In shipbuilding industry, to reduce the staying time of the ship in a dock, floating crane and floating dock are used to handle the mega-blocks, thus it increased the turnover of the dock. Therefore, spatial scheduling for mega-block in an assembly yard becomes important in shipbuilding industry. However, spatial scheduling of mega-blocks has some unique characteristics compared with the well-known classic bin-packing problem, and not many studies can be found on this issue. This research proposes an enhanced mathematical formulation and a heuristic algorithm for spatial scheduling of mega-block arrangement problem. The formulation provides tight bound compared with the existing formulation, and the proposed heuristic can obtain good quality of the solution in a reasonable amount of time even when the size of the instance became large. Shipbuilding industry involves constructing ships and other floating vessels. Block is a base element of the shipbuilding process, and the blocks are assembled and welded in the block assembly shop, and finally erected to a ship in a dry dock. A size of a block is around 15~30 meters with a weight of around 30~300 tons (Zheng et al. 2011), and a large ship consists of around 150 blocks (Koh et al. 2011b). Some blocks are outsourced and timely delivery and quality of blocks have an absolute impact on the ship’s quality. Also, it is possible to shorten the dock duration by receiving blocks from several companies at the same time.
在造船业中，为了减少船舶在码头的停留时间，采用浮式起重机和浮船坞来搬运巨型块，从而增加了码头的周转量。因此，大型装配体的空间调度问题在船舶工业中具有重要意义。然而，与经典的装箱问题相比，巨型块的空间调度具有一些独特的特点，对该问题的研究并不多见。本文提出了一种改进的大块排列问题空间调度的数学公式和启发式算法。与现有公式相比，该公式具有较强的约束，即使实例规模变大，所提出的启发式算法也能在合理的时间内获得较好的解质量。造船业包括建造船舶和其他浮船。砌块是造船过程中的基本要素，砌块在砌块组装车间进行组装和焊接，最后在干船坞中竖立成船。块的大小约为15~30米，重量约为30~300吨(Zheng et al. 2011)，大型船舶由约150块组成(Koh et al. 2011b)。有些砌块是外包的，砌块的及时交付和质量对船舶质量有绝对的影响。此外，可以通过同时接收来自多个公司的区块来缩短停靠时间。
{"title":"A Mathematical Formulation and a Heuristic for the Spatial Scheduling of Mega-Blocks in Shipbuilding Industry","authors":"Namsu Ahn, S. Kim","doi":"10.5957/jspd.05200014","DOIUrl":"https://doi.org/10.5957/jspd.05200014","url":null,"abstract":"\u0000 \u0000 In shipbuilding industry, to reduce the staying time of the ship in a dock, floating crane and floating dock are used to handle the mega-blocks, thus it increased the turnover of the dock. Therefore, spatial scheduling for mega-block in an assembly yard becomes important in shipbuilding industry. However, spatial scheduling of mega-blocks has some unique characteristics compared with the well-known classic bin-packing problem, and not many studies can be found on this issue. This research proposes an enhanced mathematical formulation and a heuristic algorithm for spatial scheduling of mega-block arrangement problem. The formulation provides tight bound compared with the existing formulation, and the proposed heuristic can obtain good quality of the solution in a reasonable amount of time even when the size of the instance became large.\u0000 \u0000 \u0000 \u0000 Shipbuilding industry involves constructing ships and other floating vessels. Block is a base element of the shipbuilding process, and the blocks are assembled and welded in the block assembly shop, and finally erected to a ship in a dry dock. A size of a block is around 15~30 meters with a weight of around 30~300 tons (Zheng et al. 2011), and a large ship consists of around 150 blocks (Koh et al. 2011b). Some blocks are outsourced and timely delivery and quality of blocks have an absolute impact on the ship’s quality. Also, it is possible to shorten the dock duration by receiving blocks from several companies at the same time.\u0000","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41853261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To save costs and build competitiveness, Norwegian shipyards usually offshore some of the processes required to produce a ship, especially steel-related tasks, i.e., they have them carried out in a country with lower factor costs. This study aims to provide some quantitative evidence of the relationship between the degree of offshoring and the production time of offshore support vessels (OSVs) delivered from Norwegian shipyards. It builds upon a recent article that introduced a typology of offshoring in ship production (Semini et al. 2018, Journal of Ship Production and Design, 34(1), 59–71). We take into account contextual factors that are also expected to affect the production time of OSVs, in particular ship size and complexity, repeat production, and the global market situation. We apply multiple regression analysis on a sample of 156 OSVs delivered from nine Norwegian shipyards between 2010 and 2018. Each of these ships was, by plan and strategy, partly produced at a foreign yard, before one of the Norwegian yards took over, completed production, commissioned, tested, and finally delivered the ship. Results suggest that the higher the degree of offshoring is, the longer is the total ship production time. Only ship size explains even more of the production time variability in the sample than offshoring strategy. In addition to these two factors, evidence suggests that also repeat production and the global market situation have a significant impact on the production time. Our study contributes to the literature on the relationship between strategy and performance in shipbuilding. It provides new insights into how offshoring strategy and contextual, product- and market-related factors relate to ship production time based on quantitative, empirical evidence. From a methodological perspective, it illustrates how multiple regression analysis can be applied to ship-specific data as a benchmarking tool to measure and compare shipbuilding performance. Findings are first and foremost valid for the ships included in the study, which opens numerous opportunities for further research.
为了节省成本和建立竞争力，挪威造船厂通常将制造一艘船所需的一些工序，特别是与钢铁有关的工序，移到海外，即在一个要素成本较低的国家进行。本研究旨在提供一些量化证据，证明离岸外包程度与挪威造船厂交付的海上支援船(osv)的生产时间之间的关系。它建立在最近的一篇文章的基础上，该文章介绍了船舶生产中的离岸外包类型(semi等人，2018,Journal of ship production and Design, 34(1)， 59-71)。我们考虑了预计也会影响osv生产时间的相关因素，特别是船舶尺寸和复杂程度、重复生产以及全球市场形势。我们对2010年至2018年间从9家挪威造船厂交付的156艘osv样本进行了多元回归分析。按照计划和策略，每艘船都是在国外船厂部分生产，然后由挪威船厂接管，完成生产，调试，测试，最终交付。结果表明，船舶外包程度越高，船舶总生产时间越长。在样本中，只有船舶尺寸比离岸外包策略更能解释生产时间的变化。除了这两个因素外，有证据表明，重复生产和全球市场情况对生产时间也有重大影响。我们的研究对造船业战略与绩效之间关系的文献有贡献。它提供了新的见解离岸外包战略和上下文，产品和市场相关的因素如何与船舶生产时间基于定量的，经验的证据。从方法学的角度来看，它说明了如何将多元回归分析应用于船舶特定数据，作为衡量和比较造船性能的基准工具。研究结果首先对研究中包括的船舶有效，这为进一步研究开辟了许多机会。
{"title":"Comparing Offshore Support Vessel Production Times between Different Offshoring Strategies Practiced at Norwegian Shipyards","authors":"M. Semini, P. O. Brett, J. Strandhagen, J. Vatn","doi":"10.5957/jspd.02200005","DOIUrl":"https://doi.org/10.5957/jspd.02200005","url":null,"abstract":"To save costs and build competitiveness, Norwegian shipyards usually offshore some of the processes required to produce a ship, especially steel-related tasks, i.e., they have them carried out in a country with lower factor costs. This study aims to provide some quantitative evidence of the relationship between the degree of offshoring and the production time of offshore support vessels (OSVs) delivered from Norwegian shipyards. It builds upon a recent article that introduced a typology of offshoring in ship production (Semini et al. 2018, Journal of Ship Production and Design, 34(1), 59–71). We take into account contextual factors that are also expected to affect the production time of OSVs, in particular ship size and complexity, repeat production, and the global market situation. We apply multiple regression analysis on a sample of 156 OSVs delivered from nine Norwegian shipyards between 2010 and 2018. Each of these ships was, by plan and strategy, partly produced at a foreign yard, before one of the Norwegian yards took over, completed production, commissioned, tested, and finally delivered the ship. Results suggest that the higher the degree of offshoring is, the longer is the total ship production time. Only ship size explains even more of the production time variability in the sample than offshoring strategy. In addition to these two factors, evidence suggests that also repeat production and the global market situation have a significant impact on the production time. Our study contributes to the literature on the relationship between strategy and performance in shipbuilding. It provides new insights into how offshoring strategy and contextual, product- and market-related factors relate to ship production time based on quantitative, empirical evidence. From a methodological perspective, it illustrates how multiple regression analysis can be applied to ship-specific data as a benchmarking tool to measure and compare shipbuilding performance. Findings are first and foremost valid for the ships included in the study, which opens numerous opportunities for further research.","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46980679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. P. Vieira, Rodrigo M. Amarante, K. Y. Kang, Lariuss Zago, R. Dotta, R. S. Lavieri, C. M. Sampaio, K. Nishimoto
This article deals with the development of a numerical tool based on an integrated synthesis model to carry out the first project cycle of floating liquefied natural gas (FLNG) platforms to produce, process, store, and export liquefied natural gas (LNG). The topside configuration, tank geometry and capacity, production levels, equipment list, environmental and operating conditions, classification society requirements, structure, stability, and seakeeping are considered in a single synthesis model, generating a sufficiently large number of solutions. The case generation and the evaluation process are performed hierarchically, dividing the parameters into groups to better solve the solution space, which cannot be achieved with conventional techniques such as traditional point-based design. This methodology is applied as a case study to design three FLNG platforms with different production levels (2, 3, and 4millionmetric tons per year). Performance parameters are defined and evaluated, optimizing downtime, structural mass, and load capacity. The resulting platforms are compared to existing FLNG dimensions. Essential conclusions are drawn about design improvements, such as key dimensions, quantity, and configuration of tanks, freeboard specifications, and operating draft. The developed synthesis framework proved to be a quick and useful tool for the early stages of the FLNG project. The growing global social and demographic development has led the world to face a growing demand for energy in recent decades. Although fossil fuels are still the most widely used primary energy source, emissions of greenhouse gases and other pollutants have been a cause of concern related to the climate and the environment.
{"title":"FLNG Parametric Design: A Synthesis Modeling Approach","authors":"D. P. Vieira, Rodrigo M. Amarante, K. Y. Kang, Lariuss Zago, R. Dotta, R. S. Lavieri, C. M. Sampaio, K. Nishimoto","doi":"10.5957/jspd.02210006","DOIUrl":"https://doi.org/10.5957/jspd.02210006","url":null,"abstract":"This article deals with the development of a numerical tool based on an integrated synthesis model to carry out the first project cycle of floating liquefied natural gas (FLNG) platforms to produce, process, store, and export liquefied natural gas (LNG). The topside configuration, tank geometry and capacity, production levels, equipment list, environmental and operating conditions, classification society requirements, structure, stability, and seakeeping are considered in a single synthesis model, generating a sufficiently large number of solutions. The case generation and the evaluation process are performed hierarchically, dividing the parameters into groups to better solve the solution space, which cannot be achieved with conventional techniques such as traditional point-based design. This methodology is applied as a case study to design three FLNG platforms with different production levels (2, 3, and 4millionmetric tons per year). Performance parameters are defined and evaluated, optimizing downtime, structural mass, and load capacity. The resulting platforms are compared to existing FLNG dimensions. Essential conclusions are drawn about design improvements, such as key dimensions, quantity, and configuration of tanks, freeboard specifications, and operating draft. The developed synthesis framework proved to be a quick and useful tool for the early stages of the FLNG project.\u0000 \u0000 \u0000 The growing global social and demographic development has led the world to face a growing demand for energy in recent decades. Although fossil fuels are still the most widely used primary energy source, emissions of greenhouse gases and other pollutants have been a cause of concern related to the climate and the environment.\u0000","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47024823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As a new technique for the deformation of aluminum alloy plate with complex curved surface which is used in shipbuilding, electromagnetic force assisted line-heating process, or EFALH for short, can promote forming efficiency and produce anticipated curved surface within the range of temperatures required in production. For a start, the process unit and experimental scheme for EFALH were introduced in the article. After the experiment, it was confirmed that the electromagnetic force do have auxiliary effect on the deformation of aluminum alloy plate. Then, for the EFALH process, three-dimensional numerical simulation was performed, and the simulated results were verified by experimental data. Influence on the deformation process caused by the difference in the time and current amplitude of electromagnetic force was studied through numerical simulation. At last, the deformation behavior of the plate under EFALH process has been analyzed from two perspectives, namely the periodism of pulsed electromagnetic force and the loading and unloading procedure in the load cycle caused by electromagnetic force. Nowadays, aluminum alloy plate has been applied more and more extensively in shipbuilding, due to its advantages such as lower density, higher strength, higher stiffness, better corrosion resistance, and excellent welding performance than the traditional steel plates (Wang 1994; Biao 2005; He 2005). It is of great significance to find out an appropriate forming method for the production of double-curved aluminum alloy plates installed at hull stem and stern. At present, there are mainly two forming methods, namely cold forming technology and thermoforming technology.
{"title":"Deformation Behavior of Aluminum Alloy Plate Under Electromagnetic Force Assisted Line-Heating Process","authors":"Rui Li, W. Ji, Yujun Liu, Jiangtao Wu, Xiao Liu","doi":"10.5957/jspd.11210029","DOIUrl":"https://doi.org/10.5957/jspd.11210029","url":null,"abstract":"As a new technique for the deformation of aluminum alloy plate with complex curved surface which is used in shipbuilding, electromagnetic force assisted line-heating process, or EFALH for short, can promote forming efficiency and produce anticipated curved surface within the range of temperatures required in production. For a start, the process unit and experimental scheme for EFALH were introduced in the article. After the experiment, it was confirmed that the electromagnetic force do have auxiliary effect on the deformation of aluminum alloy plate. Then, for the EFALH process, three-dimensional numerical simulation was performed, and the simulated results were verified by experimental data. Influence on the deformation process caused by the difference in the time and current amplitude of electromagnetic force was studied through numerical simulation. At last, the deformation behavior of the plate under EFALH process has been analyzed from two perspectives, namely the periodism of pulsed electromagnetic force and the loading and unloading procedure in the load cycle caused by electromagnetic force.\u0000 \u0000 \u0000 Nowadays, aluminum alloy plate has been applied more and more extensively in shipbuilding, due to its advantages such as lower density, higher strength, higher stiffness, better corrosion resistance, and excellent welding performance than the traditional steel plates (Wang 1994; Biao 2005; He 2005). It is of great significance to find out an appropriate forming method for the production of double-curved aluminum alloy plates installed at hull stem and stern. At present, there are mainly two forming methods, namely cold forming technology and thermoforming technology.\u0000","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41471090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jinho Song, Junhee Lee, Daewoon Kim, W. Kim, Taeseon Kang, Jeung-Youb Kim, Jong-Ho Nam, K. Ko
This article introduces an artificial neural network (ANN) model to determine cycle-times for forming curved hull plates when the target shape is known. The proposed model aids shipbuilding companies in predicting the cycle-times required for ship fabrication. The input parameters are geometric information extracted from the target shape (curvedness, Gaussian curvature, width, and height of the hull plate), and the output parameter is the heating duration per unit area. The structure of the proposed model, which predicts cycle-times for line heating after the cold forming case, consists of two hidden layers. The proposed model is convenient to use and flexible because it only requires retraining when the dataset is changed. The performance of the proposed model was analyzed by five-fold cross-validation and compared with that of a mathematical model obtained from the linear regression analysis method and predefined formulas. The results show that the ANN model is reliable and accurate for the cycle-time prediction of curved hull plates in shipbuilding applications. Shipbuilding companies generally estimate the production cost of a ship based on their previous ships for various purposes before the production planning department begins to optimize the fabrication process. They use the estimated value to refine the overall fabrication process or improve it by reducing unnecessary tasks and maximize the overall production efficiency.
{"title":"Cycle-Time Estimation for Forming Curved Plates Using Neural Networks","authors":"Jinho Song, Junhee Lee, Daewoon Kim, W. Kim, Taeseon Kang, Jeung-Youb Kim, Jong-Ho Nam, K. Ko","doi":"10.5957/jspd.04210012","DOIUrl":"https://doi.org/10.5957/jspd.04210012","url":null,"abstract":"This article introduces an artificial neural network (ANN) model to determine cycle-times for forming curved hull plates when the target shape is known. The proposed model aids shipbuilding companies in predicting the cycle-times required for ship fabrication. The input parameters are geometric information extracted from the target shape (curvedness, Gaussian curvature, width, and height of the hull plate), and the output parameter is the heating duration per unit area. The structure of the proposed model, which predicts cycle-times for line heating after the cold forming case, consists of two hidden layers. The proposed model is convenient to use and flexible because it only requires retraining when the dataset is changed. The performance of the proposed model was analyzed by five-fold cross-validation and compared with that of a mathematical model obtained from the linear regression analysis method and predefined formulas. The results show that the ANN model is reliable and accurate for the cycle-time prediction of curved hull plates in shipbuilding applications.\u0000 \u0000 \u0000 Shipbuilding companies generally estimate the production cost of a ship based on their previous ships for various purposes before the production planning department begins to optimize the fabrication process. They use the estimated value to refine the overall fabrication process or improve it by reducing unnecessary tasks and maximize the overall production efficiency.\u0000","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43351444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article studies the feasibility of using low-cost materials, techniques, and tools to manufacture a 1/100-scale model of a VLCC. For this purpose, three main aspects were considered to reduce the production costs: 1) the bypass to the fabrication of a mold, by building directly the final hull with mid-density fiber wood; 2) the use of a 3 degrees of freedom computer numerical control (CNC) milling machine to cut and shape the pieces of the hull, which can be easily rented at affordable prices; 3) the automation as much as possible of the process to avoid contracting highly skilled personnel to do manual tasks, which would increase substantially the fabrication costs. The article is based on the practical case study of the fabrication of the KVLCC2 (KRISO Very Large Crude Carrier 2) scale model, which is used to describe the digital models, the milling process, and the finishing work. At the end, the validation of the model is done by comparing the final physical hull surface with the original digital one. This study is mainly directed to small maritime research centers and/or universities, which are interested in performing maneuvering experiments with homemade ship scale models.
{"title":"Study on the Feasibility of Using Low-Cost Techniques and Tools to Manufacture a Scale Model of a Ship for Maneuvering Experiments","authors":"J. M. Varela, C. Guedes Soares","doi":"10.5957/jspd.10190054","DOIUrl":"https://doi.org/10.5957/jspd.10190054","url":null,"abstract":"This article studies the feasibility of using low-cost materials, techniques, and tools to manufacture a 1/100-scale model of a VLCC. For this purpose, three main aspects were considered to reduce the production costs: 1) the bypass to the fabrication of a mold, by building directly the final hull with mid-density fiber wood; 2) the use of a 3 degrees of freedom computer numerical control (CNC) milling machine to cut and shape the pieces of the hull, which can be easily rented at affordable prices; 3) the automation as much as possible of the process to avoid contracting highly skilled personnel to do manual tasks, which would increase substantially the fabrication costs. The article is based on the practical case study of the fabrication of the KVLCC2 (KRISO Very Large Crude Carrier 2) scale model, which is used to describe the digital models, the milling process, and the finishing work. At the end, the validation of the model is done by comparing the final physical hull surface with the original digital one. This study is mainly directed to small maritime research centers and/or universities, which are interested in performing maneuvering experiments with homemade ship scale models.","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46352894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to reduce the wave-making resistance of ships, this paper proposes an optimization design method for bulbous bow form based on potential flow theory. In this paper, we restrict our interest to parametric deformation of the bow, at the same time constrain the displacement and the length of the ship. Based on Rankine source method, the wave-making resistances of DTMB5512 and ITTC Ship A-2 are calculated. For optimization, Sobol algorithm is selected to create sample space; based on it, we use Nelder–Mead algorithm to obtain the optimal hull form in the space. Additionally, we compare and analyze the hydrodynamic performance of the ship. The results show that the optimization design method reduces the wave-making resistance of DTMB5512 and ITTC Ship A-2, which verifies the feasibility of the method. Energy Efficiency Design Index (EEDI) guides the future development of the shipbuilding industry toward green ships and accelerates the pace of energy conservation and emission reduction. EEDI is closely related to hull form; therefore, the design optimization of ship hull focus on reducing EEDI becomes the central issue of the current research (Hou et al. 2018).
为了减小船舶的造浪阻力，本文提出了一种基于势流理论的球茎型船首优化设计方法。在本文中，我们限制了对船首参数变形的研究，同时限制了船体的位移和长度。基于朗肯源法，计算了DTMB5512和ITTC A-2船的造波阻力。优化时，采用Sobol算法创建样本空间;在此基础上，采用Nelder-Mead算法求解空间中最优船体形状。此外，还对船舶的水动力性能进行了比较和分析。结果表明，该优化设计方法降低了DTMB5512和ITTC船A-2的造波阻力，验证了该方法的可行性。能效设计指数(Energy Efficiency Design Index, EEDI)引导未来船舶行业向绿色船舶方向发展，加快节能减排步伐。EEDI与船体形状密切相关;因此，以降低EEDI为重点的船体设计优化成为当前研究的核心问题(Hou et al. 2018)。
{"title":"Research on Design Optimization of High-Speed Ship Bulbous Bow Based on Nelder-Mead Algorithm","authors":"Liu Jie, Zhang Bao-Ji, Xu Ning","doi":"10.5957/jspd.07190039","DOIUrl":"https://doi.org/10.5957/jspd.07190039","url":null,"abstract":"In order to reduce the wave-making resistance of ships, this paper proposes an optimization design method for bulbous bow form based on potential flow theory. In this paper, we restrict our interest to parametric deformation of the bow, at the same time constrain the displacement and the length of the ship. Based on Rankine source method, the wave-making resistances of DTMB5512 and ITTC Ship A-2 are calculated. For optimization, Sobol algorithm is selected to create sample space; based on it, we use Nelder–Mead algorithm to obtain the optimal hull form in the space. Additionally, we compare and analyze the hydrodynamic performance of the ship. The results show that the optimization design method reduces the wave-making resistance of DTMB5512 and ITTC Ship A-2, which verifies the feasibility of the method.\u0000 \u0000 \u0000 Energy Efficiency Design Index (EEDI) guides the future development of the shipbuilding industry toward green ships and accelerates the pace of energy conservation and emission reduction. EEDI is closely related to hull form; therefore, the design optimization of ship hull focus on reducing EEDI becomes the central issue of the current research (Hou et al. 2018).\u0000","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42290151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
When a ship is damaged at sea, it is important to predict its behavior as well as whether it is to sink or not. If the ship comes to an equilibrium, the equilibrium position and time should be estimated; otherwise, the time to sink should be estimated. Furthermore, flooding analysis should be carried out not only during the design stage of the ship for preventive reasons, but also after an accident for a better investigation of its causes. In addition, flooding analysis methods that can provide predictions in case of an accident are of particular importance, as there is no time for the required calculations in an emergency. For this purpose, a quasi-static flooding analysis method for the damaged ship in the time domain is proposed in this study. There are a number of studies in which the equilibrium position and time were estimated by flooding analysis. However, most of them have not considered the air pressure effect in fully flooded compartments, and the method of determining the fluid volume in these compartments was not accurate. In the present study, the virtual vent and accumulator method are used to calculate the reference pressure in the fully flooded compartments, and the compartment shape is considered by using polyhedral integration. Also, spilled oil and solid cargo items from the damaged ship are taken into account for realistic flooding analysis. Finally, the damage stability criteria were checked not only in the final state, but also during the entire time of the flooding, as the intermediate states can be more hazardous than the final state. To validate the feasibility of the proposed method, it was applied to a naval ship, which is considerably more stringent for damage stability. As a result, we checked the availability of this study.
{"title":"Quasi-Static Flooding Analysis Method of a Damaged Ship Considering Oil Spill and Cargo Load","authors":"Ki-Su Kim, M. Roh, Seung-min Lee","doi":"10.5957/jspd.10180037","DOIUrl":"https://doi.org/10.5957/jspd.10180037","url":null,"abstract":"When a ship is damaged at sea, it is important to predict its behavior as well as whether it is to sink or not. If the ship comes to an equilibrium, the equilibrium position and time should be estimated; otherwise, the time to sink should be estimated. Furthermore, flooding analysis should be carried out not only during the design stage of the ship for preventive reasons, but also after an accident for a better investigation of its causes. In addition, flooding analysis methods that can provide predictions in case of an accident are of particular importance, as there is no time for the required calculations in an emergency. For this purpose, a quasi-static flooding analysis method for the damaged ship in the time domain is proposed in this study. There are a number of studies in which the equilibrium position and time were estimated by flooding analysis. However, most of them have not considered the air pressure effect in fully flooded compartments, and the method of determining the fluid volume in these compartments was not accurate. In the present study, the virtual vent and accumulator method are used to calculate the reference pressure in the fully flooded compartments, and the compartment shape is considered by using polyhedral integration. Also, spilled oil and solid cargo items from the damaged ship are taken into account for realistic flooding analysis. Finally, the damage stability criteria were checked not only in the final state, but also during the entire time of the flooding, as the intermediate states can be more hazardous than the final state. To validate the feasibility of the proposed method, it was applied to a naval ship, which is considerably more stringent for damage stability. As a result, we checked the availability of this study.","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":"1 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2022-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41435970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dong-sheng Zhao, Liangliang Wu, Tianfei Zhang, Lele Kong, Yujun Liu
Hot cracking is a serious problem in welding of Invar alloy. The weld hot cracking susceptibility of Invar was evaluated using pulsed laser welding on fish-bone sheet experiment. The pulse wave consisted of preheating pulse and welding pulse. Hot cracks that formed along the grain boundary propagated from the weld upper surface to the inside. The experiments show that adding a preheating pulse can effectively reduce the hot cracking susceptibility of Invar alloy. Finite Element Modeling (FEM) calculations and experimental measurement results show that the welding temperature gradient and cooling rate decrease with increasing preheating pulse duration. However, as the preheating pulse duration increases, the hot cracking susceptibility of the Invar alloy does not decrease all the time, but decreases first and then increases. This is because the increase of heat input leads to the increase of shrinkage plastic strain when the preheating pulse duration increases. The maximum tensile strength of the butt welded joint of the Invar alloy was 467.3 MPa, which is 92.3% of the base metal when the preheating pulse duration is 3 ms.
{"title":"Effect of Preheating on Hot Cracking Susceptibility in Pulsed Laser Welding of Invar Alloy","authors":"Dong-sheng Zhao, Liangliang Wu, Tianfei Zhang, Lele Kong, Yujun Liu","doi":"10.5957/jspd.01200002","DOIUrl":"https://doi.org/10.5957/jspd.01200002","url":null,"abstract":"Hot cracking is a serious problem in welding of Invar alloy. The weld hot cracking susceptibility of Invar was evaluated using pulsed laser welding on fish-bone sheet experiment. The pulse wave consisted of preheating pulse and welding pulse. Hot cracks that formed along the grain boundary propagated from the weld upper surface to the inside. The experiments show that adding a preheating pulse can effectively reduce the hot cracking susceptibility of Invar alloy. Finite Element Modeling (FEM) calculations and experimental measurement results show that the welding temperature gradient and cooling rate decrease with increasing preheating pulse duration. However, as the preheating pulse duration increases, the hot cracking susceptibility of the Invar alloy does not decrease all the time, but decreases first and then increases. This is because the increase of heat input leads to the increase of shrinkage plastic strain when the preheating pulse duration increases. The maximum tensile strength of the butt welded joint of the Invar alloy was 467.3 MPa, which is 92.3% of the base metal when the preheating pulse duration is 3 ms.","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43361271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ship maintenance and repair work cost estimation is often regarded as an “Art,” which may contribute to the financial success or distress of a shipyard. Regarded as experts by senior management, estimators are among the most valued resources, and nonetheless, human. Over time, estimators learn from mistakes, and get better with tenure at sharpening assessments. When estimators retire without having groomed an apprentice, shipyards may be at risk of losing a lot of know-how, all at once. These shipyards may well find very costly to experience, for a while, estimating skills stepping back on the learning curve. Yet, even shipyards relying on less advanced information technology may have unwittingly accumulated a lot of valuable data relevant to ship maintenance and repair works. These shipyards may overlook how easily accessible knowledge can be turned into a competitive advantage through predictive analytics. Not only can this data be literally mined, but machine learning algorithms, such as Artificial Neural Networks (ANN), can now process it for a speedy and preliminary estimate through faster and cheaper computing power. To be clear, the purpose is not to replace the human estimator but to help the expert quickly assess, when times are busy, whether to bid or not on a specific project opportunity. In the absence of The Master Estimator, an Apprentice may also look for a quick and cheap sanity check of the prepared estimate before submitting a bid. The study carried out in this article is based on all ship maintenance and repair data recorded at a single North American shipyard over the last 19 years since the current information systems were implemented. This raw data extract with all directly paid hours logged daily by workers on 1277 ship maintenance and repair projects was screened through advanced data cleansing. To enrich the cleansed data tables, additional independent variables were subsequently collected internally and externally to develop a training–testing data set. The final 657 projects represent 136 vessels regrouped in eight types, for which 28 other independent variables were all made available for training up to testing simple ANN models. The scope of this article is limited to the estimation of the direct labor required to complete ship maintenance and repair projects on a specific type of vessels for which workforce planning and tactical pricing was deemed the most relevant to keep the business afloat.
{"title":"Predicting Ship Maintenance and Repair Labor with Artificial Neural Networks","authors":"P. M. Fruytier, Arun Kr Arun Kr Dev","doi":"10.5957/jspd.10200027","DOIUrl":"https://doi.org/10.5957/jspd.10200027","url":null,"abstract":"Ship maintenance and repair work cost estimation is often regarded as an “Art,” which may contribute to the financial success or distress of a shipyard. Regarded as experts by senior management, estimators are among the most valued resources, and nonetheless, human. Over time, estimators learn from mistakes, and get better with tenure at sharpening assessments. When estimators retire without having groomed an apprentice, shipyards may be at risk of losing a lot of know-how, all at once. These shipyards may well find very costly to experience, for a while, estimating skills stepping back on the learning curve. Yet, even shipyards relying on less advanced information technology may have unwittingly accumulated a lot of valuable data relevant to ship maintenance and repair works. These shipyards may overlook how easily accessible knowledge can be turned into a competitive advantage through predictive analytics. Not only can this data be literally mined, but machine learning algorithms, such as Artificial Neural Networks (ANN), can now process it for a speedy and preliminary estimate through faster and cheaper computing power. To be clear, the purpose is not to replace the human estimator but to help the expert quickly assess, when times are busy, whether to bid or not on a specific project opportunity. In the absence of The Master Estimator, an Apprentice may also look for a quick and cheap sanity check of the prepared estimate before submitting a bid. The study carried out in this article is based on all ship maintenance and repair data recorded at a single North American shipyard over the last 19 years since the current information systems were implemented. This raw data extract with all directly paid hours logged daily by workers on 1277 ship maintenance and repair projects was screened through advanced data cleansing. To enrich the cleansed data tables, additional independent variables were subsequently collected internally and externally to develop a training–testing data set. The final 657 projects represent 136 vessels regrouped in eight types, for which 28 other independent variables were all made available for training up to testing simple ANN models. The scope of this article is limited to the estimation of the direct labor required to complete ship maintenance and repair projects on a specific type of vessels for which workforce planning and tactical pricing was deemed the most relevant to keep the business afloat.","PeriodicalId":48791,"journal":{"name":"Journal of Ship Production and Design","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44662184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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