성하였다. 안정도표에서 $\alpha_s$와 Hy띠가 작아질수록 안정성이 증가하는 경향을 보인다. 안정도표에서 안정영역은 간극수압변화에 따라 가장 크게 감소한다. 파괴영역의 변화는 지진력과 단계각에 가장 민감하다.

• 한국안전학회지
• /
• 제32권2호
• /
• pp.1-6
• /
• 2017

Modern society has been experiencing by population growth and urbanization that bring, a change of eating habits which has occurred a various types of waste in a large amount. Even though these wastes are required an immediate treatment with difficulties unsanitary handling and existing waste treatment method are by incineration, fermentation, drying and etc. however a bad smell occurs after the treatment that need's a lot of energy in processing organic wastes with high moisture contents and wasteful and inefficient problem. The strength assessment of the organic waste agitating vessel is required in terms of safety due to the differences of loading on the shaft that was treated by agitating the mixture of food waste. The damage of agitating axis is depended on steam pressure, temperature condition and the force moment that exerted by the food waste. Thus the strength assessment and stability evaluation are very important, especially to handle a hard waste. In this study the rotation capacity of agitation is about 5 tons considering general structural rolled steel pressure vessel strength and steam pressure. The purpose is to estimate the safety and strength evaluation for a agitator axis and impellers according to the rotating angle of the axis under the condition of the 3.2 ton capacity reactor.

• 한국항해항만학회지
• /
• 제43권5호
• /
• pp.310-319
• /
• 2019

With the recent increase in the volume of liquid cargo transportation, there is a need for STS( Ship To Ship) globally. In the case of the STS mooring, the safety assessment should be conducted according to other criteria because mooring is different from the general mooring at the quay, but there is no separate standard in Korea. Thus in this study, STS mooring simulation and sensitivity analysis using OPTIMOOR program, the numerical analysis program, was conducted to identify the characteristics of the STS mooring. The target sea modeled the Yeosu port anchorage in Korea and the target ship was selected as the case of VLCC (Very Large Crude Oil Carrier)-VLCC. Through the numerical simulation and sensitivity analysis, the characteristics of STS mooring were identified. Also based on these results, we focused on establishing the standard for STS mooring safety assessment. Numerical simulation results show that the STS mooring safety can be changed according to a ship's cargo loading condition, pre-tension of mooring line, sea depth, encounter angle with the weather, and the weather condition. Additionally, the risk matrix is prepared to establish the safe external force range in the corresponding sea area. This result can be used to understand the mooring characteristics of STS and contribute to the revision of mooring safety assessment criteria.

• 한국지반공학회지:지반
• /
• 제1권1호
• /
• pp.73-84
• /
• 1985

본 연구에거는 유한요소법에 의해서 제상하중을 받고 있는 연약지반의 응력분포와 변위를 규명하 였다. 응력에는 체적응력, 간극수압, 연직응력, 수평응력, 전단응력이 포함된다. 유한요소기법으로서 Christian-Boehmer방법을 택하였으며 진배수 및 비배수조건에서 일반탄성model과 참정 Cam-clay model을 지배방정으로 선정하였다. 그 결과는 다음과 같다. 1. 체적응력은 간극수압과 거의 일치한다. 이는 비배수조건에서 전응력이 간극수탄과 같다는 것 을 의미한다. 2. 연직응력은 배수 및 비배수표건이라 구성식의 model에 관계없이 같은 갈을 나타런다. 3. 수평응력은 배수조건과는 무관하지만 구함식의 model에 따라서 다른 값으로 나타난다. 4. 전단응력은 배수조건 및 구성식의 model model에 따라 다른 값이 된다. 수정 Cam-clay에 의한 해석치가 가장 크게 된다. 5. 변위 Vector의 방향은 하중이 증가하는 동안 성토법면근방에서 외향으로 향한다. 6. 변위의 크기는 수정 Cam-clay에 의한 해석이 탄성 model의 2배가 된다.

• 한국전산구조공학회논문집
• /
• 제21권1호
• /
• pp.35-42
• /
• 2008

원자력발전소에서는 열교환 파이프에서 발생하는 열피로 균열을 비파괴 탐상장비를 이용하여 조기에 발견하는 것이 안전을 위해 매우 필요하며, 따라서 이를 모사한 인공균열시편 제작에 많은 노력을 기울이고 있다. 그러나 이러한 균열은 일반 기계가공으로 제작하는 것이 불가능하여 실제 조건과 유사한 열 반복하중 하에서 제작될 수밖에 없는데, 이를 위해 많은 시간이 소요된다. 본 연구에서는 크랙성장 시뮬레이션 기법을 이용하여 이러한 균열 제작시간을 단축하기 위한 최적의 열하중 조건을 찾고자 하였다. 이를 위해 임의조건에서 시뮬레이션 및 열피로균열 발생 기초실험을 수행하여 균열 초기수명과 진전수명을 검증하였고, 이를 바탕으로 다양한 가열 및 냉각시간을 시뮬레이션 함으로써 제작시간을 최소화하는 열하중 조건을 구하였다. 시뮬레이션에서는 응력해석을 위해 상용 소프트웨어 ANSYS를 초기균열수명 계산을 위해 수치계산용 소프트웨어 ZENCRACK을 이용하여 코딩을 균열진전수명 평가를 위해 ZENCRACK 소프트웨어를 이용하였다. 그 결과 1mm 균열 제작에 소요되는 시간은 초기의 418시간에서 319시간으로 24% 단축되는 것으로 예측되었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1115-1120
• /
• 2003

The recent tendency in the automobile industries is toward light weighting vehicle body to improve the problems by environmental pollution as well as improving fuel cost. The effective way to reduce the weight of vehicle body seems to be application of new materials for body structure and such trend is remarkable. Among the various materials for vehicle body, stainless steel sheet (for example, 301L and 304L), TRIP steel and cold rolled steel sheets are under the interests. However, in order to guarantee reliability of new material and to establish the long life design criteria of body structure, it is important and require condition to assess spot weldability of them and fatigue strength of spot welded lap joints which were fabricated under optimized spot welding condition. And, recently, a new issue in the design of the spot welded structure is to predict economically fatigue design criterion without additional fatigue tests. In general, for fatigue design of the spot-welded thin sheet structure, additional fatigue tests according to the welding condition, material, joint type, and fatigue loading condition are generally required. This indicates that much cost and time for it should be consumed. Therefore, in this paper, the maximum stresses at nugget edge of spot weld were calculated through nonlinear finite element analysis first. And next, obtained the ${\Delta}P-N_{f}$ relation through the actual fatigue tests on spot welded lap joints of similar and dissimilar high strength steel sheets. And then, the ${\Delta}P-N_{f}$ relation was rearranged in the ${\Delta}{\sigma}-N_{f}$ relation. From this ${\Delta}{\sigma}-N_{f}$ relation, developed the fatigue design technology for spot welded lap joints of them welded using the optimized welding conditions.