Aluminum Hull Research Articles

Impact Analysis of Welding Sequence to Reduce Weld Deformation in Aluminum Hulls

Aluminum hulls, which are preferred in the marine industry due to their durability, corrosion resistance, and lightweight properties, face serious challenges due to thermal deformation during welding. This study aims to predict and minimize transverse deformations due to welding sequences for a transverse model in the lower part of an aluminum hull. To predict deformations, heat source dimensions obtained from actual weld beads were used as simulation conditions, and various welding sequence conditions were simulated through the developed finite element method (FEM). The simulation results were compared with actual deformation measurements to verify their reliability, and the optimal welding sequence which minimized deformation was derived. The simulation results show that by changing the welding sequence conditions, the maximum displacement can be reduced from a maximum of 52.1% to a minimum of 39.1%, and the effective plastic strain can be reduced from a maximum of 19.6% to a minimum of 4.8%. These results show that adjusting the welding sequence conditions can significantly improve structural integrity by minimizing deformation. The results of this study suggest that the control of the welding sequence can be used to reduce the deformation of aluminum hulls and promote a more sustainable marine industry with improved quality.

Experimental Study of Aluminium Joint Plate Between AA5052 with AA5083: Application on Hull Vessel Material

Generally, the planning of the material arrangement of the aluminum hull plate is always carried out at an early stage to obtain a material formation that has good economic value. One of the strategies used to obtain economic value in shipbuilding is the use of various grades of plate material. The grade of aluminum material that is often used on ships is the 5xxx series. Where this series has many grades that can be used as ship hull material options. The price difference for each grade of aluminum material for ships is a very influential variable on the economic value of shipbuilding. However, before being applied to shipbuilding, it is necessary to test the feasibility of aluminum plate connections with variations in plate grade. The aim is to provide clear information regarding the technical feasibility of selecting material grades. Therefore, in this study, a simulation will be carried out to test the strength of the plate connection with variations in the grade of aluminum material using the experimental method. The plate joint test is carried out using only the Tensile test in the laboratory with reference to the ASTM rules. The grades of aluminum plate materials used are 5052 and 5083. Connection formations are between 5052-5052, 5083-5083, and 5052-5083. From the test results, the largest average yield stress value is 202.34 N/mm 2 at the variation 5083-5083, the maximum average ultimate stress value is 261.70 N/mm 2 at the variation 5083-5083. For the variation of the 5052-5083 plate connection, it still has a yield stress value that is greater than the basic yield stress of the material, namely 142.97 N/mm 2 . Where the percentage value of the achievement level of yield strength is 113.6% of the basic yield stress value of the material based on BKI rules. However, in achieving the ultimate stress value, it is still lower than the ultimate basic stress of the BKI rules standard material, which is 193.88 N/mm 2 . Where the percentage value of the level of ultimate strength achievement is 70.5% of the ultimate basic stress value of the BKI rules standard material.

Material Effectiveness Model for the Construction of Aluminum Hull

Construction of a hull generally requires several plates and profile material. Early indications for shipbuilding indicate that in manner, the linear function approach for installed material was 75% to 90%, and waste material was 10% to 25%. This study is conducting an assessment of the area of installed material and waste material on small vessels made of aluminum with variations in ship length and the method of approach trend lines both linear and nonlinear. Secondary data retrieval in the form of an aluminum cutting plan for plate material and profile from the AutoCAD application, which is then reprocessed through the FastCAM application to obtain results in the form of identification of installed material and waste material area. Based on variations in ship length and material area results, a scatter plot process was carried out through the Excel application to obtain results in the form of trend line functions with an R-squared determination coefficient of more than 0.9 and the results of the calculation of the intersection between the function of installed material and waste material, and the waste material function with the x-axis uses the balance method. The final result showed that the linear function gives an indication of the effectiveness of the material located in the range of 6 to 23 meters in length of the boat and polynomial function of order 2 in the range of 6 to 18 meters in length, while the waste material area in the two functions maximum 22%.

Determination of corrosion protection current density requirement of zinc sacrificial anode for corrosion protection of AA5083-H321 in seawater

In this study, the current density requirements of zinc sacrificial anode for corrosion protection of AA5083-H321 aluminum hull for the ship was determined through various electrochemical tests. Surface observation and chemical composition analysis were performed after the galvanostatic test for various current density requirements determined by the cathodic polarization experiment. As a result, the most appropriate current density requirement range was determined as 3.7 × 10−6–5.8 × 10−6 A/cm2. Excessive current density over 7.6 × 10−6 A/cm2 caused local surface damage due to the effect of Mg-rich and Fe-rich intermetallic phases. In addition, the self-consumption of zinc sacrificial anode was determined through Tafel's extrapolation method.

Parametric study of buckling and post-buckling behavior for an aluminum hull structure of a high-aspect-ratio twin hull vessel

Metal plates are essential parts of structures such as ship hulls and offshore oil platforms. These plates are typically under compressive axial forces. Hence, one of the main mechanisms for failure and collapse of such structures is buckling of plates. Thus, for safe and secure design, buckling strength of plates should be evaluated. Finite element analysis techniques are perfect tools for this purpose because of the accuracy and flexibility for performing simulations with different variables. In this study, the strength of aluminum plates has been studied using finite element analysis software and it was tried to study the influence of variables such as initial imperfections, plate thickness and aspect ratio on plate strength. It was found that increase in the imperfection magnitude leads to a decrease in the strength of the plate. This is mostly noticed in thin plates because of the plate’s stiffness reduction. Although the plate’s aspect ratio has a slight effect on strength, it has a considerable impact on the failure mechanism. In order to study a combination of plates and stiffeners buckling behavior, part of a high-aspect-ratio twin hull vessel hull structure is assessed under bending moment. It is observed that longitudinal stiffeners at the bottom of the hull in linear analysis undergo the maximum stress, while in non-linear analysis, the maximum stress is spread along with the structure of the deck and bottom, and neutral axis tolerates the minimum stress.

Development and Experimental Tests of a ROS Multi-agent Structure for Autonomous Surface Vehicles

Robotic structures that couple autonomous surface vehicles and unmanned underwater vehicles in integrated systems with various levels of cooperation provide interesting solutions to the problem of developing efficient, versatile and cost effective tools for exploration, monitoring and exploitation of the underwater environment. In this paper we describe the development and preliminary field testing of an autonomous surface vehichle that can automatically track, deploy and recover a small remotely operated vehicle, which is guided from a shore-ground station. This goal is achieved by exploiting two-ways transmission of data and commands through the umbilical and a wireless link with a shore-ground station. In this way, pilots can experiment telepresence in the underwater environment, avoiding the need of expensive and logistically demanding manned supply vessel. The vehicle is a small aluminum hull boat, equipped with a steering outboard electric motor. A multi-agent system in the ROS framework is proposed for the robotic structure. The use of commercial-off-the-shelf components and the choice of a multi-agent ROS architecture are a mean to reduce costs and to assure performances, modularity and versatility. Field tests in both supervised and autonomous guidance mode have been performed in order to assess the basic functionalities of the system and their results are illustrated and discussed.

Effect of fabrication methods on the ultimate strength of aluminum hull girders

A three-dimensional nonlinear finite element model was developed to simulate the welding process of extruded and non-extruded aluminum tee-bar stiffened plates joined together by friction stir welding (FSW), metal inert gas (MIG) butt and MIG fillet welding. The three-dimensional residual stress and distortion fields as well as the heat affected zones (HAZ) for all three welding methods were obtained and compared. The load-shortening curves for stiffened plates and the ultimate moment capacity of a hull girder made up of the stiffened plates were analyzed. The results showed that MIG welding resulted in tensile and compressive residual stress of as much as 88% and 30% of the material yield strength, and a considerable level of distortion while residual stresses and distortions formed in the friction stir welding model were negligible. The load-shortening responses showed that extruded stiffened plates joined by FSW attained a 26% higher buckling load than the non-extruded stiffened plates joined by MIG fillet welding, which in turn resulted in a 28% higher ultimate moment capacity of the hull girder fabricated using FSW on extruded elements. The results also indicated that the presence of the residual stress and HAZ had the most significant effect on hull girders fabricated by MIG fillet welding on non-extruded plates where respective reductions of 10.5% and 7.5% in the ultimate moment capacity of the hull girders as a result of residual stresses and HAZ were observed.

On structural design of energy efficient small high-speed craft

This paper presents an integrated design procedure for determination of structural arrangement and scantlings for the complete structure of small high-speed craft. The purpose of the procedure is to serve as a tool in the preliminary design stage where it enables generation of weight minimized designs with very limited effort. The design procedure is applied in a material concept study for a high-speed patrol craft. The various concepts include single skin and sandwich composites, aluminum and steel. It is demonstrated that the mass of the aluminum hull structure can be reduced from the original 11.7 tonnes to 9.6 tonnes through application of the presented design procedure. The most weight efficient material concept is a carbon-fiber foam-cored sandwich with a structural mass of 4.8 tonnes, which is about 50% less than the refined aluminum version. Through simple hydromechanic analysis, potential for fuel and CO2 emission reductions of 8% for the refined aluminum version and 27% for the carbon-fiber sandwich version in relation to the original craft are indicated.

Settlement and potential for transport of clubbed tunicate (Styela clava) on boat hulls

The invasive clubbed tunicate (Styela clava) was first identified in Georgetown harbor, Prince Edward Island (PEI), Canada, in 1998 and has since spread to other estuaries in PEI. Worldwide, the dispersal of this species is attributed to hull fouling and contamination of bivalve aquaculture products. We tested how clubbed tunicate settlement patterns differed among the most common boat hull surfaces and colors as well as the ability of these tunicates to survive extended atmospheric exposure similar to that of boats being transported on trailers during summer months. Untreated hulls made of fiberglass, painted wood, and bare aluminum were quickly colonized by larval tunicates with hulls painted black attracting significantly more colonists compared to white-painted hulls. Use of anti-fouling paint kept colonization to a minimum, even after 12 weeks in the water. Bare aluminum hull material attracted the highest numbers of tunicates, which is a problem because boats operating around bivalve aquaculture sites are mainly constructed of aluminum and cannot be painted with anti-fouling paint according to industry codes of practice. Aluminum and fiberglass hull material that had one-year-old tunicates growing on them were exposed to open air for 48 h during September (mean daytime high temperature 29.7˚C, night-time low 8.5˚C). Nearly all tunicates were alive after 8 hours with only 10 to 11 % mortality after 48 h. Based on a 48 h survival time, viable tunicates on boats removed from infested waters of PEI could be spread on boats transported on trailers to any waters within 1600-2000 km of PEI – a distance encompassing the entire Atlantic seaboard of Canada.

Segurança das condições de aplicação de herbicidas com aerobarco em plantas daninhas aquáticas no lago da Hidrelétrica de Jupiá

Os objetivos deste trabalho foram quantificar as exposições dérmicas (EDs) e respiratórias (ERs) proporcionadas ao piloto e ao seu ajudante nas aplicações de herbicidas para o controle de plantas daninhas aquáticas com aerobarco; classificar essas condições de trabalho em seguras ou inseguras; e calcular a necessidade de controle das exposições (NCE) e o tempo de trabalho seguro (TTS). O aerobarco utilizado tinha casco de alumínio (4,85 x 2,42 m) e acionamento por hélice acoplada a motor a gasolina de 350 HP. O equipamento de pulverização era composto por bomba de diafragma com fluxo máximo de 49,69 L min-1, pressão máxima de 25 kg cm-2, acionada por motor a gasolina de 4 HP, e tanque de calda de 189 L. A barra de pulverização de alumínio era composta de duas seções laterais de 3 m, posicionadas na linha entre o encosto do banco do piloto e o início da estrutura protetora da hélice. Cada seção da barra tinha seis bicos com pontas de jato plano com indução de ar AI 100 03, espaçados de 0,5 m, e uma ponta OC 20 fixada em cada extremidade. O conjunto de pontas pulverizava faixas de 6 m de largura e aplicava o volume de calda de 200 L ha-1. O sistema tinha gerenciador de fluxo, controlado por central eletrônica acoplada a DGPS (com precisão submétrica), para corrigir automaticamente a vazão em função de alterações na velocidade real da embarcação. As EDs e ERs aos herbicidas foram calculadas com os dados substitutos das exposições às caldas, avaliadas com os traçadores cobre e manganês adicionados às caldas. As exposições foram extrapoladas para uma jornada de trabalho de seis horas. A segurança das condições de trabalho foi determinada com o cálculo da margem de segurança (MS), utilizando-se a fórmula MS = (NOEL x 70)/(QAE x 10), em que QAE = quantidade absorvível da exposição. As condições de trabalho foram classificadas em seguras, se MS>1, ou inseguras, se MS<1. As exposições proporcionadas pelas condições de trabalho foram de 10,65 mL de calda por dia para o piloto e de 16,80 mL por dia para o ajudante, que fica sentado em uma cadeira a 2,0 m à frente do piloto e da barra de pulverização. Classificaram-se como seguras as aplicações dos herbicidas glyphosate (Rodeo, 6 L ha-1), 2,4D (DMA 806 BR, 8 L ha-1) e fluridone (Sonar AQ, 0,4 L ha-1), para o piloto e o seu ajudante. Classificou-se como insegura a aplicação do herbicida diquat (Reward, 4,0 L ha-1) para as duas condições de trabalho, cujas necessidades de controle das exposições calculadas foram de 65% para o piloto e de 78% para o ajudante do piloto.

Multiple criteria optimization applied to high speed catamaran preliminary design

The demand for high-speed craft (mainly catamarans) used as passenger vessel has increased significantly in the recent years. Looking towards the future and trying to respond to the increasing requirement, high-speed crafts international market is passing through deep changes. Different types of high-speed crafts are being used for passenger transport. However, catamarans and monohulls have been the main choice not only for passenger vessel but also as ferryboat. Generally speaking, the efficient hydrodynamic hull shapes, engine improvements, and lighter hull structures using aluminum and composite materials make possible the increase in cruising speed. The high demand for catamarans are due to its proven performance in calm waters, large deck area compared to monohull crafts and higher speed efficiency using less power. Although the advantages aforementioned, the performance of catamaran vessels in wave conditions still needs to be improved. The high-speed crafts (HSC) market is demanding different HSC designs and a wide range of dimensions focusing on lower resistance and power for higher speed. Therefore, the hull resistance optimization is a key element for a high-speed hull success. In addition to that, trade-off high-speed catamaran (HSCat) design has been improved to achieve main characteristics and hull geometry. This paper presents a contribution to HSCat preliminary design phase. The HSCat preliminary design problem is raised and one solution is attained by multiple criteria optimization technique. The mathematical model was developed considering: hull arrangement (area and volume), lightweight material application (aluminum hull), hull resistance evaluation (using a slender body theory), as well as wave interference effect between hulls, calculated with 3D theory application. Goal programming optimization system was applied to solve the HSCat preliminary design. Finally this paper includes an illustrative example showing the mathematical model and the optimization solution. An HSCat passenger inland transport in Amazon area preliminary design was used as case study. The problem is presented, the main constrains analyzed and the optimum solution shown. Trade off graphs was also included to highlight the mathematical model convergence process.

Comportamiento de ánodos de sacrificio en la protección de aluminio NV-5083 en agua de mar, bahía de Valparaíso

The behavior of aluminum and zinc alloys were evaluated and compared as sacrifice anodes in cathodic protection of aluminum NV-5083 hulls in seawater in Valparaiso bay. Samples of the aluminum alloy used to manufacture boat hulls and Al-Zn-In, Al-Zn-Sn, and Zn anodes were made. Electrochemical behavior was evaluated by means of polarization curves and corrosion potential as function of time. In parallel, galvanized pairs (boat hull-sacriice anode), were designed and immersed in the electrolyte for 16 days, determining the weight loss and evolution of the open circuit potential for each material. The results show that the aluminum based anodes provide the NV-5083 aluminum hull cathodic protection in seawater. However, they do not exceed the economical horizon and useful life of zinc anodes, because the aluminum based anodes present higher corrosion for the protection of a similar exposed area of aluminum.

403 アルミ合金製大型艇の超塑性ブロー成形技術の開発 : 基礎試験による検討(OS3-1 成形加工の新技術)(OS3 加工新技術)

A boat with an aluminum hull has same advantages of light weight structure, high performance and recycling. Superplastic forming has high flexibility in designing a configuration and reduce cost due to less of assembly parts. This paper describes a study on superplastic blow forming for 5083 aluminum alloy. In this study, properties of the material was investigated and 1/10 small size model forming test was conducted for application of FEM. The results showed the process agreed well and could be used to optimize the forming process of an aluminum hull.

Development of an aluminum hull panel for high-speed craft

The design of aluminum hull structures for high speed craft must satisfy strength, weight and producibility requirements. Since these requirements often conflict with each other, there are a number of possible designs. One design is the floating frame, where the bottom hull panel has alternating ‘floating’ transverse frames that are welded on top of the longitudinal stiffeners. This paper presents the results of a three part investigation of an aluminum floating frame which includes 1. design of an aluminum hull panel that satisfies classification rules; 2. completion of finite element analysis and full scale validation on a test panel; and 3. optimization of the panel to obtain a minimum weight design. The finite element analysis correlated well with the strains and deflections obtained from the experimental tests. The subsequent optimization analysis showed that by proper selection of the panel components and the selection of available extrusions, the weight of the original panel design could be reduced by approximately 15%.

AN EVALUATION OF ENERGY CONSERVATION APPROA CHES FOR SURFACE SHIPS

ABSTRACTLower Fleet operating costs and independence from foreign fossil fuel resources are the goals of energy conservation efforts for Navy surface ship. This paper describes an evaluation of a wide variety of energy conservation approaches. A standard 20‐knot, 300‐hour Destroyer mission is established so that all of the approaches can be compared on a total fuel required basis. The approaches studied include use of aluminum hull construction; light weight machinery; trail‐shaft or cross‐connect operation for twin screw ships; improved performance propulsors; advanced power plant types, such as COGAS or cruise engines; use of energy storage techniques to improve ship service generator performance; electrical load reductions; improved performance ship service generators; hull drag reductions; crew size reductions; design margin reduction; reduced performance requirement (such as top speed); and habitability standard reductions. The overall results can be effected by reductions in range requirements as well. Mission duration was held constant at 45 days throughout the study.The results of the study indicate that the combination of these various possible improvements may reduce the fuel used to be as low as one‐third of the current levels. Weight reductions are very effective for achieving significant fuel savings.