The Development of Log Aesthetic Patch and Its Projection onto the Plane

In this work, we introduce a new type of surface called the Log Aesthetic Patch (LAP). This surface is an extension of the Coons surface patch, in which the four boundary curves are either planar or spatial Log Aesthetic Curves (LACs). To identify its versatility, we approximated the hyperbolic paraboloid to LAP using the information of lines of curvature (LoC). The outer part of the LoCs, which play a role as the boundary of the hyperbolic paraboloid, is replaced with LACs before constructing the LAP. Since LoCs are essential in shipbuilding for hot and cold bending processes, we investigated the LAP in terms of the LoC’s curvature, derivative of curvature, torsion, and Logarithmic Curvature Graph (LCG). The numerical results indicate that the LoCs for both surfaces possess monotonic curvatures. An advantage of LAP approximation over its original hyperbolic paraboloid is that the LoCs of LAP can be approximated to LACs, and hence the first derivative of curvatures for LoCs are monotonic, whereas they are non-monotonic for the hyperbolic paraboloid. This confirms that the LAP produced is indeed of high quality. Lastly, we project the LAP onto a plane using geodesic curvature to create strips that can be pasted together, mimicking hot and cold bending processes in the shipbuilding industry.

Analysis of Hull Shape Impact on Energy Consumption in an Electric Port Tugboat

The trend to replace internal combustion engines with electric zero-emission drives, visible in the automotive industry, also exists in the shipbuilding industry. In contrary to land vehicles, the requirements for the electric propulsion system of tugs are much greater, which combined with the limited space and energy on board, makes any amount of energy valuable. Strategic changes in the policy of many countries, such as the “Fit for 55” package, introduce plans to significantly reduce CO2 emissions, which favors the development of alternative drives and their introduction to new areas of operation. This article presents that it is possible to reduce the amount of energy an electric tug spends for movement by applying the Particle Swarm Optimization method to modify the shape of its hull. A statistical analysis of public data was performed to determine the speed profiles of actual port tugs. The Van Oortmerssen method was used to determine the hull resistances of the proposed tug and the impact of the hull shape modification sets on reducing these resistances. Based on the six obtained speed profiles, it was determined that one of the tested variants of modifications made it possible to reduce energy consumption on average by 2.12%, to even 3.87% for one of the profiles, and that some modifications increase energy consumption by even 6.59%.

Stiffener Design to Maintain Line Heating Efficiency during the Lifting Process Considering Phase Transformation

In the shipbuilding industry, welding is the main technique used to join steel structures. There is a lifting process, post-welding, that can eliminate the correction effect of line heating. Line heating is reperformed after the lifting process. This can significantly delay the ship assembly process. Herein, we present a design method for installing a permanent stiffener to avoid the disappearance of the line heating effect during the lifting process. The change in physical properties due to heating and cooling of the line heating is calculated. The limiting stress, at which the effect of the line heating completely disappears, based on the inherent strain theory, is obtained. The phase fraction by the cooling rate is calculated using the continuous cooling transformation diagram and the Kiustinen–Marburgerm equation. Physical properties affected by the phase transformation are calculated, considering the physical properties and fraction of each phase. The square plate theory and superposition principle are used to construct a local model, with a stiffener, of the ship block. The stress caused by the shape of the stiffener and the distance between the stiffeners were calculated for the local model. The calculated stress and the limiting stress were compared to determine, for the expected line heating efficiency, the most acceptable stiffener design. Finally, to confirm the elimination of the problem, the designed stiffener is analyzed using the finite element method.

Methodology for composite materials shrinkage definition for use in shipbuilding and marine technology

Deformations of steel material in shipbuilding and marine technology applications as a result of mechanical or temperature influences are a well-known problem. However, in the modern shipbuilding industry, the application of alternative materials, especially composite materials, in the structure and for the equipment of the ship is increasingly represented. Consequently, there is a need to determine the deformation and change of characteristics of such composite materials as a result of various mechanical, and especially temperature influences that cause the so-called shrinkage. The basic composite production process involves connecting the matrix with a catalyst and accelerators that create temperature, then the material shrinks by cooling when it can change its dimensions and characteristics. Also, in order to achieve the best possible mechanical properties, composite materials are specially heated and then cooled according to strictly defined processes and curves. The ability to predict the characteristics and parameters of such deformations is important in the context of the application of composite materials. To define such deformations, different methods are used within individual numerical solvers, whose results can differ significantly from each other. Therefore, the authors in this paper present an established methodology for predicting mechanical and temperature deformations, and modelling of composite materials, based on the analysis of analytical methods and numerical solvers with the aim of defining the most accurate numerical solver. By applying the presented methodology, it is expected to raise the level of accuracy and quality of composite materials production as well as to raise the quality of design solutions and efficiency of production procedures during shipbuilding in particular, but also within different marine technology applications and during the product’s life cycle.

Experimental Research On The Technology of Two-Pass Different Temperature Rolling For Thick Steel/Aluminum/Aluminum-Alloy Composite Plate

Thick steel/aluminum/aluminum-alloy composite plate is one of the key materials connecting steel structures and aluminum alloy structures, and has been widely used in shipbuilding industry and other fields. However, steel/aluminum/aluminum-alloy composite plates with a total thickness of more than 10 mm and a steel layer thickness of more than 5 mm are prone to problems such as inconsistent deformation of component metals and low bonding strength during the rolling process, and cannot be continuously prepared. In order to solve this problem, this article proposes a two-pass different temperature rolling process for thick steel/aluminum/aluminum-alloy composite plates, and conducts research on Q235B steel, 1060 aluminum and 5083 aluminum alloy as component metals. The results show that the process is reliable. It can prepare Q235B/1060/5083 composite plates with a thickness of 15.65 mm without oxygen protection measures. Meanwhile, the interfacial shear and pull-off strength of the composite plates obtained under different experimental conditions in this article are higher than the requirements of the US military standards MIL-J-24445A and Chinese ship standard CB20091-2012. And the composite plates showed good performance in 90° and 137° bending tests without obvious defects. Under the best condition of them, a 1.48 μm interlocking diffusion layer was formed at the steel/aluminum interface of the composite plates, and the interfacial shear strength exceeded 70 MPa, and the interfacial pull-off strength exceeded 110 MPa. Finally, according to the experimental results, the reasons for the feasibility of the two-pass different rolling of thick steel/aluminum/aluminum-alloy composite plates are given.

Assessment of environmental pollution level caused by shipbuilding industry

The purpose of the paper was to create databases that would allow a proper assessment of the degree of marine pollution generated by the shipyard industrial sector. The study was conducted over a period of three years, between 2015 and 2017. The parameters determined for the waters collected from the shipyard were within the maximum allowed limits according to the norms in force. However, values very close to the maximum allowable limit were observed in the case of groundwater for nickel, determined from the drilling located near the fuel depot in 2015 and chlorides determined from the drilling located near the galvanizing workshop, both in 2016 and in 2017. The analyzed parameters for the soil samples, collected from various sampling points and different depths, were below the value of the alert thresholds for less sensitive soils, according to Order 756/97. The databases created for this study can contribute as an incipient basis for the development of larger studies that include other industrial sectors as well as a longer evaluation period.

ASSEMBLY LINE BALANCING IMPLEMENTATION IN MINOR AND SUB ASSEMBLY WORK SHOP AT SHIPYARDS

Recently, the competitive environment is very tough in shipbuilding industry and under these circumstances, manufacturing a ship in a shorter time becomes significantly important in order to meet the customer demands. Therefore, it is hard to do that by using traditional manufacturing techniques. The shipyards located in Turkey usually have functional locations for the machines and this situation often causes longer production times. Instead of this, assembly lines should be redesigned as workshops in the shipyard. Prefabrication work unit is a good example in which an assembly line is needed to be designed. In this study, an assembly line design for prefabrication work unit was performed. For this, assignments of work operations to work shops were carried out by using Largest Set Rule Algorithm and some alternatives were created according to compare the different values of cycle time. These alternatives were simulated by using a production simulation program and the most appropriate assembly line design was presented.

WORK ANALYSIS OF PLATE BENDING WORKSHOP IN SHIPBUILDING INDUSTRY

Plate bending is one of the major processes in shipbuilding. The plates which are cut in specific dimensions are sent to plate bending work shop and they are curved by using various methods. These curved plates constitute bilge turn plates of a vessel which are curvilinear. In this study, plate bending work shop was considered and its simulation model was created by using SIMIO software. The aim of the study is to see the effects of some alterations on available situation of plate bending work shop and present some recommendations in order for the plate bending work shop to operate effectively. In this work, there are number of four alterations including the changing of bending processing time, number of cranes and bending machine. At the end of the study, the values of the most suitable crane number, bending machine number, and the bending operation processing time were recommended. It is believed that the plate bending work shop will operate in effective way if the shipyard administration implement the recommendations presented in this study.

INVESTIGATION OF WELDER SELECTION PARAMETERS BASED ON FUZZY ANALYTIC HIERARCHY PROCESS IN SHIPBUILDING

Today, it is very significant to select appropriate welders in shipbuilding industry. The fact that there is a really tough competition between shipyards triggers the increasing of welder quality. Higher welder quality means higher quality welding workmanship. If a shipyard has a high quality workmanship, it has bigger competitive power than its rivals. Therefore, shipyard management must take welder selection into more consideration. In this study, the weights of welder selection parameters of shipyards were determined by utilizing Chang’s extent analysis method. In this way, it is aimed to understand the point of view of shipyards in selecting welder. In addition, taking into account the important parameters in welder selection, the welders can improve their weak sides. Consequently, the results obtained from this study are believed to be a guide for the people who want to work as a welder in shipyards.