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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Society of Naval Architects of Korea
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Journal DOI :
The Society of Naval Architects of Korea
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Volume & Issues
Volume 49, Issue 6 - Dec 2012
Volume 49, Issue 5 - Oct 2012
Volume 49, Issue 4 - Aug 2012
Volume 49, Issue 3 - Jun 2012
Volume 49, Issue 2 - Apr 2012
Volume 49, Issue 1 - Feb 2012
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On the Fracture of Polar Class Vessel Structures Subjected to Lateral Impact Loads
Min, Dug-Ki ; Cho, Sang-Rai ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 281~286
DOI : 10.3744/SNAK.2012.49.4.281
Single frame structures with notches were fractured by applying drop impact loadings at room temperature and low temperature. Johnson-Cook shear failure model has been employed to simulate the fractured single frame structures. Through several numerical analyses, material constants for Johnson-Cook shear failure model have been found producing the cracks resulted from experiments. Fracture strain-stress triaxiality curves at both room temperature and low temperature are presented based on the extracted material constants. It is expected that the fracture strain-stress triaxiality curves can offer objective fracture criteria for the assessment of structural fractures of polar class vessel structures fabricated from DH36 steels. The fracture experiments of single frame structures revealed that the structure on low temperature condition fractures at much lower strain than that on room temperature condition despite the same stress states at both temperatures. In conclusion, the material properties on low temperature condition are essential to estimate the fracture characteristics of steel structures operated in the Northern Sea Route.
Numerical Analysis of Hydrodynamic Performance of a Movable Submerged Breakwater Using Energy Dissipation Model
Kim, Do-Hyun ; Koo, Weon-Cheol ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 287~295
DOI : 10.3744/SNAK.2012.49.4.287
Hydrodynamic performance of a movable submerged breakwater was analyzed using energy dissipation model. Based on two-dimensional boundary element method the equation of motion including a viscous dissipation term proportional to velocity squared was solved by Newton-Raphson method. Energy dissipation coefficients as well as reflection and transmission coefficients of a submerged flat plate were calculated with various plate lengths and thickness. Both real and imaginary components of body displacement and forces were used to solve the motion of breakwater accurately. The effect of the magnitude of dissipation coefficient on the body displacement was evaluated. The results from the potential theory with no dissipation term were found to be an overestimate in resonance frequency.
Captive Model Test of Submerged Body Using CPMC
Kim, Yeon-Gyu ; Yun, Kun-Hang ; Kim, Sun-Young ; Kim, Dong-Jin ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 296~303
DOI : 10.3744/SNAK.2012.49.4.296
The captive model test of submerged body using CPMC(Computerized Planar Motion Carriage) was carried out at the Ocean Basin of KORDI/MOERI. The target model is a submarine with general hullform. The forces and moments acting on the submerged body were measured by 6-axis waterproof gage. The oblique motion test and turning test were carried out in horizontal and vertical planes of the model. Maneuvering coefficients and derivatives were obtained from the test results. The stability indices in horizontal and vertical planes were obtained by using maneuvering derivatives. In this paper the introduction of test equipment and test results are presented.
Thermal Distortion Analysis by Inconel Over-lay at Circular Moonpool Structures
Ha, Yun-Sok ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 304~311
DOI : 10.3744/SNAK.2012.49.4.304
One of the main features of Drillship or FPSO is a moonpool structure. The moonpool structures have various accuracy tolerances according to their functions and targets. This study is mainly interested in roundness of a circular moonpool structure in FPSO. Because this structure needs abrasion-resistance at which bearing of machine touches on inner wall of moonpool, we should do over-lay welding widely and deeply by using Inconel weld material. But a general over-lay can cause a severe distortion at ship block structure. If we can analyze the roundness by thermal distortion under Inconel over-lay, we can establish a special erection policy by the results. In this study, we designed stress-strain curve for strain-boundary condition analysis by an elasto-plastic material property. The results made us to decide an appropriate ship-block size and policy of crane manipulation will follow for its capacity. If a structure that needs over-lay is not large, solid elements also are not a bad choice for FEM modeling. Therefore we also developed a standard of using strain-boundary method that shell elements are used as over-lay on solid element modeling.
Analysis on the Hydroelasticity of Whole Ship Structure by Coupling Three-dimensional BEM and FEM
Kim, Kyong-Hwan ; Bang, Je-Sung ; Kim, Yong-Hwan ; Kim, Seung-Jo ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 312~326
DOI : 10.3744/SNAK.2012.49.4.312
This paper considers a fully coupled 3D BEM-FEM analysis for the ship structural hydroelasticity problem in waves. Fluid flows and structural responses are analyzed by using a 3D Rankine panel method and a 3D finite element method, respectively. The two methods are fully coupled in the time domain using a fixed-point iteration scheme, and a relaxation scheme is applied for improve convergence. In order to validate the developed method, numerical tests are carried out for a barge model. The computed natural frequency, motion responses, and time histories of stress are compared with the results of the beam-based hydroelasticity program, WISH-FLEX, which was thoroughly validated in previous studies. This study extends to a real-ship application, particularly the springing analysis for a 6500 TEU containership. Based on this study, it is found that the present method provides reliable solutions to the ship hydroelasticity problems.
On the Crabbing Tests of Cruise Vessel Equipped with Bow Thrusters and POD System
Yeo, Dong-Jin ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 327~332
DOI : 10.3744/SNAK.2012.49.4.327
International Towing Tank Conference (ITTC) recommended verifying a ship`s ability to move transversely at zero forward speed without altering heading by a crabbing test. In sea trial, all available propellers/rudders/thrusters should be used to find the maximum possible transverse speed. For estimating crabbing ability in the design stage, tests to estimate possible swaying force and yawing moment range using all available propellers/rudders/thrusters are conducted. By butterfly diagram, which compares possible swaying force and yawing moment range with external swaying force and yawing moment by wind, a ship`s crabbing ability can be estimated. In this study, model tests of a cruise vessel equipped with bow thrusters and POD system were conducted to find out her crabbing ability in the design stage. To mimic quay condition, a model quay-wall was set in the towing tank.
Study on the Drag Reduction of 2-D Dimpled-Plates
Paik, Bu-Geun ; Pyun, Young-Sik ; Kim, Jun-Hyung ; Kim, Kyung-Youl ; Kim, Ki-Sup ; Jung, Chul-Min ; Kim, Chan-Ki ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 333~339
DOI : 10.3744/SNAK.2012.49.4.333
The main objective of the present study is to investigate the roles of the micro-dimpled surface on the drag reduction. To investigate the effectiveness of the micro-dimpled surface, the flat plates are prepared. The micro-size dimples are directly carved on the metal surface by ultrasonic nano-crystal surface modification (UNSM) method. Momentum of the main flow is increased by the dimple patterns within the turbulent boundary layer (TBL), however, there is no significant change in the turbulence intensity in the TBL. The influence of dimple patterns is examined through the flow field survey near the flat plate trailing edge in terms of the profile drag. The wake flow velocities in the flat plate are measured by PIV technique. The maximum drag reduction rate is 4.6% at the Reynolds number of
. The dimples tend to increase the drag reduction rate consistently even at high Reynolds number range.
Study on Parameters for Optimum Design of Integrated Subsea System
Choi, Han-Suk ; Do, Chang-Ho ; Lee, Seung-Keon ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 340~349
DOI : 10.3744/SNAK.2012.49.4.340
The mitigation of gap between technology and it`s applicability in the oil and gas industry has led to a rapid development of deepwater resources. Historically, subsea wells have good track records. However, an ever increasing water depths and harsher environments being encountered are currently posing challenges to subsea production. Complex subsea systems are now being deployed in ways rarely encountered in previous development schemes. These increasingly complex systems present a number of technical challenges. This study presents the challenges in subsea production systems, considering the technical and safety issues in design and installation associated with current development modality.
Study on Applicability of Frequency Domain-Based Fatigue Analysis for Wide Band Gaussian Process I : Rayleigh PDF
Choung, Joon-Mo ; Kim, Kyung-Su ; Nam, Ji-Myung ; Koo, Jeong-Bon ; Kim, Min-Soo ; Shim, Yong-Lae ; Urm, Hang-Sub ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 350~358
DOI : 10.3744/SNAK.2012.49.4.350
This paper deals with accuracy of accumulated fatigue damage estimation using stochastic fatigue analysis method based on Rayleigh PDF. From full scale measurement data on an 8100TEU container vessel, zero-order spectral moments for wave- and vibration-induced energy spectral densities are determined on the probability level of 99%. 80 simulation cases in total are prepared according to the variation of ratio of zero-order spectral moments and center frequency of vibration ESD. By using inverse Fourier transformation and rainflow cycle counting for the combined ESD of wave and vibration, exact fatigue damages are derived. Fatigue damages in frequency domain based on Rayleigh PDF show large conservativeness compared to exact fatigue damages in times domain. The main cause of the excessive conservativeness is analyzed by two aspects: ratio of zero crossing and peak frequencies and ratio of initial zero order spectral moments and zero order spectral moments from rainflow stress range distributions. Finally, a guideline of applicability of Rayleigh PDF is proposed for wide band processes.
Study on Applicability of Frequency Domain-Based Fatigue Analysis for Wide Band Gaussian Process II : Wide Band Prediction Models
Choung, Joon-Mo ; Kim, Kyung-Su ; Nam, Ji-Myung ; Koo, Jeong-Bon ; Kim, Min-Soo ; Shim, Yong-Lae ; Urm, Hang-Sub ;
Journal of the Society of Naval Architects of Korea, volume 49, issue 4, 2012, Pages 359~366
DOI : 10.3744/SNAK.2012.49.4.359
This is the final one of the two companion papers dealing with accuracy of accumulated fatigue damage estimation under wide band process. It is stated that four kinds of wide band models exist: typed of equivalent stress, combined PDF, correction factor, and damage combination. For the idealized ESDs from full scale measurement data on an 8100TEU container vessel, fatigue damages are compared for a narrow band prediction model based on Rayleigh PDF and five wide band fatigue prediction models of Dirlik, Wirsching-Light, Jiao-Moan, Benasciutti and DNV. DNV model consistently overestimates fatigue damages regardless of variation of ESDs. Predictions by Jiao-Moan model, which is understood as standard method for design of offshore platforms, are also in conservative side. Best accuracy is found from the results by Dirlik and Benasciutti models, but Benasciutti model is preferred since it can easily combined with narrow band fatigue damage based on Rayleigh PDF.