• 한국해안·해양공학회논문집
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• 제27권1호
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• pp.14-24
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• 2015

본 연구는 선박의 크기, 계류조건, 파랑의 주기, 파향 등에 의한 계류선박의 동요량을 해석하고 선박의 하역한계파고 산정 및 항만가동율을 평가하는 방법을 제시한 것이다. 본 방법은 포항신항 제8부두의 파랑관측자료를 이용하여 타당성을 검증하였다. 하역중단 시 파랑관측 자료는 파고 0.10~0.75 m, 주기 7~13 s 이었으며, 이때 계류된 선박은 800~35,000톤 이었다. 그리고 본 방법으로부터 산정된 제 8부두의 하역한계파고는 선박 5,000, 10,000, 30,000톤에 대하여 파고 0.19~0.50 m, 주기 8~12 s로 산정되었다. 본 방법의 결과는 연구대상 선박의 크기가 현지 선박의 크기와 정확히 일치하지는 않아서 파고는 관측치와 다소 차이를 보이지만 주기변화에 따라 하역한계파고를 잘 재현하고 있음을 알 수 있었다. 그리고 파향이 75도 인 경우의 본 방법에 의한 하역한계파고는 현행 항만설계 기준에 제시된 한계파고 보다 장단주기 파를 고려하면 16~62% 감소하였고, 단주기 파랑만 고려하면 0~46%감소하였다. 특히 현행 항만설계기준의 하역한계하고는 10,000톤 이하의 선박에 대해서는 과대 평가되었음을 확인할 수 있었다. 한편, 선박의 동요량을 고려하여 산정된 포항신항 제 8부두의 가동율은 설계기준 파고에 의한 가동율 에 비하여 6.5% 감소하였다.

• 한국지반공학회논문집
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• 제20권8호
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• pp.49-58
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• 2004

콘프레셔미터는 피에조콘 시험과 프레셔미터 시험을 동시에 수행할 수 있는 현장시험기로서 본 연구에서는 국내 점토지반에서 수행한 시험결과를 해석적으로 분석하였다. 콘프레셔미터 결과에 대한 이론적인 해는 흙이 비선형 거동을 하는 경우와 전단변형 중 체적변화가 발생하지 않는 경우에 대하여 해석적인 해가 존재한다. 이러한 해석적인 해로부터 콘프레셔미터의 결과중 하중 재하구간과 제하구간에 대해 Curve Fitting 방법을 사용한 콘프레셔미터 결과의 해석 방법을 제안하였다. 20개소의 현장에서 수행한 콘프레셔미터 결과 중 지반교란의 영향을 적게 받는 제하구간에 대하여 Curve Fitting 방법을 적용하여 점성토의 비배수 전단특성을 구하였다. 이렇게 구한 지반의 비배수 전단강도와 현장 Vane, 일축압축, 삼축압축 시험결과로부터 구한 지반의 비배수 전단강도를 서로 비교하여 콘프레셔미터 시험 결과로부터 Curve Fitting 방법을 통한 점성토 지반의 전단강도 특성파악의 적정성에 대해 평가하였다.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.105-113
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• 2018

To improve the prediction accuracy of the strong-unloading rock slope performance and obtain the range of variation in the slope displacement, a new displacement time-series prediction model is proposed, called the fuzzy information granulation (FIG)-genetic algorithm (GA)-back propagation neural network (BPNN) model. Initially, a displacement time series is selected as the training samples of the prediction model on the basis of an analysis of the causes of the change in the slope behavior. Then, FIG is executed to partition the series and obtain the characteristic parameters of every partition. Furthermore, the later characteristic parameters are predicted by inputting the earlier characteristic parameters into the GA-BPNN model, where a GA is used to optimize the initial weights and thresholds of the BPNN; in the process, the numbers of input layer nodes, hidden layer nodes, and output layer nodes are determined by a trial method. Finally, the prediction model is evaluated by comparing the measured and predicted values. The model is applied to predict the displacement time series of a strong-unloading rock slope in a hydropower station. The engineering case shows that the FIG-GA-BPNN model can obtain more accurate predicted results and has high engineering application value.

• 한국해양공학회지
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• 제15권3호
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• pp.75-80
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• 2001

The elastic plastic fracture toughness of this material is evaluated by the an unloading compliance method according to the ASTM E813-97 and E1152-97 method on the smooth and side groove 1CT specimens. The effect of smooth and side groove is studied on the material tearing modulus and characterizes the crack tip field under the plane stress and strain. SG-365 steel is observed that J-R curve and Tmat value decrease as 0%, 20%, 30%, and 40%. The 40% side grooved specimen is very useful in estimation of the $J_IC$. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides. it improves the accuracy of toughness values, decreases the scattering the them and tunneling and shear lip by the side groove. Applicability of tearing modulus($T_J$ proposed by paris et al as instability panameter for this material is investigated.

• 대한기계학회논문집A
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• 제22권2호
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• pp.343-351
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• 1998

This paper was investigated degradation of the fracture toughness caused by sensitizing heat-treatment of the cryogenic structural material JN1 base metal using unloading compliance method reported as useful a method in evaluating the elastic-plastic fracture toughness at cryogenic temperature. The specimens used in this paper were 20% side-grooved 0.5T-CT specimens which were machined in the JN1 base metal. Also, to investigate cryogenic fracture toughness of the fusion line region in the JN1 GTA weldments, it was also used 20% side-grooved 0.5T-CT specimens that was machined fusion line to located in the middle of the specimen. The cryogenic fracture toughness values of the JN1 base metal were significantly decreased with increasing the time and temperature of the heat treatment. The fracture toughness value obtained from the fusion line specimen was invalid, but it was lower value than that of the JN1 base metal. Especially, this value was approximately equal with that obtained from the JN1 650.deg. C-5h heat-treated material.

• 한국정밀공학회지
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• 제22권10호
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• pp.186-194
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• 2005

This study was designed to investigate the mechanical properties of the coating layer on electronic galvanized sheet steel as a part of the ongoing research on the coated steel. Those properties were determined using nano-indentation, the finite element method, and artificial neural networks. First and foremost, the load-displacement curve (the loading-unloading curve) of coatings was derived from a nano-indentation test by CSM (continuous stiffness measurement) and was used to measure the elastic modulus and hardness of the coating layer. The properties derived were applied in FE simulations of a nano-indentation test, and the analytical results were compared with the experimental result. A numerical model for FE simulations was established for the coating layer and the substrate separately. Finally, to determine the mechanical properties of the coating, such as the stress-strain curve, functional equations of loading and unloading curves were introduced and computed using the neural networks method. The results show errors within $5\%$ in comparison with the load-displacement measured by a nano-indentation test.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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• pp.228-231
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• 2001

Elastic-plastic fracture toughness $J_{1c}$ can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are operated at high temperature and $J_{1c}$ values are affected by temperature. therefore, the $J_{1c}$ valuse at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness $J_{1c}$ tests were performed on SA516 carbon steel plate and test results were analyzed according to ASTM E 813-8, ASTM 1813-89. Safety and integrity are required for reactor pressure vessels vecause pthey are operated in high temperature. there are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness$(J_{1c})$ and $J-\Delta{a}$ of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room Temperature, $150^{\circ}C$, $250^{\circ}C$ and $370^{\circ}C$ according to unloading compliance method.

• 정보저장시스템학회논문집
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• 제2권3호
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• pp.169-177
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• 2006

In this study, we present the optimization of a head slider using kriging method in order to reduce lift-off force during unloading process with satisfying reliable flying attitude in steady state. To perform an optimization process efficiently, a simplified lift-off force model, which is a function of air bearing suction force and flying attitudes, is created by kriging method. The EMDIOS, which is the process integration and design optimization software developed by iDOT, is used to automatically wrap the analysis with the optimization and efficiently implements the repetitive works between analyzer and optimizer. An optimization problem is formulated to reduce the lift-off force during unloading process while satisfying the flying attitude in reliable range over the entire recording band and reducing the probability of contact between slider and disk. The simulation result shows that the amplitude of lift-off force of optimized L/UL slider is reduced about 62%, compared with that of initial slider model. It is demonstrated by the dynamics L/UL simulation that the optimum slider incorporated with the suspension is not only smoothly loaded onto disk but also properly unloaded onto the ramp.

• 한국해양공학회지
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• 제15권2호
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• pp.99-104
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• 2001

Elastic-plastic fracture toughness $J_{lc}$ can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are$J_{lc}$ $J_{lc}$ value at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness $J_{lc}$ tests were performed on SA516/70 carbon steel plate and test results were analyzed according to ASTM E 813-87, ASTM E 813-89 and ASTM E 1152-87.safety and integrity are required for reactor pressure vessels because, they are operated in high temperature. There are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness($J_{lc}$) and J-$\Delta$a of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room temperature, 150$^{\circ}C $, 250$^{\circ}C $ and 370$^{\circ}C $ according to unloading compliance method.

• 한국소음진동공학회논문집
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• 제22권3호
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• pp.244-252
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• 2012

Recently, the speed of a train has been increased. So the trains are being exposed to wind more severely than before. Because of the operation of high speed trains and lightweight of the train, risks of train derailment have being increased. In this study, aerodynamic effects of a newly designed high speed train, HEMU-400x, are evaluated. For aerodynamic effect evaluation, analysis method is selected by examining the safety standards for high speed train. The condition of aerodynamic effects is selected by adverse effect conditions. In order to calculate $C_s$ coefficients, numerical analysis is conducted. Using $C_s$ coefficients, the side force is calculated. Through dynamics analysis, derailment and wheel unloading are obtained. Using these results, derailment evaluation is performed.