Cheol-Ho Ryu

Transformation of a thin-walled solid model into a surface model via solid deflation

A simplified geometric model with lower dimensionality, such as a mid-surface model, is often preferred over a detailed solid model for the analysis process, if the analysis results are not seriously impacted. In order to derive a mid-surface model from a thin-walled solid model, in this paper, we propose a novel approach called the solid deflation method. In this method, a solid model is assumed to be created by using air to inflate a shell that comprises the surface of the solid model. First, the model is simplified by the removal of any detailed features whose absence would not alter its overall shape. Next, the solid model itself can be converted into a degenerate solid model with zero thickness. Finally, a surface model is generated by splitting large faces paired in the thinned solid model, selecting one face per pair for creating a sheet model, and sewing the selected faces. Using this method, a more practical and usable mid-surface model can be very efficiently generated from a solid model because it can circumvent not only the tedious trimming and extension processes of the medial axis transformation method but also the time-consuming patch joining process of the mid-surface abstraction approach.

Development of simulation-based production execution system in a shipyard: a case study for a panel block assembly shop

The management of a panel block shop in a shipyard is a complex process that entails the largest amount of work and in which many decisions are involved. Shipbuilders have considered the process as a bottleneck since every panel for every ship must be processed through the shop. The objective of this research is to carry out a materials flow analysis to maximise process productivity and to place simulation optimisation technology in the hands of decision makers, such as production planners and supervisors. In this article, a production execution planning system is proposed for panel block operations utilising discrete-event simulation and simulated annealing. The simulation model was validated using a real production scenario and the comparison showed a very favourable agreement between the actual panel shop and the simulation model. The proposed system supports production planners by general dispatching rules and optimisation to make better scheduling decisions on the shop floor. The system will provide a complete schedule that is at least as clear and accurate as any schedule currently obtained.

Heuristic and metaheuristic spatial planning of assembly blocks with process schedules in an assembly shop using differential evolution

It is important to accurately and efficiently schedule work-in-process at this time as the shipbuilding industry is expanding. The availability and load of workshops or factories should be necessarily examined in scheduling the work-in-process. A space planning and scheduling system has been implemented as a result of our previous research. The system can be used in planning arrangement of ship blocks into the work plates. In this article, a heuristic arrangement algorithm is implemented to automatically arrange the blocks by extending the previous system. A block allocation policy is defined to determine the allocation orders on a basis of bottom-left-fill heuristic method. To improve accuracy and efficiency of block arrangement, a metaheuristic placement method is formulated as a combinatorial optimisation problem for the allocation sequence and orientations of blocks. It is solved with differential evolution. The heuristic and metaheuristiic spatial planning is carried out with real geometric data and schedule of ship blocks.

Developable polynomial surface approximation to smooth surfaces for fabrication parameters of a large curved shell plate by Differential Evolution

This paper presents a simple and efficient method to approximate a developable surface to a compound design surface by a polynomial. It is required to predict a final shape of roll bending in the fabrication of a curved shell plate. The roll bending process usually makes the cylindrical or conical curvature from an initial flat plate. It means that the final shape is developable or the surface representation has zero Gaussian curvature. The fabrication shape is important in order to estimate process parameters of roller bending. An optimization problem is formulated to determine the polynomial surface which is in the closest proximity to the design surface or the given shell plate, which is subjected to developability. The results and the efficiency of this algorithm are verified and evaluated by applying it to some shell plates which are obtained from a real ship model. The predicted bending shape becomes fundamental information in determining more process parameters for the fabrication of a compound curved shell plate.

Development of integrated and interactive spatial planning system of assembly blocks in shipbuilding

As the shipbuilding industry expands, accurate and efficient planning and scheduling of the production process is becoming increasingly important and complex. The availability of space and load in workshops should thus be examined in scheduling the production process. The variety of material, facilities, and information resources makes the spatial planning difficult. In the present work, a spatial planning and scheduling system is developed to support spatial planning and scheduling in block assembly shops, and the workload balance of workshops. The requirements and functions of the system are described and functional components are designed and implemented, based on an object-oriented methodology. The integrated environment is presented in this paper. This system can be expanded to any workshop that requires spatial planning and scheduling.

A Study on Discrete Event Simulation of Shipyard Outdoor Block Movement

a , 이장현 ** , 우종훈 * b , 신종계 *** , 유철호 †** Abstract Simulation model of outdoor block movement of shipyard is implemented in this paper. The load of the outdoor workshops in a shipyard influences a mid-term planning and scheduling of the shipyard. Since the load analysis is expected in advance before confirming the planning and scheduling, a discrete event simulation (DES) may be a good solution. The accuracy of DES is up to the accurate modeling of Products, Processes, and Resources (PPR) included in a system. PPR in the outdoor system are clearly defined and the simulation model for the outdoor logistics is implemented by modeling the selective PPR with the help of a DES tool which is programmable by users. The simulation model is verified by comparing the results with the real shipyard data. The outputs through the simulation are discussed.

Flaw Assessment on an Offshore Structure using Engineering Criticality Analysis

조선해양산업의 차세대 성장동력으로서 해양플랜트가 주목 받 고 있다. 심해 자원을 채굴하는 해양플랜트산업은 이전보다 고도 의 기술력이 요구되며 심해 자원의 경제성이 완전히 소모될 때까 지 해양플랜트 설비가 안정적으로 운영되어야 하는 특성이 있다. 해양구조물의 극후판으로 구성되는 구조부재의 경우 용접으로 연결되어 있기 때문에 미세한 초기결함이 존재할 가능성이 크다. 비파괴 검사 과정 중에 구조부재에 초기결함이 발견 된다면 지속 적인 파랑하중으로 유기되는 반복 하중을 받아 초기결함이 진전 하면서 해양구조물은 피로파괴에 상당히 취약할 수 있다. 따라서 주어진 피로 하중 수명 동안 해양 구조물이 구조적으로 안전한 지에 대한 평가 해석이 필요하며 이를 테면 용접 부나 구조적 취 약부에 존재하는 초기결함의 정보를 이용한 파괴역학 기반의 결 함 평가 해석이 수행되어야 한다. 파괴역학 기법을 이용한 피로 수명 예측 및 구조 안전성 평가 를 위한 연구가 국내에서 활발히 이루어졌다. Noh, et al. (1993) 는 독립형 LNG탱크의 총체적인 구조안전성 평가과정을 다뤘다. 파랑 응력의 장기분포 해석을 수행하여 S-N선도를 이용한 피로 강도 평가를 실시하였고 LBF(Leak Before Failure)이론을 바탕으 로 관통균열의 진전해석을 수행하여 급속 취성파괴에 대한 안전 성을 검증하였다. Yim and Byun (1993)은 BSI PD 6493의 3단 계 평가방법에 균열 성장 효과를 고려한 건전성 평가 방법과 균 열의 안정성장을 엄밀히 고려할 수 있는 안정성 평가방법 (Stability Assessment Method: SAM)과 더불어 소성붕괴를 평가 하는 극한 하중해석을 고려한 건전성 평가방법을 정식화 하였다. Jeon, et al. (2001)은 선체 구조에서 피로손상을 받기 쉬운 용접 부위인 T형 이음부 및 호퍼 너클 이음부 모델의 피로실험 및 선 형탄성 파괴역학을 이용한 피로균열 진전해석을 수행하여 피로 균열 진전 수명을 정확히 예측하였다. Kim, et al. (2002)은 구조 pISSN:1225-1143, Vol. 52, No. 6, pp. 435-443, December 2015

Development of Shipbuilding Execution Scheduling Support System using Mobile Device : A Case Study for a Panel Block Assembly Shop

Owing to the development of mobile communication technology during the last a few years, the number of users of mobile devices such as the smartphone and the tablet PC has increased rapidly. As a result, the range of applications of the mobile devices has also been greatly expanded from an application for the convenience of daily life to an application for assisting the operations of industrial fields. Especially, portability of mobile devices can provide great help in collecting and using information on the production site. In shipbuilding production processes, it is difficult to collect changes of circumstance in the field and reflect the changes to schedule due to the low production automation rate and frequent changes in schedule. In this study, we propose a system to solve the problems of shipbuilding production processes such as the ones described above by using mobile devices. First of all, we organize the production information and production processes of the panel line through the analysis of shipyard panel line operations. Next, we have developed a system that can support the production execution plan of the panel line and monitor the production processes in the field. The system was developed utilizing application virtualization to allow access to the system from various platforms of mobile devices and PC`s. The system was implemented using ooCBD methodology considering the future expansion of the system and ease of maintenance.

Design and Development of Scenario-Based Simulation System to Improve Shipbuilding Execution Scheduling Assessment -A Case Study on Panel Line-

Today`s ever-increasingly competitive shipbuilding market makes it essential for a shipbuilding company to have more efficient production processes and higher productivity as well as better design ability to obtain its competitiveness. A well-established production execution schedule plays an indispensable role to achieve this goal. Most shipbuilding companies carry out an evaluation on their mid-term plan once it is established. However, no evaluation activity exists for a production execution schedule, because practically all the companies depend on the field workers for the production execution scheduling. In this study, a prototype of a ship production execution schedule evaluation system is developed based on the component based design (CBD) methodology. This system enables one to make a production execution schedule that reflects up-to-date shipyard situation and to validate whether the schedule is feasible or not by running a production simulation according to the schedule. Users can also make use of the system as a decision supporting tool that compares several different execution schedules and evaluates which one is the best execution schedule.

A Study on the Quality Management System for Smart Shipyard Based on Mobile

In the smart life era where the majority of economically active population uses mobile devices, smart devices have formed a new service market. In this study, we developed a shipyard quality management application using mobile devices such as smart phones and tablet PCs. For this purpose, the problems were derived through the analysis of the quality management work on shipyard and the considerations were extracted to build a smart work environment by analyzing the case studies of smart work in other industrial fields. Among the shipyard quality management work, functions thought to be highly utilized when converted to a mobile system has been developed as a mobile application. The application was developed by applying an object-oriented component-based development (ooCBD) methodology, and is expected to improve the user experience and the efficiency of quality management operations in shipyard.