• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.179-183
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• 2005

The High-tensile steel has been recognized as a promising concept for structural design of light weight transportation systems such as aircraft high speed trains and fast ships. Using the high-tensile steel has been widely used in ship structures, and this enables to reduce the plate thickness. Using the high-tensile steel effectively for a ship hull, the plate thickness becomes thin so that plate buckling may take place. Therefore, precise assessment of the behavior of plate above primary buckling load is important. In this study, examined closely secondary buckling behavior after initial buckling of thin plate structure which operated compressive load according to the various kinds of yield stress with simply supported boundary condition. Analysis method is F.E.M by commercial program(ANSYS V7.1) and complicated nonlinear behaviour can analyze using art-length method about secondary buckling.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.399-404
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• 2015

The cost of fuel in ships has recently increased due to a rapid increase in international oil prices and international restrictions regarding the greenhouse effect generated from the burning of fuel. Therefore, different methods for changing the hull designs for improving energy efficiency, developing coating for reducing friction resistances, developing additives for improving engine thermal efficiency, and low-speed operation for reducing fuel consumption have been considered. The developments of high-speed, large-scale, and energy-saving vessels are deemed essential to adapt to the recent high oil price era. Therefore, it is important to analyze Precisely the qualitative and quantitative changes in the resistance value of the local areas of the hull surface. In this study, the engine performance before and after docking was analyzed to examine friction resistance caused by marine growth on the hull as a basic study for improving the energy efficiency. The result was then presented by comparing it with the previous data for 2.5 years between docks to investigate the performance of the main engine, the change in friction resistances and loads, the fuel consumption and ship speed.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.237-245
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• 2020

In decades, active sonar, which transmits signals and detects incident signals reflected by underwater targets, has been significantly studied since passive sonar in Anti-Submarine Warfare (ASW) detection performance becomes lowered, as underwater threats become their radiated noise reduced. In general, active sonar using Hull-Mounted Sonar (HMS) adjusts vertical tilt (depression) and sequentially transmits multiple Linear Frequency Modulation (LFM) subpulses which have non-overlapped bands, i. e. 1 kHz ~ 2 kHz, 2 kHz ~ 3 kHz, in order to reduce shadow zones. Recently, however, Generalized SFM (GSFM), which is generalized form of SFM, is proposed, and it is confirmed that subpulses of GSFM have orthogonality among each other depending on setting of GSFM parameters. Hence, in this paper, we applied GSFM to active target detection using HMS to improve the performance by the signal processing gain obtained from enlarged bandwidths of GSFM subpulses compared to those of LFM subpulses. Through simulation, we verified that when the number of subpulses is three, the matched filter gain of GSFM is approximately 5 dB higher than that of LFM.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.905-910
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• 2007

As the ship is getting bigger and faster lately, ship's structure or cargoes might be often damaged and the ship might be cut in two in extreme conditions by a wave impact on its bow. In this paper, the vertical acceleration, which is one of factors for evaluating seakeeping performance, was measured under the various sea states by the hull stress monitoring system(HMS) on the bridge, and the result was compared with those of model test and theoretical studies. Then, we confirmed the seakeeping performance of T.S. HANBADA by comparing it with ITTC seakeeping criteria This result will be a great help for the safe navigation by making it possible to estimate the possibility of work and the amount of risk under the various sea conditions with which may be confronted, and the shipbuilding yard can be possible to construct the vessel with superior performance through these data measured on the actual ship.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.149-154
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• 2013

This paper considers the issue of LSS(Liquid Spill Stopper)'s performance verification testing against external resisting force. The importance of the test is to ascertain the possibility of liquid spill stop quickly and efficiently by LSS. The method adopted in this research is the experimental device for puncture's inflow pressure and test the adhesive (magnetic) force on shell plates during the sailing. The major results of the paper are the followings : (a) The performance of LSS against 40 and 100mm diameter puncture was confirmed under 1.0bar. (b) LSS near bow detached first at 20.2 knots. This indicates that LSS can recover the damaged movability needed to naval warships' operation as well as merchant ships.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.62-73
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• 2001

The interest in evaluation of structural intensity arises for practical reasons, because net energy flow distribution offers information of energy transmission path, positions of sources, and sinks of vibration energy. In this paper, structural intensity analysis of local ship structures using finite element method(FEM) is carried out. The purpose of this analysis is to evaluate the relative accuracy according to mesh fineness. The structural intensity of unstiffened and stiffened plates varying their mesh fineness is analyzed and the results are compared with those obtained by the assumed mode method. As results, the proper mesh size in qualitative/quantitative structural intensity analysis of plate structures is proposed. In addition, the propagation phenomenon of vibration energy is investigated for the thickness-varying flat plate, L-type plate, and box-girder structures.

• Composites Research
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• v.34 no.6
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• pp.350-356
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• 2021

When a ship with a planing line operates or turns in a straight line, the floating position and trim change according to the speed, and a large resistance is generated on the hull. In this paper, the resistance to a planing line was estimated through the computational fluid dynamics of a leisure boat with improved hull weight and durability by applying a carbon composite material to the hull. The resistance performance of the bow and stern of the 18ft class leisure boat was checked and the flow field of the entire vessel was estimated, and the stability of the planing line was confirmed by comparing the resistance of each trim through numerical analysis. In addition, it was confirmed that the designed planing line could withstand it sufficiently because the force applied to the hull was not large, and The stability of the boat was analyzed by calculating the wavelength of the wave and the length of the ship as the ratio of gravity to the inertial force and checking how much force the rolling occurred.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.106-111
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• 2005

After many casualties of conventional bulk carriers in recent years, a double hull bulk carrier was proposed to enhance the structural safety of a side shell and a transverse bulkhead. In this paper, two alternative structural designs of a double hull bulk carrier were carried out based on the Lloyd's rule. One has the double sided hull with longitudinal stiffeners and the other has that with a girder. The final structural design was examined in comparison with an existing single hull bulk carrier from the viewpoints of cargo hold capacity and the increases of weight and construction cost. Generally, the construction cost of a ship consists of the costs of material, labor and overhead cost. But, in this study, the relative construction cost concept was introduced to compare the economical validity more precisely. In this concept, fixed overhead cost is excluded in the assessment of construction cost, and only the variable overhead cost is added up to labor cost. As the result of this study, a double hull bulk carrier can be constructed within 1% increase of weight and construction cost.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.103-117
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• 1995

A design-oriented method for analysis of the structural damage due to ship collisions is developed by using the idealized structural unit method(ISUM). The method takes into account yielding, crushing, rupture, the coupling effects between local and global failure of the structure, the influence of strain-rate sensitivity and the gap/contact conditions. The method is verified by a comparison of experimetal and numerical results obtained from test models of double-skin plated structures in collision/grounding situations with the present solutions. As an illustrative example, the method has been used for analyses of a side collision of a double-hull tanker. Several factors affecting ship collision response. namely the collision speed and the scantlings/arrangements of strength members, are discussed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.3
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• pp.211-216
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• 2013

Most of hull resistance prediction methods which are used to calculate the towing force of disabled ships are very simple and old-fashioned. In particular, in cases of barge ships, a method similar to the US Navy Towing Manual is being used. This paper reviewed the US Navy Towing Manual and the notification method of Korea Ministry of Oceans and Fisheries and proved that these prediction methods are irrational and inaccurate. Furthermore, a new Modified-Yamagata-Barge method is introduced as a more rational and accurate resistance prediction method which can be applied in case of barge ships.