Dae-Eun Ko

Development of the Weight Reduction Program for Corrugated Bulkheads of a Product Oil Carrier

AbstractFor a Product Oil Carrier, longitudinal bulkhead as well as tra nsverse one is corrugated shape in general and intersection part of bulkheads is utilized for a pipe trunk. Since lower and upper stools are to be connected with all of longitudinal a nd transverse bulkheads, they have a uniform height respectively. The purpose of this study i s the development of design system for the minimization of total weight of longitudinal and transverse bulkheads at the initial design stage. In this study, the beam element models fo r longitudinal and transverse corrugated bulkheads are established and they are applied to th e structural analysis. For the practical design, the selection and the position of an addition al pipe trunk are considered in this study. In addition the required minimum distance between t he bracket installed along the web of corrugation at lower stool and the diaphragm is taken into consideration during optimization process. Evolution strategy(ES) is adopted as an o ptimization technique.

Overlap-Avoidance Algorithm for Automation of Drawing Generation

** Abstract This paper deals with the automation techniques of ship assembly drawing generation, which help the designer to reduce the man-hour for completing the drawings, and improve the quality of the drawing for the given time. The automation techniques are necessary for the reasons of economical efficiency and improve communication between the designers and shop-makers. The overlap-avoidance algorithm of this paper maximizes the readability of the drawings using the optimization techniques a nd the heuristic rules, especially for the ship assembly field.

A Study on the Hole-Plan system combined with 3D CAD

It is necessary to construct the process automation system to improve the design efficiency and procure the higher design quality on the field of ship building. To construct this system, the shipbuilding companies should improve the 3D CAD/CAM system customized to the ship design and the software about design information management which could solve the conflict problem between the several related design division at the same time. The typical example is the Hole-plan process in the ship-building design. For the request of additional holes from outfitting division, the hull design division checks the compatibility conditions and reflects these holes to the hull panels if acceptable. if not, the requests are rejected and sent back to the outfitting division. These serial processes are not simple and require the tedious communication, discussion, and the complicated drawings. This article gives a basic introduction to the process of hole-plan system and proposes a strategy to automate its process.

Dynamic Pressure Distribution due to Horizontal Acceleration in Spherical LNG Tank with Cylindrical Central Part

Spherical LNG tanks having many advantages such as structural safety are used as a cargo containment system of LNG carriers. However, it is practically difficult to fabricate perfectly spherical tanks of different sizes in the yard. The most effective method of manufacturing LNG tanks of various capacities is to insert a cylindrical part at the center of existing spherical tanks. While a simplified high-precision analysis method for the initial design of the spherical tanks has been developed for both static and dynamic loads, in the case of spherical tanks with a cylindrical central part, the analysis method available only considers static loads. The purpose of the present study is to derive the dynamic pressure distribution due to horizontal acceleration, which is essential for developing an analysis method that considers dynamic loads as well.

A Study on the Characteristics of Design Variables for IRSS Diffuser

In modern naval ships, infrared signature suppression systems (IRSS) are installed to decrease the temperature of waste gas generated in propulsion engine and the metallic surface temperature of heated exhaust pipes. Generally, IRSS is composed of eductor, mixing tube, and diffuser. Diffuser serves to reduce the temperature by creating an air film using the pressure difference between internal gas and external air. In this study, design variables were selected by analyzing the diffuser and the characteristics of design variables that affect the performance of diffuser were examined using Taguchi experiment method. For the diffuser performance analysis, a heat flow analysis technique established in previous research was used. The IRSS performance evaluation was carried out based on the average area value of the metal surface temperature and the temperature of the exhaust gas at the outlet of the diffuser, which are variables directly related to the intensity of infrared signature in naval ships. It was verified that the exhaust gas temperature is greatly affected by changes in the diameter of the diffuser outlet, and the metal surface temperature of diffuser is greatly affected by changes in the number of diffuser rings.

A Study on the Optimum Design of Corrugated Bulkhead for Product Carrier

For a product carrier, in general, longitudinal bulkhead as well as transverse bulkhead is corrugated type and the intersection part of bulkheads is utilized for a pipe trunk. Since lower and upper stools are to be connected with all of longitudinal and transverse bulkheads, they have a uniform height respectively. The purpose of this study is the development of design technique for the minimization of total weight of longitudinal and transverse bulkheads at the initial design stage. In this study, optimum design of corrugated bulkhead for product carrier was conducted by applying evolution strategy method (ESM) as an optimization method and beam elements based on generalized slope deflection method (GSDM) in structural analysis. Furthermore, the installations of pipe trunks and the interference of stool diaphragms and brackets were considered to conform to the actual ship design. The optimization results are compared with the existing 70K product carrier designed in accordance with the DNV classification requirements and showed about 3% reduction in weight.

A Study on the Conceptual Design of Quay Process Monitoring System

In quay processes in shipyards, it is difficult to manage workers and to maintain secure working environments because at least 1,000 people can occupy the quay at the same time. In this study, a system was designed to monitor the environment and processes of quay operation. In order to lower initial investments and the costs of maintenance and operation, the entire system consists of six connected components. Considering the communication environment of the shipyard site, Wi-Fi and the LoRa communication protocol were selected for the system. The feasibility of the communication protocols was verified by data transmission tests in the field. The designed system can provide real-time information about employees working in the quay area, the safety status of moored ships on the quay, and step-by-step alarms in dangerous situations based on the detected information. The system is expected to prevent or greatly reduce safety hazards.

A Study on Minimum Weight Design of Horizontal Corrugated Bulkheads for Chemical Tankers

Corrugated bulkheads have many advantages compared to stiffened bulkheads, and they have thus been used for the cargo tank bulkheads of commercial vessels, such as bulk carriers, product oil carriers, and chemical tankers. Various studies have been carried out to find the optimum corrugation shape for bulk carriers, but optimum design studies for chemical tankers with bulkheads made of high-priced materials are scarce. The purpose of this study is to develop a minimum weight design method for horizontal corrugated bulkheads for a chemical tanker. An evolution strategy (ES) that searches for a reliable global optimum point was applied as an optimization technique, and the structural safety of the optimum design was verified through structural analysis using the finite element method (FEM). The results were compared with those of an existing ship, which showed a weight reduction of about 14% with equivalent structural strength.

Development of Equations for Static Design Loads of Sphere Type LNG Tank with Cylindrical Extension

The number of shop needed for the fabrication of sphere type LNG tank is proportional to that of the tank radius to be constructed. Due to limitation of facility investment including building sites, it is practically difficult to fabricate various size tanks of perfectly spherical shape in the yards. The efficient method to increase cargo tank capacity is to extend vertically the conventional sphere type LNG tank by inserting a cylindrical shell structure. In this study, equations for static design loads are developed for sphere type LNG tank with central extension. The results of this study will be combined with dynamic design loads to build the simplified analysis method which enable the precise initial estimate instead of time consuming finite element analysis.

Simulation of Curved Surface Forming of Steel Plate by Induction Heating

Abstract Ship hull is a compound curved shape and most of shipyards have been using gas heating method for thesurface forming of steel plate. This traditional forming process have problems such as difficulties in heat input controland poor working conditions due to loud noise and air contamination. Recently, researches on automatic hull formingsystem have been conducted using high frequency induction heating method which have good control ability and favorable working environment. In this study, the induction heating simulation system for curved surface forming of steel plate was developed and induction heating experiments were performed. Based on the results of this study, efficient induction heating coil design and optimal heating conditions for the automatic hull forming system can be obtained. Keywords : High frequency induction heating, Simulation, Automatic hull forming system 이 논문은 2015학년도 동의대학교 연구년 지원에 의하여 연구되었음. * Corresponding Author : Dae-Eun Ko(Dong-Eui Univ.)Tel: +82-51-890-2594 email: deko@deu.ac.krReceived March 25, 2015 Revised April 24, 2015Accepted July 16, 2015 Published July 31, 2015