• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.4
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• pp.1-11
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• 1980

Stiffened plates are commonly used as a component of ship's structures. Most frequently symmetrically stiffened plates are used, but some of stern structures and any specified parts are often constructed with eccentrically stiffened plates. The problems of these eccentrically stiffened plates have been studied rarely, and the results of eccentricity effect of eccentrically stiffened plates are not available. This paper deals with the analysis of eccentrically stiffened plates in the linear elastic range. The derivation of the stiffness matrix was carried out by finite element method for which the isoparametric element was adopted. To show the effect of eccentricity, the deflection at the center under the uniformly distributed and the concentrated load of simply supported and clamped plate models are computed respectively in accordance with the eccentricity of the stiffener. As shown in the results of computations, the eccentricity effect of concentrated load case is greater than that of distributed load case and that of simply supported boundary condition is greater than that of clamped boundary condition. The higher eccentricity of stiffener is, the smaller the effect of stiffener becomes, therefore scantling of eccentrically stiffened plates should be considerably greater than those of symmetrically stiffened plates.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.2
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• pp.106-113
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• 2004

The block assembly of ship consists of a certain type of heat processes such as cutting, bending, welding, residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. Systematic and quantitative theoretical works to clarify the effects of various factors on the welding deformation have rarely been found. Therefore, in this paper, the effects of various factors, such as welding process and gravity on the butt welding deformation have been investigated through a number of numerical analyses. In addition, this paper proposes a simplified analysis method to predict the butt welding deformation in actual plate structure. For this purpose, a simple prediction model for butt welding deformations has been derived based on numerical and experimental results through the regression analysis. Based on these results, the simplified analysis method has been applied to some examples to show its validity.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.87-92
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• 2013

The variation in the course keeping ability in relation to rudder type is investigated using simulations with 3 different types of rudders (a normal rudder, normal rudder with a plate, and Schilling rudder) under wave conditions. The simulation is developed based on an MMG model with Kijima's regression model, along with the data from Son's experiments and Kose's experiments. A 3-D source distribution method is applied to calculate the source of the external wave forces for the simulation. The coefficients of an autopilot controller that may affect the course keeping ability are also estimated from the simulations with the different rudders. The course keeping ability is evaluated by comparing the forward distances while the ships are simulated with the rudders and autopilot controller.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.468-473
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• 2016

This paper focuses on the estimation of local ice loads exerted from ship-ice interaction processes. The Korean IBRV ARAON was used to perform field ice trials during her 2015 Arctic voyage. During ARAON's general ice transit, a total of 72 channels of data from both strain gauges on the inner hull plates and those installed on the transverse frames of the ARAON's bow section structures were analyzed to calculate the local ice loads. The local ice loads estimated from the analysis of the shear strain data measured on the side frames were compared to those from the hull plate pressures.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.275-284
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• 1991

Fatigure crack growth from surface defects is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, ship hulls and other various structures. This paper attempts to analysis some practical or general problems such as the estimation of crack growth life to penetrate the plate thickness, based on fatigure crack growth from a single surface flaw and the interaction of multiple flaws. An experiment on the coalescence of multiple undercuts was carried out under cyclic tension condition as a attempt to the analysis of multiple crack problems. It is noted that the fracture strength is characterized by the analogy to that in a single crack growth.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.6
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• pp.695-702
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• 2008

In this paper, a new numerical method is proposed to analyze near-field sonar cross section of acoustically large-sized underwater targets such as submarines. A near-field problem is converted to a far-field problem using a spherical projection method with respect to the objective target. Then, sonar cross section is calculated with a physical optics well established in far-field acoustic wave scattering problems. The analysis results of a square flat plate compared with those obtained by other method show the accuracy of the proposed method. Moreover, it is noted that the sonar cross section is varied with respect to the targeting point as well as the range. Finally, numerical analysis results of real-like underwater target such as a submarine pressure hull are discussed.

• Journal of Welding and Joining
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• v.26 no.5
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• pp.66-73
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• 2008

Welding work in pre-erection or erection stage of shipbuilding construction to be carried out in flat and vertical upward position mostly and Electrogas welding(EGW) is actively applied especially for vertical butt joint of thicker steel plate recently. In this study considered how to develope and improve mechanical properties of weld metal and HAZ in high heat input welding processes such as EGW and Electroslag welding(ESW) with its welding equipment in order to extend the application range to the longitudinal members and hatch coaming parts of container ship. Some components of welding system and parameters were modified to get the faster travel speed and reduce weld heat input, and also by adding additional filler rods or tubes increase the amount of deposited weld metal. With the test get some good date can apply to actual fabrication work and recommend items to manufacture welding materials make better. Above all things it's a fruition that to prepare the possibility of application of ESW to shipbuilding construction which fill up the gap of stoppage days of more than 20 years.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2007.11a
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• pp.570-578
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• 2007

선체 외판 부재의 곡 성형 과정은 주로 가열(열간가공)에 의해 수행된다. 이 가열 작업은 작업자의 경험과 지식에 크게 의존하는 매우 어려운 작업이다. 본 논문에서는 선체 외판의 곡 성형을 위한 가열 계획을 자동으로 수립할 수 있는 휴리스틱을 소개한다. 현장 전문가의 지식에 기반한 이 휴리스틱은 크게 가열 선을 생성하는 부분과 외력을 주는 도구를 배치하는 부분으로 구성된다. 가열 선은 대상 부재의 현재 곡면과 설계된 목적곡면과의 비교를 통해 생성되고, 가우스 커널 함수를 통해 스무딩(smoothing)된다. 현장에서는 열간가공 시 의도하지 않은 변형을 막으면서 작업시간을 줄이고자 외력을 이용한다. 외력의 위치와 방향은 가열 선 군집화를 통해 추출된 대표 가열 선을 기준으로 결정된다. 가상의 인공 곡면과 현장의 실제 부재를 대상으로 실험한 결과, 이 휴리스틱이 숙련된 전문가가 수립한 가열 계획과 유사한 가열 계획을 수립할 수 있음을 확인하였다.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.6
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• pp.611-621
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• 2009

This paper first reviews the physical meanings and the expressions of two representative strain rate models: CSM (Cowper-Symonds Model) and JCM (Johnson-Cook Model). Since it is known that the CSM and the JCM are suitable for low-intermediate and intermediate-high rate ranges, many studies regarding marine accidents such as ship collision/grounding and explosion in FPSO have employed the CSM. A formula to predict the material constant of the CSM is introduced from literature survey. Numerical simulations with two different material constitutive equations, classical metal plasticity model based on von Mises yield function and micromechanical porous plasticity model based on Gurson yield function, have been carried out for the stiffened plates under impact loading. Simulation results coincide with experimental results better when using the porous plasticity model.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.1
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• pp.15-22
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• 2020

Understanding the strength characteristics of model ice is an important issue for model testing in an ice model basin to estimate the ship performance in ice. In particular, the mechanical properties of the model ice including elastic modulus, flexural strength and compressive strength are key consideration factors. In order to understand the characteristics of the model ice during warm-up phase at KRISO's ice model basin, the strength properties are tested in this study. The infinite plate-bending method, in-situ cantilever beam test and ex-situ uniaxial compressive test are conducted to determine the strength properties of model ice. The strength characteristics of the model ice are then analyzed in terms of the warm-up phase and seasonality. These results could be valuable to quality control of the model ice characteristics in KRISO's ice model basin and to better understand the variations in strength properties during the ice model tests.