• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.301-305
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• 2010

Cutting procedures where qualities are determined by various demand factors largely influences shipbuilding productivity. Particularly, defects in cutting shapes and cutting surface results in delay for post shipbuilding stages such as in welding and assemblage lines which could become factors for reduced economic viability of the project. Existing cutting procedures utilize fossil fuels such as propane or ethylene as the main fuel component and these methods applied particularly to ship plate cutting gives relatively slow cutting speed and generates large quantities of harmful and sometimes poisonous polluting fumes of which warrants an urgent need to look for alternative cutting methods. Recent introduction of hydrox gas generated by electrically dissociating water into hydrogen and oxygen components to be utilize as an alternative cutting fuel has resulted not just in visible improvement on cutting quality and speed over the existing methods but it has also been welcomed as an environmentally friendly clean fuel source. This paper has been prepared to serve as the basis for accommodating this environmentally friendly hydrox gas cutting method into actual working environment by observing and recording hydrox gas cutting thermal characteristics.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.3
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• pp.263-269
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• 2015

Growing concerns regarding air pollution have recently increased the demand for liquefied natural gas (LNG) fueled ships. LNG-fueled ships are equipped with an explosion relief valve in the crankcase to relieve excessive pressure and stop flames from emitting from the crankcase. In this study, a finite element analysis was conducted to evaluate the crankcase relief valve disk spring design using an ANSYS Workbench, v.15. The setting pressure, leak and explosion test performed by european standard EN14797 to evaluate function and mechanical integrity of crankcase relief valve. The tests results indicate that the pressure of the crankcase relief valve is 3.05 bar, with no air leakage at 2.97 bar. Finally, the mechanical integrity of the crankcase relief valve was confirmed through an explosion test in which the valve plate assembly, flame arrester, and other parts were safe from fracturing.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.768-772
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• 2008

Various scanning systems have been studied in many industrial areas to acquire a range data or to reconstruct an explicit 3D model. Currently optical technology has been used widely by virtue of noncontactness and high-accuracy. In this paper, we describe a 3D laser scanning system developped to reconstruct the 3D surface of a large-scale object such as a curved-plate of ship-hull. Our scanning system comprises of 4ch-parallel laser vision modules using a triangulation technique. For multi laser vision, calibration method based on least square technique is applied. In global scanning, an effective method without solving difficulty of matching problem among the scanning results of each camera is presented. Also minimal image processing algorithm and robot-based calibration technique are applied. A prototype had been implemented for testing.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.11
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• pp.919-925
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• 2016

In this study, multibody dynamic and mechanical analyses were conducted for the structure of roller chain bucket elevator system. The fatigue life of the roller chain elevator system was determined under static and fatigue loadings. Results of multibody dynamic analysis suggested that the maximum contact force occurred at the drive sprocket engagement point with the roller chain due to maximum tension. Fatigue analysis results suggest that the high load roller chain system is durable and safe because its life time is more than 700,000 cycles, close to its designed value (1,000,000 cycle). However, the contact portion of plate and pin needed a safety factor. The dynamic analysis of the heavy load roller chain was conducted with a multibody dynamic analysis program. The results obtained in this study can be utilized for dynamic analysis of roller chain systems in all industries.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.295-304
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• 2001

The hydrodynamic impact problem was studied from 1929 to recent. Especially, Impact pressure is important for the design of the ships and offshore structure and spacecrafts, and under weapons. A ship traveling at high speed or in heavy sea has its bow and bottom damaged by high pressure caused by impact with and detachment from the water surface. Considerable impact may also occur when large waves hit the cross member or deck plate of an offshore structure within the splash zone. Many engineering cases require consideration of impact pressure, the movement of objects and change of the flow field. This study was obtained the pressure distribution of a falling body that is deadrise angle $0^{\circ}$ and deadrise angle $5^{\circ}$ upon a water surface by the experiment with the impact machine. The theoretical equation was obtained the air region and the interface and the water region which devide 3 parties between the body and the water surface for an investigation of the complete phenomena. Pressure distributions and histories compare favorably with available experimental data. The numerical results are similar to the experimental results for the impact force type with Fo(1+$cos{\pi}t/tc$).

• Journal of Welding and Joining
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• v.3 no.2
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• pp.52-63
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• 1985

Fillet welded joints, specially in ship structure, are well known the critical part where stress concentrate or crack initiates and grows. This paper is concerned with the study of the behavior of fatigue crack growth t the root and toe of load carrying cruciform fillet welded joints under three points bending by the determination of stress intensity factor from the J-Integral, using the Finite Element Method. The stress intensity factor was investigated in accordance to the variation of the weld size (H/Tp). weld penetration (a/W) and plate thickness (2a'/Tp). As mixed mode is occurred on account of shearing force under the three points bending, Stern's reciprocal theory is applied to confirm which mode is the major one. The main results may be summarized as follows 1) The calculation formula of the stress intensity factor at the both of root and toe of the joint was obtained to estimate the stress intensity factor in the arbitrary case. 2) The change of stress field around crack tip gives much influence on each other at the roof and toe as H/Tp decreases. 3) Mode I is a major mode under the three points bending.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.139-149
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• 1991

In this paper, an efficient method for the ultimate longitudinal strength analysis of the double skin hull girder is presented by using idealized structural unit method. Idealized plate element subjected to biaxial load is developed taking account of initial deflection and welding residual stress. Interaction effect between local and global buckling in the whole structure is also taken into consideration. The reserve strength factor and reliability index for the example 40K double skin product oil carrier are evacuated against the ultimate longitudinal strength. It is concluded that the prudent method seems to be useful in the sense that the computing time required is very short while giving the reasonable solution.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.1-11
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• 1991

When a geometric modeling of a hull form for ship design and hull production is done, a hull fairing is a tedious process which wastes a lot of time, but it is unavoidable because hull consist of the sculptured surfaces. This paper presents the mathematical method of the direct fairing to overcome the tediousness of cross fairing. Bi-cubic B-spline surface description was adopted for the representation of the hull surface. The fairing process was executed by minimizing the strain energy in a shell plate. The color-encoded Gaussian curvature and strain energy were visualized on the screen to illustrate the fairness of the surface. The geometric information generated from the faired hull surface model was interfaced with the basic design calculation package and the hull production system.

• Special Issue of the Society of Naval Architects of Korea
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• 2007.09a
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• pp.99-106
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• 2007

The IACS Common Structural Rules are to be applied for double hull tanker of more than 150m length with contracted after 1 April 2006. The objectives of the rules are to make more robust, safer ship and to ensure transparency of the technical background. In compliance of CSR, we had carried out prescriptive rules scantling determination and 3-D hold FE analysis of AFRAMAX TANKER. Prescriptive rules scantling determines the minimum required scantling, hull-girder longitudinal bending and shear strength, hull girder ultimate strength, local strength of plate and stiffener, strength of primary supporting member and fatigue assessment of the longitudinal stiffener end connections to the transverse bulkhead. 3-D hold FE analysis assesses the structural adequacy of the vessel's primary hull structure and major supporting members using yielding and buckling failure modes. So we could verify the strength assessment of AFRAMAX TANKER applied CSR.

• Bulletin of the Society of Naval Architects of Korea
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• v.7 no.1
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• pp.1-12
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• 1970

The propeller induced pressure fluctuation around a ship's stern is one of the interesting problems from viewpoints of the noise and vibration. Most of the experimental works on the subject employ pressure transducer attached on hull surface near the propeller. In the technique, the measured pressure includes the hydrodynamic pressure transducer attached, if they exit. Hence, the separation of the additional pressure due to vibration from the measured pressure is essential for the determination of true values of the propeller induced pressure. In this paper, to contribute to the separation method, the author investigated the additional hydrodynamic pressure as below, based on the numerical calculation. (1) Hydrodynamic pressure on the body surface of two dimensional cylinders of some mathematical sections such as ellipse, rectangle, Lewis form of hypotrocoidal charactor and curvilinear-element section with chines oscillating vertically at high frequency in a free surface. (2) Hydrodynamic pressure on the surface of the shell plate in local vibration in an ideal fluid.