bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation-Based Performance Improvement for Shipbuilding Processes
Authors: Lamb Thomas , Chung Hyun , Spicknall Mark , Shin Jong Gye , Woo Jong Hun , Koenig Philip
Published: January 2021

Shipowners, shipbuilders, the US Navy, and others have a need to evaluate (1) current shipbuilding performance, and (2) projected future performance under a variety of possible technical and managerial scenarios, for the purpose of supporting acquisition and policy decisions, shipyard planning, improvement in shipbuilding processes, new technology insertion and/or development, and capital investment. This need is not restricted to the US shipbuilding environment; it is an important concern even in large, commercially competitive overseas shipyards. In recent years, in various attempts to address the problem, different types of simulation modeling approaches have been investigated by a number of research teams. However, due to the nature of the shipbuilding process, the goal of performing realistic, credible analyses remains elusive. This paper reports on the results of an ongoing international project being conducted by the University of Michigan and Seoul National University. In this project, there are two key emphases:researching and developing improved modeling and/or decision analysis approaches, andrigorous validation of theoretical approaches and models through the use of actual, internationally competitive shipyard production data. Key accomplishments toward these objectives have been made and are reviewed and discussed in this paper.
Study of Rest Time of Workers Using Biomechanical Analysis
Authors: Okumoto Yasuhisa
Published: January 2021

This report focuses on welding work for the assembly of large steel structures as an example of physical jobs. Task simulations using a digital human model, including metabolic energy expenditure analysis, have been carried out using the biomechanical approach for typical welding postures. Moreover, necessary rest time to recover from fatigue has been studied, and the optimal work cycle in a day was examined. As a result, it can be concluded that the flat position for welding, the most widely applied posture, requires the greatest energy expenditure, whereas the overhead position is requires the least. Furthermore, it is concluded that the rule of taking short breaks and often is preferable from the viewpoint of recovery from fatigue, especially for work where the consumption of energy is large. Finally, an optimal work cycle is proposed.
New Horizons for Shipbuilding Process Improvement
Authors: Inozu Bahadir , Niccolai M. J. "Nick" , Whitcomb Clifford A. , MacClaren Brian , Radovic Ivan , Bourg David
Published: January 2021

"In 2004, we start an Initiative—Lean Six Sigma Initiative to achieve our Op Ex Goals. We will be conducting a number of on boarding sessions for Six Sigma with senior leaders in DOD, NAVY, and most importantly Defense Contractors. We will require Six Sigma training for direct reports."John Young, Assistant Secretary of the Navy (Research, Development, and Acquisition)The announcement of NAVSEA's Lean Six Sigma initiative has ushered in a new era in the ways that naval combatants are designed, built, and operated. As the Navy's budgetary constraints increase in the coming years, the challenges they face in the 21st century will grow. New levels of process performance are mandated. This paper first highlights the opportunities that the Lean Six Sigma roadmap brings to shipbuilding process improvement and then details the efforts to adopt Lean Six Sigma and align it with the continuous improvement initiative at Northrop Grumman Ship Systems. Aspects of management strategy, design for Six Sigma, and replicating process improvements as part of integrating Lean Six Sigma with Knowledge Management are discussed.
A Review of the Use of Compensated Gross Tonnes for Shipbuilding Performance Measurement
Authors: Bruce George J.
Published: January 2021

The need for a universal measure of shipbuilding performance has been recognized for many years. To meet the need, the concept of compensated gross tonnes (CGT) was developed within the Organization for Economic and Co-operative Development (OECD), initially as a means of overall comparisons between regions and perhaps nations. Over time, the use has been extended to compare individual companies and also, with a cost element, to compare ship construction costs. More recent work has looked at extending the CGT concept to warship construction. The extended use of CGT as a measure is accepted as less than perfect, but no generally agreed upon alternative has been proposed. This paper reviews the uses of CGT, highlights some of the uses in measurement of shipyard performance, and proposes alternative means of presenting the CGT information that are intended to improve its usefulness.
Virtual Reality Welder Training
Authors: Porter Nancy C. , Cote J. Allan , Gifford Timothy D. , Lam Wim
Published: January 2021

Based on the orientation and travel speed of a welding torch, virtual reality technology simulates gas metal arc welding in near-real time using a neural network.
Shipbuilding Erection Network Optimization: A TSP Method
Authors: Varghese Ranjan , Yoon Duck Young
Published: January 2021

In any shipyard the pre-erection area (PEA) and building dock area are prone to bottleneck formation during the shipbuilding process. This research has made an advancement toward easing this complication by adopting a popularly known genetic algorithm-based approach to the Traveling Salesman Problem (GA-TSP). The foundation and initial condition is projected by an erection sequence network diagram (ESND), which is readily available from the building schedulers in any shipyard. Here, a technology model has been developed that works in three stages: in stage 1, a data collection model is developed to gather the erection block data (geometrical parameters, such as length, breadth, and other attributes) and pitch data (the process delay time between the erection of the blocks); in stage 2, a path optimization model is developed with the erection day as a constraint; and in stage 3, a TSP-based model for the earliest (ENT) and the latest network time (LNT) has been developed. This model has been created to minimize the pre-erected block occupancy load at the PEA by balancing it over the entire working period and eventually fixing the block erection day by meeting optimal conditions of off-critical path blocks without compromising its erection priority. In this research the GA-TSP approach is applied to the given ESND to fix the dates of erection for individual blocks lying outside the critical path, as the uncertainty lies with the erection dates of the off-critical blocks. This solution is found by cross checking the percentage area occupancy in the PEA and by limiting the search span between ENT and LNT as it serves as the lower and the upper bound, respectively. This is compiled as a software product using VC++ compiler with the mentioned stages. Sample outputs show that the proposed methods are very effective in the tests performed. The software helps in easing the day-to-day complications of the schedulers while dealing with the yard data.
Environment-Based Strategic Management Model for Indonesia’s Medium-Sized Shipyards
Authors: Ma'ruf Buana , Okumoto Yasuhisa , Widjaja Sjarief
Published: January 2021

Since the nature of the shipyard differs from general industry, a shipyard strategy formulation model has been developed based on its own business characteristics. This paper presents a proposed environment-based strategy formulation model for medium-sized shipyards. A questionnaire survey of the industry's stakeholders was carried out to identify the internal and external strategic factors of the shipyard's businesses. By using multivariate factor analysis, the strategic factors were identified in both new building and ship repair. The results were then used to develop business environment submodels and a shipyard business matrix. These industry based models were integrated into a shipyard strategy formulation model called YARDSTRAT. Its application and evaluation in two shipyards show that the proposed model could produce more comprehensive strategic options to sustainable competitive advantage for the companies.
Reuse of Ship Product Model Data for Life-Cycle Support
Authors: Briggs Ted L. , Rando Thomas C. , Daggett Thomas A.
Published: January 2021

With the advent of full service contracts by the Navy, shipyards have become responsible for the life-cycle support of ships, including maintenance and logistics data over the life of the ship. Hence, it will become increasingly important for shipyards to efficiently integrate acquisition data with life-cycle support products. In particular, the use of an Integrated Data Environment (IDE), mandated for all ACAT1 acquisition programs, serves to collect and configure design, engineering, and production information during acquisition. This information is also required to develop the logistics data for the ship, including technical publications, as well as support life-cycle support systems. The shipyard's cost and performance of these new Navy contracts will depend on the efficient incorporation of this engineering and design information. The Navy and the aerospace domains are moving toward the adoption of a new life-cycle support standard for technical publication: the International Specification for Technical Publications Utilizing a Common Source Database (also known as S1000D). This standard applies to both land- and sea-specific applications, as well as defense and commercial uses. The purpose of the specification was to address the dramatically rising costs of managing life-cycle support information. The specification adopts ISO, CALS, and W3C standards. In fact, it uses Standard for the Exchange of Product Model Data (STEP) AP239, Product Life Cycle Support (PLCS), as one of its normative standards. The Integrated Shipbuilding Environment (ISE) project has published a technical architecture, including XML-based information models, for the sharing of product model data to exchange design, engineering, and production data. The direct use of such data in the population of technical publications could result in significant savings. This paper discusses the requirements and use cases necessary to define the architecture and process to populate portions of the common source database for ship life-cycle support using product model data in ISE format. Specifically, it addresses the issues involved in generating PLCS technical data directly from ISE product model data and populating a database in accordance with the S1000D standard. Both the S1000D standard for interactive technical documentation and AP239 life-cycle support data will be analyzed based on the ISE technical architecture. The integration of the document-centric S1000D standard with the data-centric AP239 and ISE standards is discussed.
Practical Welding Techniques to Minimize Distortion in Lightweight Ship Structures
Authors: Conrardy C. , Huang T.D. , Harwig D. , Dong P. , Kvidahl L. , Evans N. , Treaster A.
Published: January 2021

The trend in both military and commercial shipbuilding is the increased use of thin steel to reduce weight and improve performance. Complex panel structures have thickness transitions for weight and structural optimization with multiple inserts ranging from 5 to 45 mm. Welding practices developed for thicker plate can result in significant out-of-plane distortion when applied to thin-plate structures. Buckling distortion of complex lightweight panels has resulted in a significant negative effect on manufacturing cost and production throughput, limiting the shipbuilders' ability to produce innovative ship designs. High fitting and welding costs are the consequence of this large welding distortion. This problem is exacerbated as the fairness requirements are tightened. New methods are needed to control distortion when welding thinner materials. To tackle the distortion problems, in 2002 Northrop Grumman Ship Systems initiated a multiyear program to develop distortion-control technology for complex panels. This paper reports the results of a study to develop "best practices" for welding of lightweight structures. Control of welding distortion for thin structures requires control of each welding operation from butt welding of plates through to unit assembly. A general philosophy was applied to minimize welding heat input while maximizing restraint during unit construction. To achieve this, the following techniques were evaluated: increasing restraint during each welding operation, improving fitting practice, weld sequencing, and minimizing welding heat input. Additionally, an active distortion mitigation approach, known as transient thermal tensioning, was investigated for reduction of buckling distortion during thin-panel longitudinal stiffener welding. A series of tests were performed to evaluate various distortion control approaches and to optimize production processes. The culmination of the project will involve demonstrating best practices in the production of thin-steel structures. A plan is also being developed for implementing the most advantageous approaches into production.
Ship Design Workflow Management by Share Fast
Authors: Hiekata Kazuo , Yamato Hiroyuki , Oishi Wataru , Nakazawa Takashi
Published: January 2021

From the viewpoint of technology transfer and education of ship design, it is essential to incorporate design process with knowledge. ShareFast is a methodology for associating knowledge with process and representing them as multimedia information based on semantic web technology. In this methodology, workflows of ship design process are implemented by a software system. It is concluded that the system worked very well to articulate the workflow and design knowledge, and the design process was executed efficiently even by inexperienced engineers.
A Digital Mock-up System for Construction of Product Information Model in Shipbuilding Process
Authors: Kim Won Don , Nam Jong-Ho , Park Ju Yong
Published: January 2021

As a significantly complicated manufacturing process, shipbuilding requires a sophisticated product information model to achieve the seamless flow of product information. A digital mock-up system (DMU) that builds a prototype in a computer has been proposed for consistent quality control. The DMU system can simulate models and assemblies on-the-fly as well as project real-world manufacturability without the expense and time required to make a physical mock-up. However, establishing a DMU system that can facilitate the use of product information is not easy. Preparing useful product information is costly and requires skilled computer engineers. It is thus often infeasible, especially in small and medium-sized shipyards. This paper describes the development of an affordable DMU system. Newly emerged technologies such as eXtensible Markup Language (XML), Unified Modeling Language (UML), and virtual reality (VR) are utilized to set up a practical DMU system. The DMU system developed has been applied to various commercial ships to verify its functionality and practicability.
High-Speed Tandem Submerged Arc Welding of Thin Steel Panels
Authors: Porter Nancy C. , Russell James J. , Conrardy Christopher , Kvidahl Lee G. , Evans Nicholas J. , Sadler Harold A. , Barton David J. , Baughman Brian G.
Published: January 2021

For thin steel, high-speed tandem, narrow groove submerged arc welding procedures were developed with improved flux copper backing using advanced waveform power supplies and controlled weld joint root openings. Preferred parameters produced welds that met Navy mechanical property requirements, improved weld bead quality, and doubled/tripled welding productivity.
A System for Management and Application of Standards in Ship Structural Design
Authors: Zimmermann Michael , Bronsart Robert
Published: January 2021

The design process in the maritime industry is characterized by a close cooperation of many diverse partners working in parallel. In this phase, standardization is used to reduce costs, to improve quality, and to shorten time to market. In this paper, an electronic system for the definition, management, and application of standardized solutions for steel structural design is presented. Information about the approach to data modeling applied and the interaction with existing applications is given.
Application of Combinatorial Optimization and Fuzzy Scheduling to Pipe Assembly Process
Authors: Okumoto Yasuhisa
Published: January 2021

The combinatorial optimization of the sequence for pipe assembly was studied to mass produce the pipe units efficiently using the branch-and-bound method in the previous report by the authors. As a result of the simulation, shortening of the total working hours and a reduction in the middle stock were achieved. However, two problems remained: It was difficult to get an optimization solution in the case of many combinations due to computer time, and only the average time of each working process was taken. For the former problem, the tabu search algorithm has been introduced in addition to the branch-and-bound method, and the revised process of the production has been proposed as a simulation result using this algorithm. For the latter problem, the technique of fuzzy scheduling has been adopted to take into account the variation in working time for each process and in the resulting delivery period. These have been formalized using the fuzziness, and the reliability of the completion time has been calculated for the original process and the improved process. As a result, the proposed process that was calculated by the optimization program has been evaluated as having high reliability, comparing to the original process. According to these studies, it was confirmed that these optimization techniques and the evaluation method of reliability using the fuzzy scheduling technique were quite effective.
Numerical Prediction of Buckling in Ship Panel Structures
Authors: Jung Gonghyun , Huang T. D. , Dongg Pingsha , Dull Randall M. , Conrardy Christopher C. , Porter Nancy C.
Published: January 2021

A shell-element-based numerical module was used to effectively predict welding-induced distortions. The numerical results were validated by comparison with a series of physical test panels. Eigenvalue analyses were performed to evaluate the buckling propensity of each test panel with and without transient thermal tensioning.
A Heuristic Method to Schedule Pipe-Processing Flowshop in a Shipyard
Authors: Jingsong Bao , Xiaofeng Hu , Ye Jin
Published: January 2021

This paper proposes a scheduling system for pipe processing in shipyards to improve productivity. The pipe processing consists of five stages, including cutting, bending, welding preprocessing, argon welding, and CO2 welding. First, the bottleneck stage is selected, and then the longest time processing first (LPT) algorithm is applied to construct the schedules of the bottleneck and the upstream stages. For the downstream stages, the local bottleneck among these stages is selected, and the above scheduling procedure is performed again to construct schedules for the stages ahead of the local bottleneck stage. The scheduling algorithm is applied again and again, until the schedules for all stages have been constructed. Finally, the test is performed on the real data, and the experimental results demonstrate that the proposed algorithm can efficiently improve the productivity of the pipe-processing flowshop.
Fatigue Prediction by Thermographic Method of Aluminum Alloy 6082 Panels: Comparison Between FSW and MIG Welding
Authors: Crupi Vincenzo. , Marinò Alberto. , Biot Marco , Risitanoison Giacomo.
Published: January 2021

This paper focuses on the fatigue behavior of aluminum alloy welded joints, which can represent points of weakness in the ship structure. The traditional methods of fatigue assessment of welded joints have some limitations and are extremely time consuming. The Risitano method, based on thermographic analysis, has been applied to overcome these difficulties by predicting the fatigue behavior of welds. Experimental tests have been carried out to assess and compare the fatigue capability(S-N curves, endurance limits) of different welded joints, obtained by means of friction stir welding (FSW) and metal inert gas (MIG) welding. Fatigue predictions obtained resorting to the thermographic method (TM) show good agreement with those derived from the traditional procedure. Thus, TM proves to be a powerful tool also for the characterization of the kind of welded joints mentioned.
A Linear Programming Approach to Optimization of Ship Design and Construction Phases
Authors: Moyst Howard , Das Biman
Published: January 2021

Labor cost savings can be obtained by considering the effect of design rework on the degree of overlap of the ship design and construction phases. Based on data from a shipbuilding case study, a linear programming (LP) model was developed to investigate the optimum overlap of the design and construction phases. Two scenarios were modeled. The case study's start-up period, which involved design and the construction of four ships, and a hypothetical small batch program to determine the degree of overlap and total hours required for a new shipbuilding program. In each scenario, the LP model found the optimum overlap period for design and construction and the associated total hours. In the first scenario, the analysis demonstrates that by reducing the amount of overlap between the design and construction phases, a reduction in construction direct labor hours can be achieved while obtaining the overall duration and scheduled completion times. In the second case, the analysis recommends a zero overlap policy between the design and construction phases to minimize total hours while achieving the overall schedule duration. When compared with the actual case study results, the zero overlap policy estimates an $8 million saving. The analysis supports the policy to complete design activities with construction-dependency relationships before starting construction.
Activity-Based Spatial Scheduling
Authors: Finke Daniel A. , Ligetti Christopher B. , Traband Mark T. , Roy Allan
Published: January 2021

In this paper we describe the development and implementation of a tool that allows shipyard planners and construction managers to efficiently and effectively plan work area space within large manufacturing facilities. Currently, there are no software planning tools available to explicitly plan and schedule critical manufacturing space. The activity-based spatial scheduling tool described in this paper can be used by planners and construction management teams to easily reserve space within shipyard facilities for the construction and outfitting of large units. The Activity-Based Spatial Scheduling Tool gives users the ability to rapidly generate and compare multiple space allocation plans, with the ultimate goal of maintaining the critical ship construction schedule.
Application of Heating Line Computation Model in a Shipyard: A Case Study
Authors: Park JungSeo , Shin JongGye , Kim YoungBum , Kim HoKyeong , Cho SungAm , Leem HyoKwan , Ko KwangHee
Published: January 2021

A ship hull is largely made of curved plates, and some of them are doubly curved ones that are not developable. They are formed by the line heating method that has been used for a long time in ship construction. There have been a lot of efforts to automate the line heating process, and a practical algorithm for line heating information was developed. The algorithm, based on differential geometry and kinematics analysis of plates, was efficient in terms of computational time. Up to now, however, its applicability to the real shipyard process has not been evaluated. In this paper, we develop a software framework for heating line computation, test it with real ship hull pieces, and verify that the information from the algorithm matches worker's know-how in practice.
Research and Development of CNC Cool Frame Bender
Authors: Li Pei-yong , Wang Chengfang , Mao Yunsheng , Hu Yong , Zhou Yongqing
Published: January 2021

A new type of ship's frame bender with computer numerical control (CNC) has been developed and installed in many shipyards. The bender has many advantages and will result in significant cost savings and increased production efficiency. The CNC bender is compatible with existing shipyard automation programs, using the frame data generated by a computer-aided design/computer-aided manufacturing (CAD/ CAM) system to produce a formed frame automatically. The bender can straighten deformed beams in both horizontal and vertical planes, as well as bend them in the horizontal plane without out-of-plane deformation. Markings can be stamped at the required position in the bending process.
The National Shipbuilding Research Program Contribution in Advancing Information Technology in the Shipbuilding Enterprise
Authors: Wood R. , Gischner B. , Karns L. , Fowler J.
Published: January 2021

The purpose of the National Shipbuilding Research Program is to apply information technologies that can reduce the cost of building and maintaining US Navy warships. The program targets solutions to consensus priority issues that exhibit a compelling business case to improve the efficiency of the US Shipbuilding and Ship Repair Industry and involves US shipyards, academia, technology companies, and government agencies. The projects are funded by the government with equal cost shared by project participants. The Systems Technology area projects involve all portions of the industry and cover a wide array of projects including: Product Information Modeling, Business Process Technologies, Common Parts Catalog (CPC), Automatic Generation of Control Program for Robotic Welding, Shipyard Design Tool Enhancement, Capturing As-Built Models For 3D CAD Systems, Shipyard Equipment Wireless Monitoring And Control, Open Architecture Standards, and Other Shipyard Computer Applications.
Hybrid Laser-GMA Welding for Improved Affordability
Authors: Reutzel E. W. , Kelly S. M. , Sullivan M. J. , Huang T. D. , Kvidahl L.
Published: January 2021

Maturing high-power solid-state laser technology is fueling an interest in hybrid laser gas metal arc (laser-GMA) welding for shipyard fabrication activities. Hybrid laser-GMA welding has demonstrated an ability to both reduce the distortion of thin steel butt welds and increase the production rate of pipe welds relative to conventional joining techniques, both leading to improved affordability. The paper discusses the potential benefits of hybrid laser-GMA welding, results of experiments to address both distortion and production rate, and provides an overview of a hybrid pipe welding system recently installed in a shipyard.
Optimization of Welding Route by Automatic Machine Using Reinforcement Learning Method
Authors: Okumoto Yasuhisa
Published: January 2021

A ship hull block is generally composed of skin plates, longitudinals, and transverse webs as a grillage structure, and longitudinals and transverse webs are joined by a fillet weld on a skin plate panel. Then much labor time is necessary for this welding work because many welding lines exist. Now, a simple automatic welding machine using a truck system is applied widely as well as semiautomatic CO2 weld or gravity weld. Since the automatic welding machine needs the help of workers for initial setting, turning, and shifting, the efficient routing has to be investigated for the improvement of productivity. However, it is difficult to find an optimal weld sequence when weld lines increase and then the combination number of welding sequence increases. Such research is called combinatorial problem. This paper examines how to decrease the work time using the reinforcement learning method, which imitated the behavior pattern of animals.
Differences in Fatigue Strength Between Arc and Laser Hybrid Welded Joints
Authors: Remes H. , Varsta P.
Published: January 2021

This paper presents the results of fatigue tests, including tests of laser hybrid and arc welded butt joints, for two plate thicknesses, 6 and 12 mm. Pure laser welded joints were also tested. The S-N curves based on nominal stresses for the different welded joints are presented. The results were further analyzed using the notch stress approach, where the fatigue notch factors were determined from the measured geometries of the welded joints. Unexpected differences in the S-N curves based on the notch stresses were found between the laser hybrid and arc welded joints and between the laser hybrid and pure laser welded joints. The reasons for this difference were studied with the help of extensive measurements of weld notch geometries. Significant differences in the geometries were observed. Taking into account the notch geometry and the notch depth, the notch stress approach partially explains the differences between the fatigue endurance limits of the laser hybrid and arc welded joints. The applicability of the notch stress approach to the fatigue design of laser hybrid welded joints is also discussed.
Effect of Toe Grinding on Fatigue Strength of Ship Structure
Authors: Ryu Hong Ryeul , Kim Wha Soo , Ha Woo Il , Kang Sung Won , Kim Myung Hyun
Published: January 2021

It is well known that grinding the weld toe is not only effective in increasing the fatigue life at the weld joint by removing the initial defect and by reducing the stress concentration, but also rather convenient to apply and survey at the construction stage without special equipment or techniques. In this research work, comparative fatigue tests have been performed for a total of five types of weld specimens: three types of small welded specimens and two types of small-scaled structural models. According to the results of the fatigue tests, the enhancement factor of fatigue life by toe grinding for small welded specimens is determined to be about 6 to 10. However, the enhancement factor of fatigue life by toe grinding for small-scaled structure is 1.9 to 5.4. In the case of small welded specimens, once the crack is initiated to a certain level, then the crack propagation is accelerated rapidly due to simplicity of structural shape. In the case of actual ship structures, however, even after the crack is initiated to a certain level, the crack propagation is not accelerated as much due to structural redundancy. The toe grinding is only beneficial in extending the crack initiation life. Accordingly, the effect of toe grinding on the fatigue life at the actual structure is not as predominant as the one at the small welded specimen.
Strength and Deformability of Corroded Steel Plates Estimated by Replicated Specimens
Authors: Sumi Yoichi
Published: January 2021

Strength and deformability of corroded steel plates are investigated using artificially pitted and replicated specimens processed by a computer-aided design/computeraided manufacturing (CAD-CAM) system that numerically controls a desktop milling machine to produce or replicate the surface geometry of a corroded surface. Periodic array of surface pits are made for self-similar specimens. Also, corroded surfaces are measured by scanning a plate by a laser displacement sensor, so that the surface data are stored to generate the input for the CAM system. As a typical example of plates with general corrosion, surface geometries of a sample specimen taken from the bottom plate of an aged tanker are reproduced, and the corresponding tensile tests are carried out. The reduction of the tensile strength is slight, while that of the elongation is significant. In order to examine the extent of the corroded surface, test specimens having different sample area but with the same thickness are tested, where the surface undulation is machined in the same scale. The test results show a slight dependence on the extent of the surface area.
Simulation of Inspections on Ship Plates With Random Corrosion Patterns
Authors: Teixeira A. P. , Guedes Soares C.
Published: January 2021

This paper investigates how the number of thickness measurements and the location of each measurement influence both the correct representation of the level of corrosion and indirectly the correct assessment of the collapse strength of the corroded plates. For this purpose, the corrosion patterns are represented by random fields, which are then discretized using the Expansion Optimal Linear Estimation method. This approach is used to simulate the present practice on thickness measurement patterns and to identify what would be the effect of other strategies of measurement patterns for representing the corrosion in terms of prediction of the average reduction of plate thickness. Finally, the collapse strength of the plates with nonuniform corrosion is calculated by nonlinear finite element analysis and its correlation with the average reduction of plate thickness obtained from the different measurement patterns is assessed.
A Study on Generation of Compound Curved Surfaces by Line Heating Using Oxyacetylene Gas Flame
Authors: Biswas Pankaj , Mandal N. R. , Sha O. P
Published: January 2021

In shipbuilding, one of the most tedious and human skill dependent operations is plate forming for producing compound curved plates. Line heating can be gainfully applied for fabrication of such plates. The surface properties of these compound curved plates have a significant effect on the line heating process. For generation of the heating line pattern to achieve the target surface, the surface properties are required. The strain distribution of a curved surface needs to be evaluated to determine the extent of line heating. In this present work, a suitable program has been developed to determine the surface properties (i.e., generation of required grid points, Gauss curvature, principal curvatures, and their directions) and the heating line pattern by using B-spline surface theory. For getting the initial template (blank) and strain distribution over the plate, a numerical technique and an optimized strain field distribution approach based on minimization of total strain energy has been used. The theoretically generated surfaces compared fairly well with the experimentally produced compound curved surfaces using the numerically obtained line heating patterns.
A New Check Method of Lifting Padeyes Based on Frictionless Cylindrical Contact Theory
Authors: Bo Zhou , Yujun Liu , Zhuoshang Ji
Published: January 2021

The lifting padeyes are widely used in the construction of offshore structures and ships. Because of the lack of more accurate information, heavily conservative simplified approaches have to be applied to strength analysis and structure design. Therefore, the calculated stress results contain a lot of discrepancies with the actual stress. In the paper, a robust stress check formula is derived using the theory of frictionless cylindrical contact. The influences of padeye thickness and clearance ratio on contact stress are analyzed. It is shown that the new expressions account for a better representation of the real stress value and distribution. By applying the strength check formula presented in the paper, the safe reliability of structure design can be improved significantly.
Experimental Study on Friction Stir Welding of Marine Grade Aluminum Alloy
Authors: Biswas Pankaj , Mandal N. R.
Published: January 2021

Friction stir welding, a comparatively new joining technique, is mainly used for welding aluminum alloys. In the present work, an attempt has been made to study the effect of weld parameters of friction stir welding of marine grade 5083 aluminum alloy. Several test runs were conducted to assess the effects of tool rotating speed and tool traverse speed on the microstructure and mechanical properties of the welded joint. It was observed that the tool traverse speed has a significant effect on the end properties of the welded joint. Grain refinement was observed in the thermomechanically affected zone (TMAZ), which led to improved mechanical properties of the welded joint. However, an increase in welding speed keeping rotational speed constant led to deterioration of mechanical properties. The study strongly indicates a possibility of achieving a superior welded joint in marine grade 5083 aluminum alloy with adequate selection of process parameters.
Research for Springback of CNC Frame Cool Bending
Authors: Li Pei-yong , Xue Jiang-shan , Zhou Yong-qing , Wang Cheng-fang , Mao Yun-sheng , Hu Yong
Published: January 2021

Springback is the key technique for the control of the computer numeric control (CNC) frame bender. Research had been done for the springback of frame cool bend. This paper proposed the regression analysis results with samples of frame bend production recorded in the shipyard. The characteristics of the frame bending with trial-and-error method had been analyzed. Based on the regression function of the sample, this paper proposed a forming control method by excess bending and the amount of control parameter can be calculated with the regression function. In this way, one or two operations were needed to achieve the acceptable shape of the section. This method can increase the efficiency of frame bend production obviously. A new control system had been proposed with this control method, the system had been applied in the frame bender in shipyard, and the production efficiency had been increased effectively.
Evaluation Criterion of Machinery Arrangement Design in a Ship Engine Room
Authors: Kim Soo-Young , Moon Byung-Young , Shin Sung-Chul
Published: January 2021

The aim of this study is to establish an objective evaluation function that can be used to compare alternative layouts by employing the quantification of particularities of arrangements in ship design. The arrangement of the machinery parts in a ship's engine room is decided at the design phase along with the location of various types of equipment that are located in a compartment. The design needs to maximize the function of every component, while taking into consideration the limited space of the ship. The addition and modification of requirements frequently occurs during the development process of a ship. Therefore, the ship designer suggests several alternative layouts, though only one layout is selected for the final design. This process depends on the experience, knowledge, and judgment of an expert designer, and it is consequently difficult to objectively evaluate the ship design. Therefore, according to quantification by using the fuzzy theory, we suggest a standard that can objectively evaluate alternative layouts to determine the most successful design. In order to provide a standard of evaluation, several evaluation functions are considered and established. By observing the results of the proposed method, the effectiveness of the proposed method is discussed. The results proved the convenience of the location of equipment in the space and the minimum size of the arrangement space in the engine room as well as the interrelationship between each type of equipment. Also, the proposed method showed the pipe producibility in ship building. As a result, the proposed method will contribute to reduce the production cost of ships.
Ship Purchasing: Characteristics, Empirical Evidence, and Market Attractiveness for Shipbuilders
Authors: Pinto Marcos M. O. , Colin Emerson C.
Published: January 2021

This paper presents an analysis of the ship purchasing process and suggests to shipbuilders a methodology to identify the attractiveness of different markets in terms of location. Two analyses are carried out to identify if there is any correlation between exporting country and buyer size (e.g., are Korean exports focused on large clients?) and if the location of the production influences the purchasing decision of the ship buyer. We created a purchasing preference index (PPI) that can be computed for each type of ship and each builder-buyer country pair, and the PPI distribution over several countries is used to evaluate the entry potential for each country which, made up from market size, defines a simple market attractiveness measure. Further analysis is performed aiming to investigate company-level characteristics, such as the size of the players and loyalty in the relationship builder-buyer.
Module Division Planning Considering Uncertainties
Authors: Asok Kumar Ajay , Aoyama Kazuhiro
Published: January 2021

During the module division planning process, various factors such as shipyard facilities, ship structure, outfitting, material availability, and so forth must be considered simultaneously. At the early design stage, detailed information on these factors or constraints might not be certain. This uncertainty makes the generation of optimum module division plan difficult. In this paper, a system is proposed for module division planning considering the uncertainties in the information at the early design stages. Module division planning is defined as the process of selection of the best module division seam locations. Module division plans are evaluated and ranked based on the locations of seams in each pattern and also the properties of modules in each the pattern. Various factors affecting module division planning and their uncertainties are also considered. Based on the evaluation, some of the "preferable" module division plans can be selected. The system is developed based on graph theory and fuzzy logic.
Benchmarking Shipbuilders’ Turnover of Main Assets
Authors: Colin Emerson C. , Pinto Marcos M. O.
Published: January 2021

This paper presents an analysis of the historical and current asset turnover of several shipbuilding companies and regions, such being responsible for more than 50% of global production. Several turnover measures are used including, as inputs, main physical assets such as dock area, berth length, and lifting capacity; and as outputs, compensated gross tonnage (CGT), and the number of different ships produced. Data Envelopment Analysis is used to gauge the inputs and outputs of the companies in order to define their efficiency and identify the benchmarks in terms of asset usage. Results consolidated by region indicate that there are efficient companies producing in all of the regions studied: China, Europe, Japan, and Korea.
A Comparative Study of Three Different Approaches of FE Analysis for Prediction of Welding Distortion of Orthogonally Stiffened Plate Panels
Authors: Biswas Pankaj , Mandal N. R.
Published: January 2021

One of the most disturbing aspects in structural assembly is welding distortion. These deformations adversely affect the subsequent fit-up and alignment of the adjacent panels. The extent of distortion depends on welding parameters, plate thickness, thermophysical properties of plate material, structural restraints, and welding sequence. Because welding is a fully transient phenomenon, its numerical analysis is highly time consuming, and hence analysis of full-size ship structural panels is simply not feasible using conventional finite element (FE) analysis. The computational time depends on number of elements, type of analysis, number of load steps, and computer configuration. Actual simulation of welding, that is, transient elastoplastic thermomechanical analysis is computationally highly time consumable. In the present study, two different modeling approaches for welding distortion prediction are presented that show a drastic reduction in computational time. Finally, comparative studies are made among the transient elastoplastic thermomechanical analysis and two different equivalent techniques, that is, inherent strain method and transient cooling phase analysis for prediction of welding distortions of a stiffened plate panel.
Qualifications of Adhesives for Marine Composite-to-Steel Bonded Applications
Authors: Ritter George W. , Speth David R. , Yang Yu Ping
Published: January 2021

This paper describes a straightforward method for the design and certification of adhesively bonded composite to steel joints for the marine industry. Normally, certification is based on documented service at sea. Since these joints have not been previously deployed at sea, no data on their performance exist. Using an integrated combination of mechanical property evaluation and finite element modeling, the load- bearing capacity of a joint can be compared with the anticipated seaway loads. Calculated factors of safety for the sandwich design used here show that the joint has adequate strength to maintain structural integrity even after severe environmental exposure.
Innovative Ship Block Assembly Production Control Using a Flexible Curved Block Job Shop
Authors: Dong Fang , Parvin Hoda , Van Oyen Mark P. , Singer David J.
Published: January 2021

Operational flexibility is a powerful but complex strategy that is increasingly used in manufacturing and service industries. We introduce operational flexibility to ship production as a method to alleviate the effects of delays that ultimately create issues such as high cost, high variability in production workload, ineffective production control, and resultant low facility use. Our emphasis is on how incorporating a flexible curved block job shop can, with appropriate control/scheduling, increase the efficiency and timeliness of the block assembly process for both flat and curved blocks and enhance the robustness of the shipbuilding system. We formulate a stochastic model of our approach, as a flexible controlled queuing network in particular, and we provide a simulation test bed to quantify the value of this flexibility.
Weight and Cost Optimization of Midship Section Using Common Structural Rules
Authors: Sayebani Mesbah , Mohammadrahimi Abdolhossein , Looyeh Hossein Khoshdel
Published: January 2021

Cost and weight optimization in ship construction are usually investigated in the form of a multiobjective optimization problem. So far, many studies have been carried out to achieve various types of existing optimization objectives and different tools have been developed. Most of the studies in the field of structural optimization have focused on comparing the available optimization algorithms. In this study, a rule-based tool is developed based on the Common Structural Rules (CSRs), which despite its simplicity in application, provides high capabilities in producing an optimal solution. In the developed tool, structural analysis of serviceability limit state is performed by using the relationships of CSRs. The computational tool is created by MATLAB software (Mathworks, Natick, Massachusetts), and the optimization technique is a genetic algorithm. The performance of the computational tool is evaluated by analyzing the midship section of a chemical tanker. In the optimization procedure, weight and cost are assumed to have the same importance. From the results of the developed tool, all components of the weight and cost of ship construction decreased in the optimal solution relative to the initial design.
Analysis of Structural Steel Renewal Locations in Ship Repairing
Authors: Dev Arun Kr , Saha Makaraksha
Published: January 2021

Structural steel renewal in ship repairing is a routine work throughout the service/ operational life of a ship. Prior information about the renewal quantity helps the shipowners to allocate an appropriate budget and the shipyard to prepare the proper ship repairing schedule. It, in turn, helps the shipowners make a financial commitment for cargo. Likewise, prior information about the location of steel renewal works can help the shipowners to prepare the ship before going to the shipyard and the latter to plan for the required logistics. By doing so, the shipowners would be able to save cost in terms of less idle time in the shipyard. The latter can also increase the revenue in terms of minimizing mobilization time. Structural steel renewal location-related information for 123 cargo ships of various ages, deadweights, and types were collected from a single shipyard. Data of renewal locations of selected structural members were analyzed and presented in both tabular and graphical forms. The intention was to show the behavior of renewal locations with respect to the ship’s dimension appropriate for respective structural members, age, and length of the ship. In this article, the authors have attempted to identify and establish the possible root causes that influence the renewal locations and also to investigate and suggest the potential interrelationships between renewal locations, age, length, and type.