Surendran Sankunny

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.

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.