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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Ocean System Engineering
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Korean Society of Ocean Engineers
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Volume 2, Issue 4 - Nov 2012
Volume 2, Issue 3 - Aug 2012
Volume 2, Issue 2 - May 2012
Volume 2, Issue 1 - Feb 2012
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Kinematic Displacement Theory of Planar Structures
Tayyar, Gokhan Tansel ; Bayraktarkatal, Ertekin ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 63~70
DOI : 10.5574/IJOSE.2012.2.2.063
This paper presents a new curvature based kinematic displacement theory and a numerical method to calculate the planar displacement of structures from a geometrical viewpoint. The theory provides an opportunity to satisfy the kinematic equilibrium of a planar structure using a progressive numerical approach, in which the cross sections are assumed to remain plane, and the deflection curve was evaluated geometrically using the curvature values despite being solved using differential equations. The deflection curve is parameterized with the arc-length, and was taken as an assembly of the chains of circular arcs. Fast and accurate solutions of most complex deflections can be obtained with few inputs.
Investigation of Dimension Changes in Under Pressure Hydraulic Sediment Flushing Cavity of Storage Dams Under Effect of Localized Vibrations in Sediment Layers
Dodaran, Asgar Ahadpour ; Park, Sang-Kil ; Mardashti, Asadollah ; Noshadi, Masoud ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 71~81
DOI : 10.5574/IJOSE.2012.2.2.071
Several methods have been proposed to control the sedimentation process. These include catchment management, flushing, sluicing, density current venting, and dredging. Flushing is used to erode previously deposited sediments. In pressurized flushing, the sediment in the vicinity of the outlet openings is scoured and a funnel shaped crater is created. In this study, the effect of localized vibrations in the sediment layers on the dimensions of the flushing cone was investigated experimentally. For this purpose, experiments were carried out with two bottom outlet diameters, five discharge releases for each desired water depth, and one water depth above the center of the bottom outlets. The results indicate that the volume and dimensions of the flushing cone are strongly affected by localized vibrations.
Numerical Simulation of Welding Residual Stress Distribution on T-joint Fillet Structure
Hwang, Se-Yun ; Lee, Jang-Hyun ; Kim, Sung-Chan ; Viswanathan, Kodakkal Kannan ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 82~91
DOI : 10.5574/IJOSE.2011.2.2.082
Fillet welding is widely used in the assembly of ships and offshore structures. The T-joint configuration is frequently reported to experience fatigue damage when a marine structure meets extreme loads such as storm loads. Fatigue damage is affected by the magnitude of residual stresses on the weld. Recently, many shipping registers and design guides have required that the fatigue strength assessment procedure of seagoing structures under wave-induced random loading and storm loading be compensated based on the effect of residual stresses. We propose a computational procedure to analyze the residual stresses in a T-joint. Residual stresses are measured by the X-ray diffraction (XRD) method, and a 3-D finite element analysis (FEA) is performed to obtain the residual stress profile in the T-joint. The proposed finite element model is validated by comparing experiments with computational results, and the characteristics of the residual stresses in the T-joint are discussed.
Rockfall Impact Analysis of Typical Roadway Using Finite Element Simulation
Woo, Jin-Ho ; Na, Won-Bae ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 92~96
DOI : 10.5574/IJOSE.2012.2.2.092
This study presents a rockfall impact analysis of a typical roadway. Dynamic finite element analyses using ANSYS AUTODYN are conducted to determine the effect of the drop heights (5 m, 10 m) on the damage to a roadway model. The Rockfall is modeled as a spherical shape with a weight of 400 kg, and each drop height is converted to a corresponding impact velocity to save computational time. The roadway model is comprised of an asphalt layer, base layer, sub-base layer, and sub-grade layer. In this paper, the asphalt is modeled using a linear elastic model. The base layer, sub-base layer, and sub-grade layer are modeled using a Mohr-Coulomb model. From the analyses, the effects of the drop height on the damages and stresses are examined and discussed.
Development of Design Static Property Analysis of Mooring System Caisson for Offshore Floating Wind Turbine
Dodaran, Asgar Ahadpour ; Park, Sang-Kil ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 97~105
DOI : 10.5574/IJOSE.2012.2.2.097
A all floating structures operating within a limited area require, stationkeeping to maintain the motions of the floating structure within permissible limits. In this study, methods for selecting and optimizing the mooring system Caisson for floating wind turbines in shallow water are investigated. The design of the mooring system is checked against the governing rules and standards. Adequately verifying the design of floating structures requires both numerical simulations and model testing, the combination of which is referred to as the hybrid method of design verification. The challenge in directly scaling moorings for model tests is the depth and spatial limitations of wave basins. It is therefore important to design and build equivalent mooring systems to ensure accurate static properties (global restoring forces and global stiffness).
Adhesive Behaviors of the Aluminum Alloy-Based CrN and TiN Coating Films for Ocean Plant
Murakami, Ri-Ichi ; Yahya, Syed Qamma Bin ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 106~115
DOI : 10.5574/IJOSE.2012.2.2.106
In the present study, TiN and CrN films were coated by arc ion plating equipment onto aluminum alloy substrate, A2024. The film thickness was about 4.65
. TiN and CrN films were analyzed by X-ray diffraction and energy dispersive X-ray equipments. The Young`s modulus and the micro-Vickers hardness of aluminum substrate were modified by the ceramic film coatings. The difference in Young`s modulus between substrate and coating film would affect on the wear resistance. The critical load, Lc, was 75.8 N for TiN and 85.5 N for CrN. It indicated from the observation of optical micrographs for TiN and CrN films that lots of cracks widely propagated toward the both sides of scratch track in the early stage of MODE I. TiN film began to delaminate completely at MODE II stage. The substrate was finally glittered at MODE III stage. For CrN film, a few crack can be observed at MODE I stage. The delamination of film was not still occurred at MODE II and then was happened at MODE III. This agrees with critical load measurement which the adhesive strength was greater for CrN film than for TiN film. Consequently, it was difficult for CrN to delaminate because the adhesive strength was excellent against Al substrate. The wear process, which the film adheres and the ball transfers, could be enhanced because of the increase in loading. The wear weight of ball was less for CrN than for TiN. This means that the wear damage of ball was greater for TiN than for CrN film. It is also obvious that it was difficult to delaminate because the CrN coating film has high toughness. The coefficient of friction was less for CrN coating film than for TiN film.
Semi-Analytical Methods for Different Problems of Diffraction-Radiation by Vertical Circular Cylinders
Malenica, Sime ;
International Journal of Ocean System Engineering, volume 2, issue 2, 2012, Pages 116~138
DOI : 10.5574/IJOSE.2012.2.2.116
As in the other fields of mechanics, analytical methods represent an important analysis tool in marine hydrodynamics. The analytical approach is interesting for different reasons : it gives reference results for numerical codes verification, it gives physical insight into some complicated problems, it can be used as a simplified predesign tool, etc. This approach is of course limited to some simplified geometries (cylinders, spheres, ...), and only the case of one or more cylinders, truncated or not, will be considered here. Presented methods are basically eigenfunction expansions whose complexity depends on the boundary conditions. The hydrodynamic boundary value problem (BVP) is formulated within the usual assumptions of potential flow and is additionally simplified by the perturbation method. By using this approach, the highly nonlinear problem decomposes into its linear part and the higher order (second, third, ...) corrections. Also, periodicity is assumed so that the time dependence can be factorized i.e. the frequency domain formulation is adopted. As far as free surface flows are concerned, only cases without or with small forward speed are sufficiently simple to be solved semi-analytically. The problem of the floating body advancing in waves with arbitrary forward speed is far more complicated. These remarks are also valid for the general numerical methods where the case of arbitrary forward speed, even linearized, is still too difficult from numerical point of view, and "it is fair to say that there exists at present no general practical numerical method for the wave resistance problem" , and even less for the general seakeeping problem. We note also that, in the case of bluff bodies like cylinders, the assumptions of the potential flow are justified only if the forward speed is less than the product of wave amplitude with wave frequency.