Surendran Sankunny

In the past, there were very serious casualties under the actions of extreme waves including loss of precious lives. There are cases like loss of M V Derbyshire (Faulkner, 2001) due to hatch cover failure in extreme weather conditions. Use of composite materials in marine fields as major or minor components off floating platforms is discussed in this paper. Application of composites on board ships reduces the self weight and lowers the position of vertical centre of gravity of the floating vessel. There are advantages in using composite structures in marine environment. A link-span fitted with a composite deck and the feasibilities of using composite for hatch covers of bulk carrier ship is described in this paper. In the case of bulk carriers, failure of hatch cover especially in the forward part of the vessel leads to flooding of the forward cargo compartment and occasionally results in fatal casualty. The foremost hatch cover and the next one within 25% length of the vessel © 2010 by ASME.

Fracture toughness is a material property in the same sense that yield strength is a material property. The determination of fracture toughness for dynamic loading conditions is not very straight-forward, as dynamic crack growth speed in supersonic speed and the speed range is 1 to 2 km/sec. The improvement of fracture toughness of metals plays a vital role in the design and manufacturing of structural components. To achieve this purpose, industries rely up on coatings which are an integral part of manufacturing. These coated samples are tested by Charpy V-notch impact testing for estimating dynamic fracture toughness. These coatings improve the wear and corrosion resistance of the materials and they tend to reduce the strength of the materials, because of the increased residual stresses due to the coating process. These defects cannot be precluded from these coated and treated components. The strength of those components in the presence of such defects can be analyzed by fracture mechanics approach. An attempt has been made to analyze the effect of coating methods like electroplating and PVD (Physical Vapour Deposition), coating thickness, heat treatment and the service temperature on the fracture behaviour of metals. The experiments have been carried out on EN8 steel and aluminium for different temperatures. The specimen preparation and experimentations were carried out according to the ASTM standard E-23. The FRANC 2D (Fracture Analysis Code) has been relied upon for estimating the stress intensity factor at different crack length and temperature. Copyright © 2012 by ASME.

A moonpool is meant to access the underwater part of hull from onboard ship. Moonpools are openings right through the hull from deck to bottom, allowing equipments, ROVs, etc. to be put into the water at a location on the vessel under permissible ship motion condition. Open moonpools in a drillship are causing additional resistance when the ship is in forward speed. It was shown that the water inside the moonpool started to oscillate at forward speed. The drillship is mainly subjected to two types of motions of water mass inside the column namely, piston mode and sloshing mode. The later mode will be dominant in longer moonpools and piston mode in shorter. The amplitude of water particles inside the moonpool is correlated with the forward speed such that increased forward speed leads to increased amplitudes. The main objective of this study is to find the total resistance and the free surface flow caused by the moonpool when the drillship is at low forward speed condition. Drillship with and without moonpool are considered for the study. Proven packages are used to calculate the calm water resistance of the drillship with moonpool. The incremental change in resistance caused by the moonpool in forward motion is a measure of water motion inside the moonpool for that particular field.

Control devices are selected in the preliminary design stage of any large platforms. This is true for deciding fin area for roll/pitch control of moving platform and thruster sizes and numbers for maneuvering assistance in the case of very low speed conditions. For moored platform the excursions are to be determined to activate the thruster system to reduce the line tension. In the case of a drill ship with moonpool there are some additional parameters of interaction. To some extent the parameters can be contained by optimizing the size and shapes of moon pools on board ships. The dynamics of a moored platform fitted with moon pool are determined here. Such responses are necessary to arrive at the actual sizes and numbers of thrusters to keep the vessel within the tolerances of excursion for ease and accurate operations. © IFAC.

Manufacture of coatings to tackle the biofouling menace has been of prime concern for the shipping industry since industrial revolution. Even though many types of coatings exist in the market, they have not been able to wipe out the problem of biofouling completely. The proposed approach which combines both the resistance due to biofouling on ships, as well as biofouling characterization, will surely serve as a critical input for the manufacture of efficient anti-fouling coatings. Resistance simulations have been carried out for a tanker ship by Maxsurf® wherein the hull fouling effect has been accounted for by modified ITTC 1978 empirical formula considering roughness. Different draft conditions were relied upon to find out the resistance at various Froude numbers. The fouling growth conditions considered are small and medium calcareous fouling. The simulated results also have been validated by towing tank experiments, for no-foul condition, for speeds varying from 0.3 to 1.1 m/s and different drafts. The additional power requirement was determined for various loading conditions and speed ranges.

Use of Steel and Aluminium is very well accepted in marine industry. For metallic structures coatings are to be given to prevent corrosion due to salty atmosphere existing in tropical countries. Ship building industry has been concentrating on the application of composite materials as part of ship hulls to build high speed crafts and naval ships. Most of such vessels are made of composite laminates strengthened by stiffeners of various sectional and mechanical properties. The structural parts vulnerable to higher loads in sea operations are paid attention in this paper. In marine field uses of composite materials are increased drastically due to their superior properties such as ratio of strength to weight, improved corrosion, environmental resistance and life cycle cost. It is susceptible to damages under impact load. These damages cause considerable reduction in strength and stiffness. Therefore, the impact response of fiber reinforced laminated composites are to be analyzed. Usually ships are subjected to loads from wave breaking, bottom slamming, bow slamming and stern slamming. In the past there were accidents due to collapse of hatch cover because of wave breaking. In impact loads there are two types namely low velocity impact and high velocity impact. In marine context low velocity impact is more relevant. The deterioration of steel in saltwater is well known since decades. There are advantages if composites are used for ships as structural parts. The designer has to develop alternate composition of composite panel using chemicals addition. He/she should measure the impact strength of the above mentioned panel prepared using chemical additives. It is highly desirable to have a record of the composition of composite panel for most favourable operating conditions.The methodology covers, experimental technique to find impact strength, finite element analysis using the FEM packages ANSYS for static analysis and ABAQUS for impact load analysis. © 2013 Taylor & Francis Group.

Cold Metal Transfer (CMT) is a proven type of welding method using Metal Inert Gas (MIG). It is a welding technique which can be employed for marine fabrications too. Plates of AA5086-H111 and AA6061-T6 with AA4043 filler is welded by CMT. Parameters like current, voltage, arc length, shield gas pressure etc. are varied to obtain a continuous weld without any crack. Welded thin plates are subjected to a tensile test as per American Welding Society (AWS B4.0:2007) and thereafter impact loads are applied. The plates subjected to impact loads in the range of sub-ordinance level velocities, the feasibility of ordinance and ultra-ordinance can be scaled and compared. Responses and terminal ballistics limit are determined for plate thickness of 1.2 mm and 3 mm. Present work consists of simulation using Abaqus Software and experiments using Laboratory prepared gun. It was observed that, there was petaling in very thin plates and in some plates it was perforated by plugging for lower ballistic loads and thinner plates. The work gives new insights into the application of CMT in joining plates of different materials with varied thickness values. The material property of plates joined by this welding method was found to be new resource information to the permanent literature of material technology.