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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 29, Issue 4 - Nov 1992
Volume 29, Issue 3 - Aug 1992
Volume 29, Issue 2 - May 1992
Volume 29, Issue 1 - Mar 1992
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Applications of the Type III Asymptotic Distribution for Extreme Sea Level Computations
T.I. Lee ; S.H. Kwon ; Y.K. Chon ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 1~7
The computational methods of extreme sea level are developed in this study. Based on type III asymptotic distribution, non-linear multiple regression method, skewness method and maximum likelihood method are used to evaluate the parameters of the distribution. The difference between real data and evaluated distribution function is fitted to get more desirable accuracy by employing polynominals. The numerical examples are given in the last section in order to illustrate the application of the present scheme.
Ship Lines Creation by B-Spline Form Parameter Method
S.Y. Kim ; S.W. Kang ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 8~17
There has been considerable reseach on the representation of a hull form which is a 3-dimensional free surface. A form parameter method to describe the hull form by means of form parameters which represent the characteristics of the given hull form geometry has been recently paid special attention with the advent of powerful computer. However, there have been reported many problems to the conventional form parameter for the practical hull form generation. In the present paper, an attempt has been made to creak hull form by combining the form parameter method with the B-spline curve which can be best fitted to free surfaces. In an application, the present method is used to generates a Bulk carrier hull form and compared with the existing hull form to prove its applicability for the hull form generation.
A Survey of the Computer Graphics Standards
Soon-Hung Han ; Seung-Wan Suh ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 18~29
As more application programs have graphic functions, standards in the computer graphics are becoming important. To develop a computer aided design and production system for ships, which would be used by different shipyards, a graphic library should be chosen as a standard. Existing ISO graphic standards and de facto industrial standards are surveyed. They are, to name some of them, GKS, PHIGS, X-Window, PEX, PDES, and STEP. GKS and PHIGS concern about the application programmer's interface. Others handle the device interface. PDES and STEP are to standardize the graphical data transfer between heterogeneous systems. Their inter-relations are investigated. Some preliminary suggestions for the choice of graphic standards are included in this paper.
Representation of Structural Surface for Hull Modeling
Kwang-Wook Kim ; Won-Don Kim ; Jong-Ho Nam ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 30~37
Since a ship is a complex steel construction which consists of sculptured surfaces and inner surface members, a high technique of information modeling is indispensable to describe the form of hull surface and steel structure members consistently. A model contains both topological and geometrical information of the structural members. Therefore, the hull form should be represented by the wireframe of surface model so that the accuracy in each design stage is satisfied. The structural members like plane surfaces, stiffeners and the relations between such members are to be described systematically in data base. A collection of the data stored in database is a model to be built. The model will be used not only to generate the drawings and documents for ship design and production but also to interconnect other systems such as compartmentation, outfitting, piping, etc. Computer graphics is adopted of the visualization of model.
Wave Responses and Ship Motions in a Harbor Excited by Long Waves(I)
I.H. Cho ; Hang-S. Choi ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 38~47
The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Within the framework of potential theory, matched asymptotic expansion techniques are exployed to analyze the problem. The fluid domain is divided into the ocean and the harbor regions for the analysis of wave response in a harbor without ship. The wave responses in both the ocean and the harbor sides are solved first independently in terms of Green's functions, which are the solutions of the Helmholtz equation satisfying appropriate boundary conditions. Slender body approximations are used to obtain the velocity jumps across the ship, which are associated with the symmetric motion modes of the ship. Unknowns contained in each solution are finally determined by matching at an intermediate zone between two neighboring regions. Theoretical results predict the ship motion qualitatively well. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.
A Deformation Model of a Bag-Finger Skirt and the Motion Response of an ACV in Waves
G.J. Lee ; K.P. Rhee ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 48~59
In this paper, the effects of a skirt deformation on the responses of an Air Cushion Vehicle in waves are investigated. The air in the bag and in the plenum chamber is assumed to be compressible and to have a uniform instantaneous pressure distribution in each volume. The free surface deformation is determined in the framework of linear potential theory by replacing the cushion pressure with the pressure patch moving uniformly with an oscillating strength. And the bag-finger skirt is assumed to be deformed due to the pressure disturbance while its surface area remained constant. The restoring force and moment due to the deformation of bag-finger skirt from the equilibrium shape is included in the equations of hearse and pitch motions. The numerical results of motion responses due to various ratios of the bag and cushion pressure or bag-to-finger depth ratios are shown.
A Stochastic Prediction of Rolling of Ships Using Equivalent Non-linear Method
Sun-Hong Kwon ; Jung-Han Chung ; Dae-Woong Kim ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 60~65
The roll response of a ship to random beam seas is investigated in terms of the threshold crossing process. The non-white excitation process is modeled as an equivalent white-noise one based on the assumption that the upcrossing properties of the response can be approximately replaced by the excitation with a white noise process with a suitable intensity. Then the non-linear damping is reinstated. The reinstated equation of motion with the equivalent white-noise intensity is solved using the equivalent non-linear method to get the desired probability density function. The proposed scheme is tested extensively with varing coefficients.
A Computational Method of Wave Resistance of Ships in Water of Finite Depth
S.J. Lee ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 66~72
A computational method of the Michell integral for water of finite depth is developed and the method makes use of the expansion of the hull form by the Legendre polynomial in both the longitudinal and the vertical directions. The wave resistance coefficient is given as a quadruple summation of the product of the shape factor and the hydrodynamic factor. The shape factor depends only upon the geometry of the hull form, and the hydrodynamic factor upon the depth-based Froude number and the ratios of the water depth and the draft to the ship length. Example calculations are done for the Wigley parabolic hull and the Series 60
0.6, and the comparison of our results with the existing experimental data is shown.
A Simple Analysis to Obtain a Singularity near a Crack Perpendicular to Bimaterial Interface by Using 8-node Isoparametric Element
Won-Kyun Lim ; Sang-Chul Kim ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 73~78
Numerical method by Abdi et al. for obtaining a stress singularity near a crack perpendicular to the interface between two elastic materials is reviewed. More efficient and simple method to obtain crack singularity by shifting a mid-side node of 8-node isoparametric element is presented. It is observed that the present analysis provides increased accuracy for the expression of the opening displacement and the determination of the optimal position of the mid-side node for a wide range of material properties.
A Study on Patch Design Technique for Fatigue Life Prolongation of Cracked Structures
M.S. Han ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 79~91
This paper develops the compliance approach to the problem of load sharing between a cracked plate and a patch used to bridge the crack. The theory is validated by using calculated stress intensity factors for the patched and unpatched case to reduce experimentally observed growth rates to common base, Calculations are then made on the effect of patch dimension on fatique life technique. The optimum design of the patch considered the life expectancy and fracture strength of the cracked structure can be performed simply by using this technique.
Prediction of Ships' Bow Structural Damage during Collisions
P.D.C. Yang ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 92~102
Prediction of energy absorption for bow structure is important for a design of protective structures against collision. For the crushing behaviour of basic element of energy absorption, the plastic mechanism method is applied. The ship's crushing strength of bow section is obtained by summing the energy dissipated in all individual elements. The theoretical predictions are compared with experimental results for ship's bow models published with experimental results for ship's bow models published in the references, and it is observed that the present prediction method of crushing strength correlates well with the experimental results.
Elastic Buckling Reliability Analysis of Circular Cylindrical Shell with Random Geometric Initial Imperfection
Y.S. Yang ; D.K. Kim ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 103~114
A study result of buckling reliability is presented for the axially compressed imperfect elastic cylinder. Multi-mode analysis program is developed from Karman-Donnell Equation for the calculation of the buckling load of the cylindrical she1l. Geometric intial imperfection is approximated by double Fourier series of which coefficients are assumed random variables with jointly normal distribution characteristics. Crude Monte Carlo simulation technique is used to calculate the probabilistic failure properties of several cases with various imperfection Conditions.
An Optimum Design of Sandwich Panel at Fixed Edges
K.S. Kim ; I.T. Kim ; Y.Y. Kim ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 115~122
A sandwich element is a special Hybrid structural form of the composite construction, which is consisted of three main parts : thin, stiff and relatively high density faces separated by a thick, light, and weaker core material. In a sandwich construction, the shear deformation of the faces. Therefore, in the calculation of the bending stiffness, the shear effect should be included. In this paper, the minimum weight is selected as an object function, as the weight critical structures are usually composed of these kind of construction. To obtain the minimum weight of sandwich panel, the principle of minimum potential energy is used and as for the design constraints, the allowable bending stress of face material, the allowable shear stress of core material, the allowable value of panel deflection and the wrinkling stress of faces are adopted, as well as the different boundary conditions. For the engineering purpose of sandwich panel design, the results are tabulated, which are calculated by using the nonlinear optimization technique SUMT.
Static Redesign Techniques for Ship Structures
O.H. Kim ; J.W. Park ; S.R. Cho ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 123~131
In ship structural design procedures structural analyses are performed using the scantlings of structural elements determined at the initial design stage based on relevent rules and previous experiences. Modifications of scantlings will be carried out in case that the analysis results do nut satisfy design criteria. Reanalysis method s are efficient to analyse the structures of slightly modified using information obtained from the previous analysis. In this paper various approximate reanalysis techniques will be compared and their characteristics will be described. Furthermore sensitivity analyses are adapted to provide information from which selection of most influential design variables will be made and amount of modification can be determined. Redesign procedures described herein are demonstrated using examples.
A Geometrically Nonlinear Analysis of the Curved Shell Considering Large Displacements and Large Rotation Increments
Jae-Wook Lee ; Young-Tae Yang ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 132~139
This paper presents geometrically nonlinear formulation of shell problems using the three-dimensional curved shell element, which includs large displacements and large rotations. Formulations of the geometrically nonlinear problems can be derived in a variety of ways, but most of them have been obtained by assuming that nodal rotations are small. Hence, the tangent stiffness matrix is derived under the assumptions that rotational increments are infinitesimal and the effect of finite rotational increments have to be considered during the equilibrium iterations. To study the large displacement and large rotation problems, the restrictions are removed and the formulations of the curved shell element including the effect of large rotational increments are developed in this paper. The displacement based finite element method using this improved formulation are applied to the analyses of the geometrically nonlinear behaviors of the single and double curved shells, which are compared with the results by others.
Eigensensitivity Synthesis and Its Applications
Joo-Ho Heo ;
Journal of the Society of Naval Architects of Korea, volume 29, issue 2, 1992, Pages 140~149
The new method, termed the substructural eigensensitivity synthesis method, utilizes the computational merits of the component mode synthesis technique and of sensitivity analysis for the design sensitivities of the dynamic characteristics of substructurally combined structures. It is shown that the eigensensitivities of the entire structure can be obtained by synthesizing the substructural eigensolution and the sensitivities of the eigensolution for the design variables of the modifiable substructure. The sensitivities of the eigenvalues and eigenvectors obtained by the new method are compared to exact eigensolutions in terms of accuracy and computational efficiency. The small errors in eigensensitivity due to the truncation of higher modes remain within a manageable and permissible range for further analysis. The advantage of the newly proposed method as compared to the direct application of sensitivity analysis of the whole structure is demonstrated through examples.