Surendran Sankunny

Container ships move at a higher speed compared to other merchant ship types. A fin attached to the ship hull proves to be more efficient in controlling the moving ship. However, such attachments on the naked hull attract additional problems such as slamming, requirement of continuous maintenance, etc. The main objective of this study is to find the influence of fin action at various angles of attack with the incoming flow and recommend the best possible fin position for the least resistance. While experiments were performed for different angles of attacks of the fin with respect to the flow, a reduction in resistance was observed for an Fn range of 0.13–0.26. The fin was fitted at the lowest possible location of the hull surface at the bow part of the ship. Experimental investigation was done using model tests in a towing tank to determine the resistance of a scaled down model and it was compared with computer simulation. The interaction of a bow fin fitted to a container ship with its own generated and encountering waves are discussed in this paper. It was observed that at certain angles of attack of the fins favourable resistance characteristics were observed. Modifications from the expected resistance due to fin effect are paid attention in this study. Various resistance values for different angles of attack of the fin were compared and an angle of attack of 5° is found to be the best.

Impact loads from incoming waves always challenge the strength of structural parts of a ship. Modern high-speed crafts including naval vessels are subjected to impact loads during high speed and sudden manoeuvre. Wave slamming may damage structural parts and cause flooding of compartments due to impact. Hydrodynamic impact load results in structural damage in conventional marine vehicles. Loads during cargo loading, unloading, shipping of green water, impact with icebergs etc. come under low-velocity impact loads. The structural parts of a ship can also be damaged due to the impact of collision with icebergs as in the case of the Titanic accident. Weapon discharge, flight operation, bulk cargo operation and collision with other structures are other examples of impact load acting on marine vehicles. Severe hydrodynamic impact load may cause damage of shell plating, collapse of bow part, damage of hatch covers, collapse of hull girder etc. Such structural parts should possess sufficient impact strength. Composite shells can be used for hull, deck or hatch covers of bulk carriers to reduce the weight of vehicle and to indirectly increase the pay load capacity. In the present work, cost-effective composites are prepared by adding fillers to improve impact strengths and tested to verify the same. The main objective of the study is to develop a cost-effective composite to be used as part of hull, deck and hatch cover of bulk carrier. Feasibility and selection of fillers to improve impact strength are established. Prior to this, different sizes of fillers and the chemical treatment of filler with acid were considered. Calcium carbonate (CaCO3), silicon carbide (SiC) and alumina (Al2O3) are considered with glass epoxy composite for the above analysis. The additional impact strength due to the application of fillers is determined using Izod impact strength tests. Contact force is considered as a scale parameter for the impact response for composite laminates. Contact force is the force against impact load on composite structures. Contact force and deflection history of composite panels are affected by a number of parameters such as fibres angle, laminate geometry, impactor energy, stiffeners, surface area of impactor and loading eccentricity. Effects of all possible parameters are included and their influence on the response is determined using the well-known package based on finite element method (FEM), ABAQUS. The FEM analysis of Khalili et al. (2011 Compos Struct 93:1363-1375) is used for comparison of results of the present numerical analysis. The study leads to many new insights to designers of cost-effective composite structures. © 2013 Taylor & Francis.

Composite materials are increasingly being used as an accepted alternative to traditional structural materials throughout the globe for various engineering applications. Because of their superior properties and flexibility, these materials are beginning to find innumerable applications replacing existing materials, especially in high-performance engineering domains. The electrospinning process adds a further dimension to enhance the properties of the composite material family by incorporating fibers at their microscale to even sub-nanoscale, enabling the development of advanced composites with enhanced properties. Over the past decades, much research work has understandably been done on these exciting materials. This paper aims to comprehensively map some of the trends in electrospun nanofiber interleaved laminated composite development, marking the milestones achieved and challenges faced. A brief review of the potential applications for these materials will also be put forward in the research outlook for these advanced nanoengineered composites.

This review paper initially summarizes the latest developments in impact testing on polymer matrix composites collating the various analytical, numerical, and experimental studies performed since the year 2000. Subsequently, the scientific literature investigating nanofiller reinforced polymer composite matrices as well as self-healing polymer matrix composites by incorporating core-shell nanofibers is reviewed in-depth to provide a perspective on some novel advances in nanotechnology that have led to composite developments. Through this review, researchers can gain a representative idea of the state of the art in nanotechnology for polymer matrix composite engineering, providing a platform for further study of this increasingly industrially significant material, and to address the challenges in developing the next generation of advanced, high-performance materials.

Container ships are prone to move at a greater speed compared to other merchant ships. The slenderness of the hull of container vessel is for better speed, but it leads to unfavorable motions. The pitch and roll are related and sometimes the vessel might be forced to parametric roll condition which is very dangerous. A fin attached to the ship hull proves to be more efficient in controlling the pitch. The fin is fitted at a lowest possible location of the hull surface and it is at the bow part of the ship. Simulations are done using proven software package ANSYS AQWA and the results are compared. Simulations are done for both regular and irregular seas and the effect of fin on ship motion is studied. P-M spectrum is considered for various sea states.

Friction Stir Welding (FSW) is a relatively new solid state joining technique which is used not only for joining the aluminum and its alloys but also has potential for joining dissimilar materials with very different physical and mechanical properties which are hard to weld using conventional fusion welding processes. Tensile shear testing is used to determine the Mechanical strength of friction stir lap (FSL) welds under static loading, fracture strength (σLap) corresponding to the maximum load in a test over the sample width is widely used as the strength value. During friction stir lap welding (FSLW) of dissimilar metals with large differences in melting temperatures, a metallurgical bond is established through the formation of interfacial intermetallic compounds. However, as these intermetallic compounds are generally believed to be brittle with little ductility, they are generally considered to have detrimental effect on fracture strength. The aim of the present research is to study how the interface structure is affected by FSW parameters and how the formation of interface structure affects fracture of Al-Steel and Al-Ti FSL welds.

The mass of water in the moonpool of a drill ship will be in linear, angular, and coupled motions influencing the moving ship. The water mass in the moonpool is subjected to sloshing and piston modes. These modes of movement of water mass sometimes lead to a larger quantity of green water on the weather deck causing downtime of the vessel in critical conditions. This paper discusses experimental and numerical study on moonpool with different cut-out angles facing the head on side of incoming waves. The study also aims at minimizing the water motion inside the moonpool under the response to the incident waves. It is concluded that the moonpool with cut-out angle configuration reduces the free surface elevation inside it in a considerable level. With the presence of moonpool on board ship, it is inferred that there is modification in damping, inertial and restoring components of loads and moments.

Aluminium alloys provide many benefits and challenges for use in marine environment. Attention on lightweight hulls leads to power saving, better handling and easy transportation. The stiffness and mass of the structure or member is responsible for its natural vibration. The hull panels and stiffeners vibrate at different frequencies when their stiffness is reduced by formation of a crack or any structural problems. If there is a monitoring system on board and by using a sensor detecting the modified vibrations, the maintenance crew senses the spot where urgent repair is needed. Application of composite laminates is convenient in view of portability and simplicity in procedure such as hand lay-up. In this study, the edge-cracked aluminium plates were repaired with one-sided composite patches and their temperature were varied to both low and high temperature levels. Dynamic fracture toughness was determined using Charpy impact test. Three different types of materials were used for composite patching: GFRP (glass-fibre-reinforced plastic), CFRP (carbon-fibre-reinforced plastic) and Kevlar. For each temperature level, two lay-ups were used, viz. three layered and five layered. Aluminium specimens with edge cracks of two different lengths, keeping the width of the crack constant, were prepared. Impact tests were performed for the prepared specimens at different temperatures. The fracture toughness of aluminium strips reinforced with patches was determined and compared with the energy absorbed during the impact of the corresponding specimen without the patch. It was observed that the specimen with patches gave a higher fracture toughness value when compared with that without the patch; corresponding observation on aluminium has been made along with patch at these temperatures. The patch using Kevlar was found to be the best among the three composites. Followed by these experiments, simulations using FRANC 2D software were carried out for finding stress intensity factor at different crack lengths with and without patches. The research has a spin-off application in the selection of materials used for patching and hence in the maintenance of LPG (liquefied petroleum gas) and LNG (liquefied natural gas) storage tanks under cryogenic conditions. © 2013 Copyright Taylor and Francis Group, LLC.

Light-weight metals like aluminium are preferred to for building of high speed crafts, naval ships, superstructures of commercial ships and offshore platforms. In plate joining, the efficiency of joint is a measure of its impact resistance and structural-integrity. The plates welded together should function effectively against any external loads under emergencies. An ideal welded joint should possess superior weld strength with good impact resistance. Cold metal transfer (CMT) is a proven type of welding technique which is proposed for marine fabrications. Plates of aluminium alloys with grade AA5086-H111 and AA6061-T6 are welded together using a filler, AA4043. For the purpose of plate joining, parameters like current, voltage, arc length, shield gas pressure, etc. are varied to arrive at a continuous weld without any crack. In this study, welded thin plates are subjected to tensile test and thereafter impact loads are applied. The plates are subjected to impact loads in the range of sub-ordinance level velocities, feasibility of ordinance and ultra-ordinance can be scaled and compared. Thus, various ballistic loads are applied at the welded joints. Response and terminal ballistics limit are determined for thin plates of thickness 1.2 and 3 mm plates. This study consists of simulation in Abaqus software and experiments using a gun prepared in the laboratory. It was observed that, there was petaling in very thin plates and perforations by plugging for lower ballistic loads and thinner plates. The work gives new insights in the application of CMT in joining of plates of different metals with varied thickness values. The experimental results can be used as bench marks to compare results of simulations for thin plates. While experiments were done for thin plates, only computer simulation was done for thicker plate of 12 mm which is usually accepted for fabrication in industry.

It is well known that during the operating condition of any metallic structural system the dynamic crack growth speed is in the order of 1-2 km/s. Industrial finishes like coating which form the integral part of manufacturing is adopted to improve fracture toughness of metals. These coated samples coated with thin films are mechanically tested by Charpy V-notch impact tester for estimating dynamic fracture toughness. Coatings improve the wear and corrosion resistance of materials; they tend to reduce the strength of materials, because of the increased residual stresses due to the coating process. Defects cannot be precluded from these coated and treated components; strength of those components in the presence of these defects can be analyzed by fracture mechanics approach. An attempt has been made to analyze the effectiveness of coating methods like electroplating, PVD (Physical Vapour Deposition), coating thickness and the service temperature on the fracture behaviour of metals. Experiments have been carried out on EN8 steel and aluminium for different temperatures and the later samples were corroded for 2400 h and tested for corrosion resistance. The specimen preparation and experimentations were carried out according to the ASTM standard E-23. Finite element analysis was done by FRANC 2D (Fracture Analysis Code) for estimating the stress intensity factor at different crack lengths along with influence of temperature and corrosion. PVD coated samples of Al-N (aluminium nitride) and nano-crystalline layer of Ti-Al-N (titanium aluminium nitride) showed improved dynamic fracture toughness properties. The same set of samples showed decrease in stress intensity factors and excellent corrosion resistance compared to conventional Ni (nickel) and Cr (chromium) coated samples. Mechanical behaviour of selected metals under heat affected zone is of also discussed in this paper, the study aims at both coated and uncoated cases. Performances of metals in cryogenic condition are also paid attention in this paper. © 2013 Elsevier Ltd.