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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 53, Issue 5 - Oct 2016
Volume 53, Issue 4 - Aug 2016
Volume 53, Issue 3 - Jun 2016
Volume 53, Issue 2 - Apr 2016
Volume 53, Issue 1 - Feb 2016
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Analysis Method of Ice Load and Ship Structural Response due to Collision of Ice Bergy Bit and Level Ice
Nho, In Sik ; Lee, Jae-Man ; Oh, Young-Taek ; Kim, Sung-Chan ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 85~91
DOI : 10.3744/SNAK.2016.53.2.85
The most important factor in the structural design of ships and offshore structures operating in arctic region is ice load, which results from ice-structure interaction during the ice collision process. The mechanical properties of ice related to strength and failure, however, show very complicated aspect varying with temperature, volume fraction of brine, grain size, strain rate and etc. So it is nearly impossible to establish a perfect material model of ice satisfying all the mechanical characteristics completely. Therefore, in general, ice collision analysis was carried out by relatively simple material models considering only specific aspects of mechanical characteristics of ice and it would be the most significant cause of inevitable errors in the analysis. Especially, it is well-known that the most distinctive mechanical property of ice is high dependency on strain rate. Ice shows brittle attribute in higher strain rate while it becomes ductile in lower strain rate range. In this study, the simulation method of ice collision to ship hull using the nonlinear dynamic FE analysis was dealt with. To consider the strain rate effects of ice during ice-structural interaction, strain rate dependent constitutive model in which yield stress and hardening behaviors vary with strain rate was adopted. To reduce the huge amount of computing time, the modeling range of ice and ship structure were restricted to the confined region of interest. Under the various scenario of ice-ship hull collision, the structural behavior of hull panels and failure modes of ice were examined by nonlinear FE analysis technique.
An Estimation of the Size of Supercavities for Conical Cavitators
Kim, Hyoung-Tae ; Kim, Byeung-jin ; Choi, Jung-Kyu ; Yoon, Hyun-Gull ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 92~100
DOI : 10.3744/SNAK.2016.53.2.92
A comparative method is applied to evaluate well-known formulas for estimating the size of supercavities of axisymmetric cavitators for the supercavitating underwater vehicle. Basic functional forms of these formulas are derived first for the cavity diameter from a momentum integral estimate and second for the cavity length from an asymptotic analysis of inviscid supercavity flows. The length and the diameter of axisymmetric supercavities estimated by each formula are compared, with available experimental data for a disk and a 45° conical cavitators, and also with computational results obtained by a CFD code, ‘fluent’, for conical cavitators of wide range of cone angles. Results for estimating the length and the diameter of the supercavities show in general a good agreement, which confirms the size of the supercavities for disk and conical cavitators can be estimated accurately by these simple formulas of an elementary function of cavitation number and drag coefficient of the cavitator. These formulas will be useful for from conceptual design of the cavitator to real-time control of the supercavitating underwater vehicle.
A Study on the Erection Process Modeling and Simulation considering Variability
Lim, Hyunkyu ; Lee, Yonggil ; Kim, Byungchul ; Woo, Jonghun ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 101~107
DOI : 10.3744/SNAK.2016.53.2.101
Generally, the shipbuilding industry has finite resources and limited workspace. Due to finite resources, limited workspace and state of block preparation, erection process in shipbuilding industry is frequently delayed than erection process scheduling which is planned at long-term plan stage. In this study, considering variability of block reserve ratio, the degree of delay in real erection process is measured and compared to scheduling which is planned at long-term plan stage in shipbuilding industry including finite capacity and variative lead time. Also, the erection process scheduling which has minimum lead time can be checked through simulation. The results of this study could be improved the accuracy of erection process scheduling by checking the main event compliance ratio by block reserve ratio and calculating the optimum erection pitch for the main event compliance.
Structural Strength Assessment and Optimization for 20 Feet Class Power Boat
Yum, Jae-Seon ; Yoo, Jaehoon ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 108~114
DOI : 10.3744/SNAK.2016.53.2.108
Recently, there has been a growing interest in marine leisure sports and high speed power boat for fishing. The prototype of 20 feet class power boat was developed and authors are joined in this government-led project. The research was performed to evaluate the optimal structure and design of the structural strength necessary to ensure the structural safety of the power boat. A new material ROCICORE fiber added to the mat and roving was adopted for high-power tenacity. ANSYS Workbench has been used to make the structural model, evaluate the strength and optimize the structural design. The response of the structure to quasi-static slamming loads according to the rules and regulations of ISO 12215-5, Lloyd’s Register of Shipping and Korean Register has been implemented and studied. An optimization study for the structural response is carried out by changing the plate thickness and section modulus of stiffeners. The power boat structure derived fuel efficiency is optimized by performing the best possible structural design to minimize the hull weight.
Comparison of Optimal Path Algorithms and Implementation of Block Transporter Planning System
Moon, Jong-Heon ; Ruy, Won-Sun ; Cha, Ju-Hwan ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 115~126
DOI : 10.3744/SNAK.2016.53.2.115
In the process of ship building, it is known that the maintenance of working period and saving cost are one of the important part during the logistics of blocks transportation. Precise operational planning inside the shipyard plays a big role for a smooth transportation of blocks. But many problems arise in the process of block transportation such as the inevitable road damage during the transportation of the blocks, unpredictable stockyard utilization of the road associated with a particular lot number, addition of unplanned blocks. Therefore, operational plan needs to be re-established frequently in real time for an efficient block management. In order to find the shortest path between lot numbers, there are several representative methods such as Floyd algorithm that has the characteristics of many-to-many mapping, Dijkstra algorithm that has the characteristic of one-to-many mapping, and the A* algorithm which has the one-to-one mapping, but many authors have published without the mutual comparisons of these algorithms. In this study, some appropriate comparison have been reviewed about the advantages and disadvantages of these algorithms in terms of precision and cost analysis of calculating the paths and planning system to operate the transporters. The flexible operating plan is proposed to handle a situation such as damaged path, changing process during block transportation. In addition, an operational algorithm of a vacant transporter is proposed to cover the shortest path in a minimum time considering the situation of transporter rotation for practical use.
Effective Test and Evaluation Approaches for Reliable Defense Systems Development examined through Domestic Defense Cases
Seo, Kyung-Min ; Lee, Chan Young ; Bang, Kyoung Woon ; Lee, Dong Chul ; Choi, Woo Young ; Kim, Tag Gon ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 127~134
DOI : 10.3744/SNAK.2016.53.2.127
This paper presents practical issues for test and evaluation(T&E) methods to develop defense systems. Our argument is motivated by several domestic defense cases and the cases lead us to discuss two main factors for reliable defense systems development: 1) statistical approaches and 2) technical schemes. Specifically, statistical approaches enable to provide credible interpretations about T&E results in the decision-making process. With practical T&E results of the “Red Shark” torpedo, we performed statistical hypothesis tests and suggest a minimum sample size to accept the hypothesis. Next, technical schemes have more direct effects on improving reliability of developed defense systems and we shortly introduce tools development for systems verification that is required to integrate several sub-systems, e.g., combat, sensor, weapon, and communication systems, within a defense system. We additionally summary some domain cases using modeling and simulation techniques for successful T&E. In closing, we expect that the paper shows empirical investigation and lessons learned with these two practical issues, which provides a guide those who desire to make decisions about reliable defense systems development.
Development of an Automation Library in Multi-Body Dynamics Program for Dynamic Structural Analysis of Block Lifting Process
Jung, Da-un ; Cha, Ju-Hwan ; Song, Chang-Yong ; Lee, Chung-Hyoung ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 135~143
DOI : 10.3744/SNAK.2016.53.2.135
In this study, an embedded system composed of equipment setting, block importing, scenario setting and output reporting is developed in multi-body dynamics program, ADAMS, for conducting dynamic structural analysis of block lifting process. First, equipment used for block lifting process is set in the simulation environment and the shapes and functions of two lifting beams, and six block loaders are provided as the equipment. Second, the modal analysis result of the lifting block is imported from the static structural analysis system, NASTRAN. Third, the lifting scenarios, such as hoisting, waiting, trolley moving, and wire connecting, are set in the system. Finally, output results in the forms of plots, texts and tables, are reported after the dynamic structural analysis. The test examples conducted in a shipyard are applied into the developed system in various condition and scenarios. The loads at the lug points, the stress contours, and the hot spot tables of the developed system are compared with the result of the static analysis system.
The Design, Structural Analysis and High Pressure Chamber Test of a Thick Pressure Cylinder for 2000 m Water Depth
Choi, Hyeuk-Jin ; Lee, Jae-Hwan ; Kim, Jin-Min ; Lee, Seung-Guk ; Maring, Kothilngam ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 144~153
DOI : 10.3744/SNAK.2016.53.2.144
This paper aims to demonstrate the design, structure analysis, and hydrostatic pressure test of the cylinder used in 2000m water depth. The cylinder was designed in accordance with ASME pressure vessel design rule. The 1.5 times safety factor required by the general rule was applied to the design of the cylinder, because ASME rule is so excessive that it is not proper to apply to the hydrostatic pressure test. The finite element analysis was conducted for the cylinder. The cylinder was produced according to the design. The hydrostatic pressure test was conducted at the hyperbaric chamber in KRISO. The results of finite element analysis(FEM) and those of the hydrostatic pressure test were almost the same, which showed that the design was exact and reliable.
A Preliminary Study on a Method for the Weight Estimation and Calculation of Offshore EPC Projects
Lee, Soo-Ho ; Ahn, Hyun-Sik ; Heo, Yoon ; Bae, Jae-Ryu ; Kim, Ki-Su ; Ham, Seung-Ho ; Lee, Sung-Min ; Roh, Myung-Il ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 154~161
DOI : 10.3744/SNAK.2016.53.2.154
There are several existing studies for the weight estimation of offshore plants. However, most of them were applicable at the pre-FEED (Front End Engineering Design) stage. In this paper, a preliminary study on a method for the weight estimation and calculation of offshore EPC (Engineering Procurement Construction) projects is made for the use at the estimation stage after FEED. Based on literature surveys including ISO (International Organization for Standardization) 19901-5 about weight estimation, we proposes new weight factors and a weight curve. Weight factors defined in this study include MTO (Material Take-Off), estimated weight, FEED maturity factor, allowance factor, and contingency factor. The proposed method utilizes bottom-up approach for weight estimation and it can be used for the weight estimation and calculation of offshore EPC projects at the estimation stage.
A Study on a New Concept for the Structural Strength Assessment to Development of Membrane LNG Cargo Container System under Static Load
Hwang, Se Yun ; Kim, Yooil ; Kang, Joong Kyoo ; Lee, Jang Hyun ;
Journal of the Society of Naval Architects of Korea, volume 53, issue 2, 2016, Pages 162~169
DOI : 10.3744/SNAK.2016.53.2.162
A new concept of membrane type LNG CCS was proposed. Also, its static behavior was numerically analyzed considering the interaction between primary and secondary barrier together with securing device. Hull deflection was taken into account as an external load, together with temperature distribution across the barriers. The suggested numerical model considers both sliding and contact between the two mating surfaces of both the primary and secondary barrier, and anisotropic material behavior of plywood, R-PUF was also taken into account. Furthermore, detailed local strength was evaluated for the securing device, which is arranged between two barriers to hold the primary barrier. It was confirmed through the numerical analysis that the new concept of membrane type CCS was structurally safe under static loading condition and securing concept was structurally reliable.