• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.100-108
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• 2016

A high-pressure ball valve was developed, and both the structural strength and sealing performance were assessed based on a nonlinear finite element analysis. Different parts were modeled with solid elements and assembled, taking into account both contact and sliding effects. Three different loading scenarios were analyzed, including a high-pressure closure test and fire and shell test conditions. The structural safety of each part was checked under each loading condition, and the sealing performance was also investigated to validate the performance of the valve.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.4
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• pp.217-222
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• 2010

Since 1980's, optimum design techniques for ship structural design have been developed to the preliminary design which aims at minimum weight or minimum cost design of mid-ship section based on analytic structural analysis. But the optimum structural design researches about the application for the detail design of local structure based on FEA have been still insufficient. This paper presents optimization technique for the detail design of a racing motor boat. To improve the performance and reduce the damage of a real existing racing boat, direct structural analyses; static and non-linear transient dynamic analyses, were carried out to check the constraints of minimum weight design. As a result, it is shown that the optimum structural design of a racing boat has to be focused on reducing impulse response from pitching motion than static response because the dynamic effect is more dominant. Optimum design algorithm based on nonlinear finite element analysis for a racing motor boat was developed and coded to ANSYS, and its applicability for actual structural design was verifed.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.2
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• pp.87-95
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• 2010

The structural intensity analysis, which calculates the magnitude and direction of vibrational energy flow from vibratory velocity and internal force at any point of a structure, can give information on dominant transmission paths, positions of sources and sinks of vibration energy. This paper presents a numerical simulation system for structural intensity analysis and visualization to apply for ship structures based on the finite element method. The system consists of a general purpose finite element analysis program MSC/Nastran, its pre- and post-processors and an in-house program module to calculate structural intensity using the model data and its forced vibration analysis results. Using the system, the structural intensity analysis for a 4,100 TEU container carrier is carried out to visualize structural intensity fields on the global ship structure and to investigate dominant energy flow paths from harmonic excitation sources to superstructure at resonant hull girder and superstructure modes.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.790-796
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• 2003

As a fluid machinery for piping liquid in the reactor cooling system, multi-stage centrifugal pump requires the structural dynamic stability against external dynamic excitation. This paper is concerned with the finite element analysis of its eigen behavior and seismic response to RRS(Required Response Spectrum) curves in the case of SSE (Safe Shutdown Earthquake). Through the finite element analysis, the major vibration characteristics of multi-stage centrifugal pump(MSCP) are investigated and seismic qualification based on the IEEE codes is executed. The numerical results show that the MSCP used in this study has enough seismic strength.

• Journal of Ship and Ocean Technology
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• v.12 no.2
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• pp.1-15
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• 2008

The main idea of this paper introduce stochastic structural parameters and random dynamic excitation directly into the dynamic functional variational formulations, and developed the nonlinear dynamic analysis of a stochastic variational principle and the corresponding stochastic finite element method via the weighted residual method and the small parameter perturbation technique. An interpolation method was adopted, which is based on representing the random field in terms of an interpolation rule involving a set of deterministic shape functions. Direct integration Wilson-${\theta}$ Method was adopted to solve finite element equations. Numerical examples are compared with Monte-Carlo simulation method to show that the approaches proposed herein are accurate and effective for the nonlinear dynamic analysis of structures with random parameters.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.4
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• pp.328-335
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• 2023

In this paper, among the various facilities used in marine farming, young bivalves of the Mytilus galloprovincialis of marine farming was placed on the deck of the fishing vessel to evaluate the environment conditions and drive shaft movement by rolling affecting the separator for the young bivalves and a clean process. There were a few studies on stress analysis of development facilities because it was difficult to access the fishing site due to the use of imported equipment and the lack of development of domestic equipment. In this study, stress analysis of the fixed part of separator for young bivalves and its adjacent part was performed on various phases when the vessel was tilted by rolling using the finite element method. In addition, the structural safety of the internal blade under the driving conditions according to the movement of the drive shaft by the hydraulic motor was confirmed through structural analysis. As a result, the connection part between the deck and the separator by rolling was confirmed to have higher stress than that of other parts due to stress concentration. In addition, it was confirmed that the maximum stress occurred on the connection part between blades. Even though the safety of the separator for marine farming was confirmed by structural analysis, it is necessary to comprehensively consider the age of vessels, the material of the deck, and the corrosion of the deck.

• Journal of the Korean institute of surface engineering
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• v.49 no.4
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• pp.344-348
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• 2016

Stainless steel is widely applied in many industrial fields due to its excellent anti-corrosion and durability characteristics. However, stainless steel is very vulnerable to cavitation attack caused by high speed flow of fluid in the chloride environments such as marine environment. These conditions promote intergranular corrosion and cavitation-erosion, leading to degradation of the structural integrity and service life. In order to prevent these problems, the stabilized stainless steel is applied to the offshore and shipbuilding industries. In this study, Ti was added to 19%Cr-9%Ni as the stabilizer element with different concentrations (0.26%, 0.71%), and their durabilities were evaluated with cavitation-erosion experiment by a modified ASTM G32 method. The microstructural change was observed with the stabilizer element contents. The result of the observation indicated that the amount of carbide precipitation was decreased and its size became finer with increasing Ti content. In the cavitation-erosion experiment, both weight loss and surface damage depth represented an inverse proportional relationship with the amount of Ti element. Consequently, the stainless steel containing 0.71% of Ti had excellent durability characteristics.

• Journal of Navigation and Port Research
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• v.33 no.9
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• pp.635-644
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• 2009

The optimum design of power yacht belongs to the nonlinear constrained optimization problems. The determination of scantlings for the bow structure is a very important issue with in the whole structural design process. The derived design results are obtained by the use of real-coded micro-genetic algorithm including evaluation from Lloyd's Register small craft guideline, so that the nominal limiting stress requirement can be satisfied. In this study, the minimum volume design of bow structure on the power yacht was carried out based on the finite element analysis. The target model for optimum design and local structural analysis is the bow structure of a power yacht. The volume of bow structure and the main dimensions of structural members are chosen as an objective function and design variable, respectively. During optimization procedure, finite element analysis was performed to determine the constraint parameters at each iteration step of the optimization loop. optimization results were compared with a pre-existing design and it was possible to reduce approximately 19 percents of the total steel volume of bow structure from the previous design for the power yacht.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1222-1230
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• 2022

The rotor blade is an important component of a tidal stream turbine and is affected by a large thrust force and load due to the high density of seawater. Therefore, the performance must be secured through the geometrical and structural design of the blade and the blade structural safety to which the composite material is applied. In this study, a 1 MW class large turbine blade was designed using the blade element momentum (BEM) theory. GFRP is a fiber-reinforced plastic used for turbine blade materials. A sandwich structure was applied with CFRP to lay-up the blade cross-section. In addition, to evaluate structural safety according to flow variations, static load analysis within the linear elasticity range was performed using the fluid-structure interactive (FSI) method. Structural safety was evaluated by analyzing tip deflection, strain, and failure index of the blade due to bending moment. As a result, Model-B was able to reduce blade tip deflection and weight. In addition, safety could be secured by indicating that the failure index, inverse reserve factor (IRF), was 1 or less in all load ranges excluding 3.0*Vr of Model-A. In the future, structural safety will be evaluated by applying various failure theories and redesigning the laminated pattern as well as the change of blade material.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.604-610
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• 2018

Recently, due to the rapid growth of the leisure industry, demand for small-scale flotation and mooring pontoon platforms has been increasing rapidly. Standard rules for the design and structural safety of such structures have become necessary. This paper provides criteria that can be referenced when designing pontoon platforms, and also introduces structural safety evaluation procedures. In this study, the structural safety and stability of a 15-meter pontoon platform were investigated through structural design and finite element analysis. For platforms of less than 10 meters in length, a simple structural calculation can be used, but for platforms over 10 meters, a detailed structural strength review must be considered to meet safety guidelines defined in existing regulations. The structural strength of the initial design was examined and its structural safety was verified. For future research, it is an evaluative system was developed that can be used to examine the various loading conditions during design.