• Journal of Welding and Joining
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• v.7 no.3
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• pp.44-54
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• 1989

This study was undertaken to evaluate the allowable welding heat input range for high strength steels manufactured by various processes and to compare the weldability of TMCP steel for high heat input welding with that of conventional Ti-added normalized steel. The allowable welding heat input ranges for conventional 50kg/$mm^2$ steel to guarantee D or E grade of ship structural steel were below 150 and 80kJ/cm respectively. Such a limit in welding heat input was closely related with the formation of undesirable microstructures, such as grain boundary ferrite and ferrite side plate in the coarse grain HAZ. In case of 60 and 80kg/$mm^2$ quenched and tempered steels, for securing toughness in weldments over toughness requirements for base metal, each welding heat input had to be restricted below 60 and 40kJ/cm, that was mainly due to coarsened polygonal ferrite in weld metal and lower temperature transformation products in coarse grain HAZ. The TMCP steel could be appropriate as a grade E ship hull steel up to 200kJ/cm, but the Ti-added normalized steel could be applied only below 130kJ/cm under the same rule. This difference was partly owing to whether uniform and fine intragranular ferrite microstructure was well developed in HAZ or not.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.374-380
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• 2016

The large drift and angle of attack motion of an ROV (Remotely operated vehicle) cannot be modeled using the typical hydrodynamic coefficients of conventional straight running AUVs and specific slender bodies. In this paper, the ROV hull is divided into several simple-shaped components to model the hydrodynamic force and moment. The hydrodynamic force and moment acting on each component are modeled as the components of added mass force and drag using the known values for simple shapes such as a cylinder and flat plate. Since an ROV is operated under the water, the only environmental force considered is the current effect. The target ROV dealt with in this paper has six thrusters, and it is assumed that its maneuvering motion is determined using a thrust allocation algorithm. Tracking simulations are carried out on the ship’s surface near the stern, bow, and midship sections based on the modeling of the hydrodynamic force and current effect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.155-162
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• 2009

Because the tonal sound of the underwater noise in a naval vessel can be identified from the sub-marine of the enemy, it should be reduced sufficiently. This kind of the noise usually comes from the structure-borne noise of the onboard machine and transfers to the sea through the hull of the ship. The vibration at the high frequency can be reduced sufficiently with damping material. In this paper, the damping coefficient of the steel plate with damping sheet is evaluated by experiment. Using these evaluated properties, the numerical analysis is performed in order to evaluate how much vibration of the generator can be reduced applying damping sheet on the encloser and base of it.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.41-49
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• 1994

The leak-before-break(LBB) design on the large structures such as ship's hull, tank structure, pressure vessels etc. is one of the most inportant subjects for the evaluation and the assurance of safety. In these structures, various loads are acting. In some structural members, therefore, out-of-plane stress due to bending often may become with in-plane stress due to stretching. In the present report, the characteristics of fatigue life and peneration behaviour from a surface cracked plate under combined tension and bending have been studied experimentally and analytically by using eccentricity. Estimation of fatigue crack growth was done with the Newman-Raju formula before penetration, and with the stress intensity factor after penetration proposed by the author. Calculated aspect ratio showed the good agreement with the experimental result. It was also found that particular crack growth behaviour and crack shape after penetration can be satisfactorily evaluated using the K solution proposed.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.4
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• pp.46-60
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• 1993

Accurate measurements of fluctuating pressure in the cavitation tunnel are necessary to predict vibration and noise intensities in full scale ship. In this paper, the results of an experimental study on fluctuating pressure induced by a cavitating propeller are presented and discussed. Extensive measurements at several propeller revolutions are made using the flat plate to understand controversial problems of the effects of propeller revolution in the cavitation tunnel. The analysis of the uncertainties in experimental measurements and results is used to estimate the errors in uniform flow.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1329-1337
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• 2009

Because the tonal sound of the underwater noise in a naval vessel can be identified from the sub-marine of the enemy, it should be reduced sufficiently. This kind of the noise usually comes from the structure-borne noise of the onboard machine and transfers to the sea through the hull of the ship. The vibration at the high frequency can be reduced sufficiently with damping material. In this paper, the damping coefficient of the steel plate with damping sheet is evaluated by experiment. Using these evaluated properties, the numerical analysis is performed in order to evaluate how much vibration of the generator can be reduced applying damping sheet on the encloser and base of it.

• International Journal of Naval Architecture and Ocean Engineering
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• v.1 no.2
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• pp.78-88
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• 2009

In shipbuilding industry, the manufacturing technology has advanced at an unprecedented pace for the last decade. As a result, many automatic systems for cutting, welding, etc. have been developed and employed in the manufacturing process and accordingly the productivity has been increased drastically. Despite such improvement in the manufacturing technology, however, development of an automatic system for fabricating a curved hull plate remains at the beginning stage since hardware and software for the automation of the curved hull fabrication process should be developed differently depending on the dimensions of plates, forming methods and manufacturing processes of each shipyard. To deal with this problem, it is necessary to create a "plug-in" framework, which can adopt various kinds of hardware and software to construct a full automatic fabrication system. In this paper, a framework for automatic fabrication of curved hull plates is proposed, which consists of four components and related software. In particular the software module for computing fabrication information is developed by using the ooCBD development methodology, which can interface with other hardware and software with minimum effort. Examples of the proposed framework applied to medium and large shipyards are presented.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.453-459
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• 2009

The DSME guide plate(GP) has been developed with the target to improve the cavitation and vibration performance when used with discharging cooling water around the outlet of LNG carrier. It was proven that it could as well be applied as a powerful wake control device on its own, even without discharging cooling water. However, it has to be taken into account that it inevitably results in speed loss. This study shows the possibility to design a GP which simultaneously improves both vibration and speed performance. The study intends to outline how to design the preliminary GP configurations from both the vibration and the speed performance points of view. Further, the study offers design guidance for the hull form and the propeller when adapting GP as a wake control device.

• Proceedings of KOSOMES biannual meeting
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• 2004.11a
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• pp.129-135
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• 2004

Plate has cutout inner bottom and girder and floor etc in hull construction absence is used much, and this is strength in case must be situated, but establish in region that high stress interacts sometimes fatally in region that there is no big problem usually by purpose of weight reduction, a person and change of freight, piping etc. Because cutout's existence gnaws in this place, and, elastic budding strength by load rouses large effect in ultimate strength. Therefore, perforated plate elastic budding strength and ultimate strength is one of important design criteria which must examine when decide structural elements size at early structure design step if ship. Therefore, and, reasonable elastic budding strength about perforated plate need design ultimate strength. Calculated ultimate strength change several aspect ratioes and cutout's dimension, and thickness in this investigation. Used program applied ANSYS F.E.M code based on finite element method

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.1
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• pp.80-87
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• 2021

Most container ships are currently being constructed as Ultra-Large Container Ships. Hence, the equipment of the ships is also becoming relatively large. In particular, propellers, rudders, and rudder stocks are large in the stern structure, and in relation, efficient design of the hull structures to safely secure these parts is important. The bottom shell plate surface of a stern skeg is a perforated plate from which the rudder stock penetrates, so it is an important component for the stern structure. In this paper, to determine the critical buckling of the shell plate, an interaction curve equation for the two-axis compression of the shell plate was derived using the maximum value of the static structural stress multiplier in a load multiplier mode. This equation predicts the timing of the buckling occurrence. By analyzing this interaction curve equation, the buckling behavior of the plates subjected to a combination load was determined and the usefulness of applying it to ship building was investigated.