bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Loading Fields on Marine Objects
Authors: Ziha Kalman
Published: January 2021

This technical note evokes directionally nonuniform loading field effects on exposures of marine objects and structures in service under environmental conditions. The note firstly reveals the statistical variability of distributions of probabilities and the entropy concept of uncertainty of systems of events for identification, ordering and presentation of probabilistic seasonal nonuniformities of wind wave loading fields. This paper provides diagram of variability of wind wave directions and the chart of ocean-wide directional nonuniformities compiled from the Global Wave Statistics (GWS). It also considers seasonal loading field distributions of wind wave heights against wave directions as well as methods for calculation and presentation of directional exposabilities of marine objects and structures. The study introduces two methods for favorable placement and selection of sustainable directions of marine objects and structures exposed seasonally to nonuniform wind wave loading fields based on criteria for minimal average exposure and on robust uniform exposures during service period. The note elaborates examples of favorable placement of a marine object on six piles near the east Brazilian coast and of an oil tanker in the Gulf of Mexico. The note at the end illustrates the use of the multiple-criteria approach either to support decisions about optimal placement and sustainable headings to waves or for avoidance of unfavorable directional field effects and their combination on marine objects and structures.
Trim and Draft Control Capability of the Variable Buoyancy Ship
Authors: Parsons Michael G. , Kotinis Miltiadis
Published: January 2021

The Variable Buoyancy Ship concept has been developed to address the problem of the introduction of nonindigenous aquatic species (NIS) into coastal waters. While this ship design concept essentially eliminates the transport of NIS across the globe, it presents special problems for operators with respect to their control of trim and draft. An investigation was, therefore, undertaken to assess this capability and ensure that adequate capability would be provided. To better visualize this issue, the equilibrium polygon used in early submarine design has been adapted to provide an effective way to characterize the trim and draft control capability of surface vessels. The results of this investigation and resulting design concept modifications are presented.
Virtual Reality Supported Assembly Planning in the Shipbuilding Industry
Authors: Lödding Hermann , Friedewald Axel , Heinig Martin , Schleusener Sebastian
Published: January 2021

The increasing competition in the shipbuilding industry calls for efficient manufacturing processes. The adherence to budget and due dates requires accurate planning and fast reactions to unplanned events such as late deliveries of assembly parts. Virtual reality (VR) is a tool that can help improve these reactions. To be able to benefit from VR, the tool has to support the examined cases. Current VR solutions do not provide enough support for this; in particular, the problem of parts delivered late has not yet been solved efficiently because of the time-consuming and error-prone manual session preparation. There is no concept for an automatic session preparation according to the new assembly situation and no software-based support for finding and verifying a new assembly sequence using virtual reality. Within the research project Power-VR, an assembly planning prototype has been developed to assist the user during the entire review process. The user is provided with an automatic session preparation as well as with methods for investigating several assembly issues. Examples are the review of a specific ship section as well as the verification of a part assembly under consideration of assembly dates of the affiliated parts. Dynamic concatenation of model data with meta data during the session offers the possibility to automatically filter the parts of the model according to different kinds of information such as the delivery dates. The prototype further supports the finding and verification of assembly sequences by providing necessary information, for example, about the next part to assemble. Also an automatic model preparation for collision control is procured. The developed prototype can be handled immersively during the session. To further improve the control of the available functions, the use of a tablet PC is suggested. This device allows for a more flexible interaction with the system than the traditional flystick and provides additional information, adapted menus and buttons.
Trends in Industry Applications of Computational Fluid Dynamics for Maritime Flows
Authors: Peric Milovan , Bertram Volker
Published: January 2021

This paper surveys developments in Computational Fluid Dynamics (CFD) applications for maritime structures (ships, propellers, and offshore structures) over the past decade. Progress is significant in integrating the process chain, particularly more automated model generation. Increased hardware power and progress in various aspects of the flow solvers allow more sophisticated applications and wider scope of applications. Selected examples taken from industry and research applications show the increasing importance of CFD in earlier design stages.
Automatic Generation of Assembly Sequence for the Planning of Outfitting Processes in Shipbuilding
Authors: Wei Yan , Nienhuis Ubald
Published: January 2021

Outfitting processes are distinguished by interferences, disturbances, great interdependencies and different surrounding area requirements. Their complexity is even more intensified by the use of outsourcing and subcontracting, a broader strategy of western shipyards. Currently, execution planning of outfitting processes is not sufficiently considered. Yards play the role of director and only provide the subcontractors with a general time framework for outfitting. Meanwhile, each subcontracted company plans its own progresses towards its own work, independent from other executers. Consequently, outfitting processes are delayed, frequently caused by space collision, rework, and long-time waiting on the work site. This adversely affects the execution. With the research discussed in this paper, an automatic sequence generation system, which is able to generate the interference-free assembly sequences that identify the relationships among outfitting activities and estimate the reasonable mounting time, has been developed. It is expected to provide each party involved in advanced outfitting with a holistic planning. Hence, the onsite coordination and installation effort maybe reduced and the level of advance outfitting practices maybe increased, which leads to the reduction of cost and lead-time.
The Impact of Contracts on Ship Design Preparation
Authors: Fisher Kenneth W.
Published: January 2021

The implementation of vessel designs is usually achieved through contracts for ship construction or conversion. Accordingly, the design process and the design organization's product have to anticipate and take into account the constraints and requirements of the contracts that control the use of the design, as well as the contract that initiates the design process. This paper addresses the most common contractual factors that have to be considered during preparation of ship designs.
Flexibility in Early Stage Design of U.S. Navy Ships: An Analysis of Options
Authors: Page Jonathan
Published: January 2021

This paper is a summary of my thesis work at the Massachusetts Institute of Technology (MIT). It explores design options for naval vessels and provides a framework for analyzing their benefit to the Navy. Future demands on Navy warships, such as new or changing missions and capabilities, are unknowns at the time of the ship's design. Therefore, ships often require costly engineering changes throughout their service life. These are expensive both fiscally – because the Navy pays for engineering and installation work – and operationally – because either a warship cannot carry out a desired mission need or is carrying out a mission for which it was not initially designed. One method of addressing uncertainty in capital assets is imbedding flexibilities in their architecture. The paper offers early stage design suggestions on flexibilities for naval platforms to incorporate preplanned repeats of the platform with new or different missions. A conceptual platform created – the SCAMP – includes each of these suggestions in its architecture. Then, the paper summarizes an analysis framework similar to real options to evaluate the value of including these expansion options in early stage design versus traditional design methods and their products. The analysis uses a version of the MIT Cost Model for early stage ship design to determine acquisition and life cycle costs. The model was modified to support this analysis by allowing a simulation of possible mission changes with their severity distributed stochastically over a realistic time horizon. Subsequently, the model calculates these effects on life cycle cost. The most important result is the value of the framework for evaluating these managerial options. This framework can be extended to the subsystem level or to the system-of-systems level. In this application, the model predicts that, on average, a flexible platform should not only cost less to build, but also reduce modernization costs by 9% per ship over its life cycle. Therefore, counter-intuitively, building a lesscapable ship with the flexibility to expand capabilities or switch missions actually provides greater expected utility during its service life.
The Potential Conversion of the U.S. Great Lakes Steam Bulk Carriers to Liquefied Natural Gas Propulsion – Initial Report
Authors: Parsons Michael G. , O'Hern Patrick J. , Denomy Samuel J.
Published: January 2021

The feasibility and potential benefits of converting 10 remaining U.S. flag Great Lakes steamship bulk carriers to liquefied natural gas (LNG) propulsion using gas engines is investigated. This is the initial report of a study that began in November 2011. The evolving marine air emissions standards and the movement to LNG fuel in international nonLNG carriers are briefly reviewed. The case for the possible conversion of the remaining U.S. flag Great Lakes steamship bulk carriers to LNG fuel is outlined. Initial results of a conceptual design study on the conversion of the three AAA class vessels (SS Arthur M. Anderson, SS Cason J. Callaway, SS Philip R. Clarke), focusing primarily on operational and arrangement feasibility, is then presented.
Addressing Complexity Aspects in Conceptual Ship Design: A Systems Engineering Approach
Authors: Gaspar Henrique M. , Rhodes Donna H. , Ross Adam M. , Ove Erikstad Stein
Published: January 2021

This article approaches the complexity aspects of conceptual ship design from a systems engineering point of view. We introduce the issue by defining the term complexity in systems engineering, placing the conceptual ship design task as a complex system problem and creating analogies between generic complex systems and a ship. Five main aspects of complexity are presented, linking challenges of the conceptual phase to each of the aspects. The structural aspect is related to the arrangement and interrelationship of the physical objects in the ship. The behavioral aspect derives from the form-function mapping. The external circumstances to which the ship is subjected are approached through the contextual aspect. Uncertainties in the scenarios and changes over time are related to the temporal aspect. The perceptual aspect relates to how stakeholders perceive the value that they receive from a chosen design. A theoretical study to address these five aspects is presented, applying the responsive systems comparison method in the conceptual design of an anchor handling a tug supply vessel. The last section discusses why decomposing the complexities of the ship design task in five aspects is a benefit.
Game Theory and the Shapley Value Applied to a Vessel’s Drydocking
Authors: San Cristóbal José
Published: January 2021

Vessels typically have to be drydocked every 3 or 4 years. These drydockings mean an increase in costs and a reduction in revenues as a result of the time the vessels remain drydocked. Faster completion of these drydockings involves advantages for the shipowner, because ships can enter markets early and create additional revenues. In project management there are many situations in which cooperative behavior of all those involved in it may result in the interest of the firms carrying out a project. The method adopted for allocating the benefits or costs of this cooperation among the firms will affect the willingness of these firms to remain active in the coalition. In this article, the Shapley value is applied to fair allocation of gains obtained by cooperation among several firms carrying out a vessel drydocking who form a coalition to expedite it.
Hull Design Method Combining an Innovative Flow Solver Coupled With Efficient Multivariate Analysis and Optimization Strategies
Authors: Geremia Paolo , Maki Kevin J. , Lavini Gianpiero , Genuzio Harpo
Published: January 2021

An important application of optimization of a ship is the minimization of calm-water resistance for a given displacement. In this work, an innovative flow solver that combines free-surface effects with a viscous solution allows for an accurate drag prediction with fast turnaround times ideally suited for an optimization study. A large number of geometrical-design variables are considered in early-stage design; thus, in this article, different techniques are examined to reduce the curse of dimensionality. Different methods such as multivariate analysis are used to optimize the hull with respect to resistance over a range of different speeds for a given displacement.
Uniform-Panel Weld Shrinkage Data Model for Neat Construction Ship Design Engineering
Authors: Yang Yu-Ping , Castner Harvey , Dull Randy , Dydo James R. , Fanguy Dennis
Published: January 2021

A weld shrinkage prediction model was developed for thin uniform ship panels to predict in-plane shrinkage. The weld shrinkage prediction model consists of a series of empirical equations developed by analysis of shrinkage data from welded panels fabricated in the shipyards. These panels ranged in thickness from 3 mm to 9.5 mm and were welded with processes including submerged arc, flux cored arc, and gas metal arc welding. All fabrication data were carefully recorded using practices that were common over each of the shipyards. Measurements of the panels were made throughout each step of fabrication to provide accurate weld shrinkage data. The data were then analyzed by regression analysis to produce equations that permit the calculation of weld shrinkage based on the conditions used for fabrication. These shrinkage model equations were embedded in a Microsoft Excel spreadsheet for ease of use.
Comparisons Between Prediction and Experiment for Lift Force and Heel Moment for a Planing Hull
Authors: Judge Carolyn Q.
Published: January 2021

Even in calm water, high-speed vessels can display unstable behaviors such chine walking, sudden large heel, and porpoising. Large heel results from the loss of transverse stability at high forward speed. When a planing craft begins to plane, the hydrodynamic lift forces raise the hull out of the water. The available righting moment resulting from the hydrostatic buoyancy is, therefore, reduced. As the righting moment resulting from hydrostatic buoyancy is reduced, the righting moment resulting from dynamic effects becomes important. These hydrodynamic righting effects are related to the hydrodynamic lift. This article explores the relationship between the hydrostatic lift and righting moment, the hydrodynamic lift and righting moment, and the total lift and heel-restoring moment of a planing craft operating at planing speeds. A series of tow tests using a prismatic hull with a constant deadrise of 20 measured the lift force and righting moment at various angles of heel and at various model velocities. The model was completely constrained in surge, sway, heave, roll, pitch, and yaw. The underwater volume is determined from the known hull configuration and the underwater photography of the keel and chine wetted lengths. The results presented include the total lift and righting moment with the hydrostatic and hydrodynamic contributions for various model speeds at two model displacements.
Scaling of Resistance From Surface-Effect Ship Model Tests
Authors: McKesson Chris B. , Doctors Lawrence J.
Published: January 2021

In the case of conventional (displacement) hulls, model testing is based on the assumption (with or without certain refinements) that the total resistance can be expressed as:RT=RF+RR(1)where Rt is measured in the towing tank, and the frictional resistance, Rf, can be accurately estimated by the application of a friction line and the use of the calm-water wetted surface. It is assumed that the dimensionless residuary resistance RR is the same for the model and the prototype vessel. Our article may be considered to be an extension of the classic article by Wilson, Wells, and Heber (1978) to the more complex case of the surface-effect ship, as follows. Specifically, we opine that:RT=RF+RW+RH+RS+RM+RSPRAY(2)Here, Rw is the wave resistance of the vessel (caused by a combination of the actions of the cushion pressure and the two sidehulls), RH is the transom (hydrostatic) drag, Rs is the seal drag, Rm is the momentum drag, and RspRay is the spray drag. Rt is the only one of these quantities that is measured during the model test. The other components require the use of a variety of estimates. In the article, we present specific examples of our approach as applied to a number of tests on surface-effect ship models that we have studied in recent years.
Application of Pull Concept-based Lean Production System in the Ship Building Industry
Authors: Hassan Khairul , Kajiwara Hiroyuki
Published: January 2021

Shipbuilding is a convoluted process. The production system of a shipyard can be illustrated by using the concept of a pull production system. Lean is based on the principle of a pull production system. The shipbuilding process is improved significantly but the lean production system is introduced at very small scales. In a shipyard, different types of wastages such as scraps, overproductions, idle times, etc. are produced, lean is a just-in-time production system that can focus on the elimination of these wastages to ensure lower costs and lower production times and higher quality products as well as better service and delivery. Simulation modeling is used to evaluate the performance of the production system and kanban is a pull-type scheduling method that can be used to simulate the pull production system of a shipyard for the optimization analysis. The goals of this article are to identify the important wastages in a shipyard that can increase production time and cost, to design the production system of a shipyard based on lean philosophy, to derive the basic principles of the lean manufacturing as well as to develop the control mechanism of this production system, the simulation analysis of the production system done by using the lean principle, and to identify the limitations for applying the lean production system in a shipyard production.
Vibration of High-speed Ship Frames
Authors: Davis Michael R. , Davidson Gary , Roberts Timothy , Cato Christopher
Published: January 2021

Impact testing of a typical high-speed ship section has shown that the mode of vibration most likely to fall in the frequency range of excitation resulting from propeller or rotor blade passing is that where the ship frame rocks in a fore and aft direction about its base connection to the hull plate. This vibration has significant amplitude to either side of the keel and it is found that connection between the inboard and outboard sides is weak. As a consequence, vibration can occur in two modes in which the opposite sides of the hull either move together or in antiphase. This leads to the structural strain energy in the two modes being slightly different, the mode with rather less strain energy having slightly lower frequency. Because the frequencies of the two modes are close together, the transient response exhibits beating in which vibration energy is exchanged between the two sides of the hull at the low beat frequency. Vibration of the ship frames in this manner appears to have been the cause of minor weld cracking where the top of stiffeners pass through cutouts in the web of the ship frames within the fuel tank areas of the hull.
Optimum Speed Analysis for Large Containerships
Authors: Khor Yee Shin , Døhlie Knut A. , Døhlie Knut A. , Konovessis Dimitris
Published: January 2021

During these times of fluctuating freight rates and oversupply, selection of optimum speed will give an operator a crucial advantage. Until the recession, the emphasis has always been on larger capacity and higher speed. Now, design innovation and slow steaming are becoming important and this article details new software, which is set up to assist the speed optimization process for large container ships. The software uses both propulsion and revenue-cost analysis with an ultralarge container ship model of 20,000 20-ft.unit (TEU) as a case study to derive the most profitable speed. Shippers' costs are also estimated to assess the impact on shippers. This software can be used for new construction or existing ships. The results show that 19.5 knots is the optimum speed, which is a departure from the current trend of 25 knots but supporting the concept of slow steaming. The results are validated by Det Norske Veritas container cost models. Besides that, the multivariable nature of the optimum speed problem is discussed and further analysis has been carried out to determine the range of fuel cost, freight rate, and load factor in which this optimum speed is applicable (in this case, $1100/TEU < freight rate < $1300/TEU, $650/MT < fuel cost < $750/MT and load factor 1/4 40%). This will be useful to ship operators for forecasting purposes.
Reduction of Welding Distortion for an Improved Assembly Process for Hatch Coaming Production
Authors: Wang Jiangchao , Sano Masanori , Rashed Sherif , Murakawa Hidekazu
Published: January 2021

The alignment between the hatch coaming top surface and hatch cover is essential to maintain hatch cover water tightness and smooth mechanical operation. An improved assembly process for hatch coaming production is proposed, in which the complete hatch coaming is assembled on the shop floor and then lifted as one part, fitted, and welded to the deck. When this complete hatch coaming is assembled to a ship deck, an irregularly distributed gap is usually found between the lower side of the hatch coaming and the deck. Fitting and welding distortion, in particular longitudinal and transverse shrinkage, influence the dimensional accuracy and consequently the production schedule. In this research, welding pass sequence of a fillet welded joint is improved using thermal elastic plastic analysis and welding distortion of the hatch coaming top surface is predicted using elastic analysis. First, three specimens with different gaps that model the welded joint between the hatch coaming and deck were welded and the changed distance between the measuring equipment and the flange was measured. A three-dimensional thermal elastic plastic finite element analysis was carried out for the same specimens and the computed welding distortion was shown to have good agreement with the measurements. As a result of the possible significant influence of welding pass sequence on transverse shrinkage of a fillet welded joint, the influence of welding pass sequence is studied using the computational approach and improved welding pass sequences are proposed to reduce transverse shrinkage. Finally, elastic analysis using inherent longitudinal and transverse shrinkage deformations evaluated by thermal elastic plastic analysis is used to predict welding distortion of the hatch coaming. In this elastic analysis, the influence of different gaps at different locations between the hatch coaming and the deck is considered.
Study of a Novel Air-augmented Waterjet Boost Concept
Authors: Gany Alon , Gofer Aviad
Published: January 2021

This research presents analysis, experiment, and prediction of the performance of a unique marine propulsion concept, the air-augmented waterjet, having a revolutionary potential for significant thrust augmentation and boost capability of waterjet systems. So far, this concept has not been realized in any operational vessel. The air-augmented waterjet propulsion concept is similar to an after-burner in the aeronautical turbojet engine. The thrust augmentation results from the injection of air bubbles into the water flow, converting their expansion work òpdV into additional kinetic energy of the exhaust jet without affecting the pump operation. It can enable substantially augmenting boost capability, overcoming hump resistance, and increasing maximum attainable vessel speed while avoiding cavitation problems. Static tests at the Technion's water tank, using a jetski waterjet engine of a nominal power of 50 kW, have been conducted with and without air injection over a range of motor revolutions per minute (rpm). The addition of air increased the thrust by 20% to 50% depending on the airflow rate and engine rpm. Air expansion work increased the exhaust jet kinetic energy at an efficiency of 70% approximately. Based on the static experiments, prediction of the system behavior for different vessel speeds and engine power levels has been made, revealing a higher relative thrust augmentation for the same pump power and airflow rate at higher vessel speeds. The air-augmented waterjet concept may add a new dimension to marine propulsion as well as upgrade existing vessels.
Experimental Investigation of Trimaran Models in Shallow Water
Authors: Pavkov Mark , Morabitob Morabito
Published: January 2021

Experiments were conducted at the U.S. Naval Academy's Hydromechanics Laboratory to determine the effect of finite water depth on the resistance, heave, and trim of two different trimaran models. The models were tested at the same length to water depth ratios over a range of Froude numbers in the displacement speed regime. The models were also towed in deep water for comparison. Additionally, the side hulls were adjusted to two different longitudinal positions to investigate possible differences resulting from position. Near critical speed, a large increase in resistance and sinkage was observed, consistent with observations of conventional displacement hulls. The data from the two models are scaled up to a notional 125-m length to illustrate the effects that would be observed for actual ships similar in size to the U.S. Navy's Independence Class Littoral Combat Ship. Faired plots are developed to allow for rapid estimation of shallow water effect on trimaran resistance and under keel clearance. An example is provided.
Study on Plate Forming Using the Line Heating Process of Multiple-torch
Authors: Zhou Bo , Han Xiaoshuang , Tan Soon-Keat , Liu Zhong-chi
Published: January 2021

With increasingly competition in the world shipbuilding market, manual and experiential technique patterns of line heating process could not meet the requirements of modern shipbuilding in product speed and quality. In recent years, the improvement of productivity for line-heating process is one of the goals in the shipbuilding industry, which means an accurate prediction model is very important. In this study, a finite element analysis (FEA) model for the line-heating process was established and experiments were conducted to prove the validity of the model. The final numerical results are in good agreement with experiment results. Based on the FEA model, the feasibility of the multiple-torch process is verified. The multiple-torch process could greatly save processing time, which is entirely feasible in the specific automation implementation. Finally, the effect of heat line spacing is analyzed, which could provide important information for the line-heating process design. The proposed method presents a valuable reference for the study of the similar thermal process.
Modeling with Regression Analysis and Artificial Neural Networks the Resistance and Trim of Series 50 Experiments with V-Bottom Motor Boats
Authors: Radojcic Dejan V. , Morabito Michael G. , Simic Aleksandar P. , Zgradic Antonio B.
Published: January 2021

Mathematical representations for the resistance, trim, and wetted length of the Experimental Model Basin Series 50 have been developed using conventional regression analysis techniques as well as artificial neural networks. Series 50 is a standard series of 20 V-bottomed motor boats tested in 1941. These hulls could be representative of today's semidisplacement hulls. Recently, the series has been reanalyzed and published using contemporary planing coefficients, enabling resistance prediction in design stages. In the present study, mathematical representations are developed for the Series 50 as an alternative to using charts or data tables. Two methods are used, regression analysis and artificial neural networks. This study provides a useful resistance prediction method for designers and an opportunity to compare and contrast regression analysis and artificial neural networks applied to standard series. The main finding of the study is that both techniques were capable of developing stable and accurate models. A detailed quantification of the differences between methods is provided.
Reduction of Overwelding and Distortion for Naval Surface Combatants, Part 1: Optimized Weld Sizing for Lightweight Ship Structures
Authors: Huang T. D. , Harbison Michael , Kvidahl Lee , Niolet David , Walks John , Stefanick Kevin , Phillippi Mark , Dong Pingsha , DeCan Larry , Caccese Vincent , Blomquist Paul , Kihl David , Wong Rick , Nappi Natale , Gardner James , Wong Catherine , Bjornson Michael , Manuel Allen
Published: January 2021

As high-strength thin-steel use in ship design increases, dimensional management becomes critical to control construction costs and schedule in ship production. In the U.S. shipbuilding industry, improvements to shipbuilding facilities and processing technology have not kept pace with the rate of change in ship design. Additionally, new designs using thinner steels are subject to legacy weld-sizing criteria, which may inappropriately size welds on lightweight materials. These two factors result in widespread overwelding, causing severe plate buckling in naval vessels during construction. The problem of overwelding has two distinct sources:the weld-sizing methods developed in the 1980s are still used in most shipbuilding specifications regardless of ship class. This prevents the incentive of application of latest technologies that can make strong, precision fillet welds for modern lightweight thin steel naval surface combatants; andshipyard welders tend to make welds even larger than design requirements to satisfy naval production specifications, which do not allow for any undersized welds.

On average, production welds are 3 mm larger than design, which can more than double the heat input and distortion caused by welding. The approach to the solution of this overwelding problem will be described in detail in this article:develop appropriate weld-sizing criteria for thin plate structures; this can be facilitated by numerical modeling to ensure adequate static shear, tensile, bending, fatigue, and dynamic impact capacity of structural welds; andperform a robust designed experiment to establish confidence that small weld sizes can provide necessary performance and strength to meet the design service life of the vessel and provide data to NAVSEA technical warrant holders to support the implementation of an underweld tolerance for ship production to prevent overwelding.
A Contribution to the Identity Assessment of Ship Structure Plate Parts
Authors: Hmeshah Khaldoun , Bronsart Robert
Published: January 2021

For the modeling of the ship structure, computer-aided design systems are generally used. During the different phases of the ship structure modeling and production process, the correctness of the generated product model data has to be continuously preserved. The correct assignment of position numbers to steel parts, e.g., represents a fundamental requirement of the ship structure production management. According to this requirement, a quality criterion can be formulated, that all parts to be manufactured have to have a position number assigned to with the condition that only identical parts should have the same position number. Two parts are generally regarded to be identical when they have the same properties concerning material, thickness, and shape. Shape in this case includes the outer and the inner contours (holes). The current control mechanisms of the correctness of product model data are manual, drawings-based methods. A new approach has been developed to automatically check the identity of the ship structural parts already during the design phase. This mechanism allows the engineers to maintain the quality of the product model data before it will be handed on for further processing. The approach described in this article is based on the Fre´chet distance algorithm, which is generally used to assess how closely two continuously closed curves resemble each other. The results of the steel structural parts shape comparison are presented in a report. This report can be used to check the correctness of the position number assignments and by this contributes to the overall quality assurance mechanism to preserve a high quality of the product model data. Although errors can be avoided, which will otherwise be detected in later process phases, they have to be fixed with significant additional costs.
On the Prediction of Wave-added Resistance with Empirical Methods
Authors: Grin Rob
Published: January 2021

There is continuous research on analytical, numerical, and (semi)empirical methods to predict wave-added resistance. Most of this research focuses on a particular area, like motion-induced wave added resistance, wave-added resistance in short waves, or is limited to head seas only. The practical application of most methods is therefore often limited. Moreover, most methods require detailed information on hull lines and results are rather sensitive to the discretization of those hull lines. Since 2006, MARIN has been investigating the feasibility of empirical methods that do not have those limitations. They only require the main particulars to predict wave-added resistance. Within the Sea Trial Analysis Joint Industry Project (STA-JIP), a method was developed for the correction of wave-added resistance in head seas covering both the motion-induced and the wave reflection-induced component. This method was further refined and extended to all wave directions within the service performance analysis JIP (SPA-JIP) in 2008. This article presents the results of the comparison between the prediction methods and model tests for almost 50 different ships, comprising more than 1500 tests in regular and irregular seas.
Foreign Shipyard Coatings Benchmarking Study
Authors: Kattan Raouf , Broderick Darren , Cogswell Steve , Blakey Judie , Ault Peter
Published: January 2021

U.S. yards have undertaken benchmarking studies under the auspices of the national Shipbuilding Program for many years (FMI 2001). However, little emphasis has been placed on the coating process. During that time, management of the coating process has increasingly become problematic at new construction, in particular as a result of the relative increase in labor content, the increased regulatory and environmental burdens, and the impact on the build schedule and strategy of what is often a bottleneck process.
Reduction of Overwelding and Distortion for Naval Surface Combatants. Part 2: Weld Sizing Effects on Shear and Fatigue Performance
Authors: Huang T. D. , Harbison Michael , Kvidahl Lee , Niolet David , Walks John , Christein J. P. , Smitherman Mark , Phillippi Mark , Dong Pingsha , DeCan Larry , Caccese Vince , Blomquist Paul , Kihl David , Wong Rick , Sinfield Matthew , Nappi Natale , Gardner James , Wong Catherine , Bjornson Michael , Manuel Allen
Published: January 2021

As high-strength thinner-steel implementation in ship designs increase, dimensional management becomes critical to control construction costs and schedule in ship production. In the U.S. shipbuilding industry, improvements to shipbuilding facilities and processing technology have not kept pace with the rate of change in ship design. Additionally, new designs using thinner steels are subject to legacy weld sizing criteria possibly leading to inappropriately sized welds on lightweight materials. These two factors result in widespread overwelding, causing severe plate deformation in naval vessels during construction and nonvalue added labor to correct as needed for fit-up tolerances. Historically, shear and fatigue strength data has been focused on the larger welds and thicker steel plates typical of the state of the practice when these legacy weld sizing criteria were developed. In order to optimize weld design and production in modern, lightweight naval surface vessels, there is a need to develop more accurate data about the performance of precision fillet welds for thin steels.
Research of the Curve Radius of Shape Formed in Profile Cold Forming with BP Neural Networks Approach Based on Experiment
Authors: Peiyong Li , Feng Gao , Chengfang Wang , Yunsheng Mao , Jin Cui
Published: January 2021

During the processing of frame part forming in ship production, the prediction of the curve radius of shape formed is of great significance for the quality and efficiency of forming work. The experiment method is used to conduct the research. Because the profile forming is affected by various factors, this article used orthogonal experiment designing method to draw up the forming experiment scheme. In the experiment researches, the angle steel is chosen as study object. Using the data recorded in the experiments as training sample, this article established a model based on the Bayesian regularization back propagation (BP) neural network to predict the curve radius of shape formed. With this model and the test sample recorded in the experiment, the calculation results showed that the model could reflect the relationship between the technical parameters and the curve radius correctly. Using the above model, this article predicts the curve radius with a series of variables of the influence factors, studies the rules of the influence of the factors to the curve radius, and obtains meaningful conclusions. These conclusions have been applied to guide the development of the three-fulcrum frame bender successfully.
Understanding and Optimizing Vessel Propulsive Power and Fuel Use Using Duty Cycle Analysis Computations
Authors: MacPherson Donald , Boyd Elizabeth
Published: January 2021

The maritime industry is in a mind-set to save fuel and reduce emissions. How one achieves this end, however, can be a matter of some debate. Although substantial industry effort is being placed on things that can be optimized, to achieve real benefit and financial return one must first understand the details about how the vessel consumes propulsive energy during its mission. This article discusses a rational, simple, and effective systems engineering approach to identify power and fuel demands via computational propulsion analysis of the individual operating modes of a vessel's duty cycle. It explains sensible consumption metrics that can be used to evaluate and compare different physical systems, strategic plans, or helm decisions. A duty cycle operating mode analysis calculation for a tugboat in multirole service (as a harbor tug and in long haul ocean barge towing) is demonstrated using commercial off-the-shelf software, including examples of design-side and shipboard decision options and consequences.
Study on the Safety Degree of Ship Capsizing in Stochastic Waves
Authors: Zhang Jianwei , Wu Wanqing , Hu Junquan
Published: January 2021

To quantify ship capsizing, from the energy perspective, the safety degree of a ship in waves is estimated based on stochastic Melnikov function and phase space transport theory. Considering the influence of nonlinear damping moment, nonlinear restoring moment, as well as the random waves, a nonlinear single degree of freedom differential equation for ship rolling is established. Transform the random wave moment from time domain to frequency domain by fast Fourier transformation, the random Melnikov function and rate of phase flux are extended to include the effects of navigation speed and heading angle and the safety degree of ship capsizing is quantified according to its statistical characteristics. Through an example, the accuracy of Melnikov function and phase space transport theory are verified and the effects of ship speed and heading angle on phase space transport rate are also quantified. This method is demonstrated properly to quantify the safety degree of ship capsizing and some valuable reference can be provided for the further research on ship stability criteria.
Weld Residual Stress Measurement on Ship Structures
Authors: Yang Yu-Ping , Huang T. D. , Scholler Steve , Dull Randy , Fisher Charles R. , Zhang Wei
Published: January 2021

Weld residual stresses on ship structures were significantly investigated by using a three-step approach. Step 1 is to measure residual stress on small samples in laboratories to validate measurement methods, step 2 is to measure residual stress on three test panels made of DH36, HSLA-65, and HSLA-80 in a shipyard, and step 3 is to measure residual stress on a large mock-up unit and on a tie-down. Step-1 and step-2 study, presented in the Society of Naval Architects and Marine Engineers-2017 conference, concluded that portable X-ray equipment can be used in a shipyard environment to provide reliable measurements. Residual stress was successfully measured on small welded joints, the DH36 panel, and the HSLA-65 panel, but not on the HSLA-80 panel. The reason for poor measurements on the HSLA-80 panel was that the primer on HSLA-80 surfaces blocked the diffracted X-ray. To achieve a good measurement, mechanical grinding and electropolishing were investigated to remove the primer before measurement. The minimum electropolishing time required to remove the compressive stress induced by mechanical grinding was established by experimental trials. With the electropolishing process, reasonable measurements were achieved on the HSLA-80 panel, a tie-down, and the knuckle joints of the large mock-up unit. This study reports the measured stresses on the HSLA-80 panel, the tie-down, and the knuckle joints.

Welding, as one of the most important manufacturing processes in shipbuilding, inevitably induces residual stress and distortion on ship structures. Multiple methods have been developed to measure residual stress with nondestructive and destructive techniques. The common nondestructive techniques include X-ray diffraction (XRD) (Gou et al. 2015; Bandyopadhyay et al. 2018; Monine et al. 2018), neutron diffraction (Palkowski et al. 2013), magnetic method, ultrasonic methods (Bray & Junghans 1995), and impact-indentation method (Zhu et al. 2015). The destructive techniques include hole-drilling and ring-core methods, and the destructive techniques include block removal, splitting, layering, and contour methods (Leggatt et al. 1996).
Smart Bearing Sensor
Authors: Leontopoulos Chris , Mouzakis Charalampos , Petrolekas Michail
Published: January 2021

The recent increase in vessel shaftline bearing incidents indicates that a static shaft alignment design may not be suitable for all operational shaftline loading conditions. Hull deflections caused by vessel loading or propeller loads initiated by interaction with the wakefield have become important considerations in modern vessel design. Jack-up tests, typically used as a bearing load verification method, can only be accomplished under static shaft conditions and cannot verify the shaft dynamic behavior under running operational conditions. A newly developed sensor using strain gauge technology measures the bearing load and the shaft misalignment angle through the bearing housing's deformation-induced strain. It effectively converts the bearing housing into a weighing machine by mapping the bearing housing strain onto the bearing load. Unlike jack-up tests, this method allows for the continuous measurement of the bearing load and misalignment angle under all shaftline operational conditions. It is envisaged that this technologically simple system will allow for the earliest possible diagnosis of shaft alignment-related problems, such as bearing unloading, bearing overloading, or excessive shaft-bearing misalignment. This provides a much earlier warning indicator when compared with the bearing temperature alarm. The subject technology has been tested on intermediate bearings and is considered for future application into stern tube bearings.

1. Introduction

In post-IMO's (International Maritime Organization) Energy Efficiency Design Index vessel designs, the propulsion shafting arrangements become increasingly sensitive to shaft alignment with lower tolerances and margins, increasing the risk of stern tube bearing failures (Leontopoulos 2016a). This change is due to the wider use of more efficient, larger diameter propellers with increased cantilevered load on the shafting system and shorter shaftlines as a result of maximizing cargo space and minimizing engine room length. Widespread application of the single stern tube bearing design (an arrangement without a forward stern tube bearing) has also highlighted a decreased tolerance to eccentric propeller thrust and propeller forces in general. Reduced tolerance to shaft alignment sighting errors, bearing offset inaccuracies and other shaft installation errors, also affects the integrity of the shafting system and can result in complete bearing wiping with the consequence of vessel propulsion immobilization. This undesirable consequence has increased, particularly during the years 2013–2017.
Development of an IHOP Execution System Based on Analyses of Shipyard Production Planning Process
Authors: Lee Kwangkook , Shin Jong Gye
Published: January 2021

Production management in shipyards is one of the most significant activities impacting productivity. On-site managers and production planners still do not have sufficient production information to enable on-site scheduling because of restricted information sharing among departments. In this research, the main production management challenges were determined from workflow simulations of the production planning processes. An analysis of the requirements for effective communication between production management and on-site personnel was undertaken to establish an integrated hull construction, outfitting, and painting execution system architecture for shipyard applications, developed following the component-based design methodology. The proposed systems key functions encompass stages from block assembly to hull outfitting at the quay, and enable visualization of the production progress through color differentiation to maximize production information sharing. The proposed system facilitates the transmission of reliable and accurate production information to all relevant personnel in an appropriate timeframe.
Buoyancy Effect on Natural Frequency of Vertical Modes of Hull Vibration
Authors: McGoldrick R. T.
Published: January 2021

While the inertia effect of the surrounding water is known to be very large, and is always taken into account in calculating the natural frequencies of hulls, the buoyancy or elastic effect invariably is neglected. Thus the hull is actually treated as free in space with a distributed mass added to account for the effect of tile water.
What the Society Is Doing to Advance Its Ship Research Program
Authors: Jones Klemme M.
Published: January 2021

Wide activity in solving the problems of ship and machinery design reported by Research Committees and Panels of The Society of Naval Architects and Marine Engineers