Defence Science Journal
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Terrain Accessibility Prediction for a New Multi axle Armoured Wheeled Vehicle
Get PDFBetter terrain accessibility of military vehicle makes it possible to project force at desired points in a theatre of operation. The factors responsible for terrain accessibility are slope, obstacles and soil. Torque requirement for meeting vehicle speed and gradient requirement is understood and can be analytically arrived at. It can be met by appropriate choice of engine and transmission using. There is dearth of information as well as a common metric in quantification of terrain accessibility especially soft soil trafficability. Approach adopted in this study is that of characterisation of vehicle in terms of mobility characteristic and mobility limit parameters and comparing them with vehicle in-service worldwide. Simple empirical relation has been preferred over complex analytical approach for mobility prediction and gradient climbing capability in sand has been predicted and compared with other vehicles. parametric study for tyre sizes vis-a-vis mobility parameters have been obtained and results have been presented for chosen vehicle configuration. Second part of this study is obstacle crossing capability study for standard set of obstacles. Vehicle model has been built in multi-body environment and parameters of significance viz., wheel displacement to verify correctness of model and acceleration at CG for ride comfort and ground reactions for evaluation of dynamic loads on axles have been obtained. Vehicle drivetrain configuration to achieve desired terrain accessibility in terms of soft-soil trafficability and obstacle crossing has been demonstrated
Energy Conservation Method Combining Anti spray Rail and Wedge Flap for High speed Displacement Hulls
Get PDFThe hydrodynamic mechanism and parametric influences of the wedge flap and the anti-spray rail in combination is investigates. A methodology with specific guidelines for incorporating these appendages with significant drag reduction is provided. Small crafts designs frequently require interventional changes to realise the desired guaranteed speed with their installed engine power. The appendages namely, the wedge, flap and anti-spray rails are used as retrofit measures or adapted in new hull forms, in isolation or in combination, to improve the drag and bring down the power requirement. A judicious combination of different appendages can result in significantly reduced drag and therefore power saving. The methodology combines the results of numerical and experimental investigations. The systematic study identifies the parameters for control namely, wedge flap size in terms of the chord length, its orientation vide the angle of the wedge flap, and the anti-spray rail location with respect to the water surface. The choice of the size of the wedge flap is a constrained problem since excessive wedge flap can cause problems related to length and hydrodynamic loading. This study establishes a solution by combination of a minimum integrated wedge flap with properly located anti-spray rail to reduce the drag. The study shows favourable influences due to local pressure and numerical results using a RANSE solver show good comparison with experimental test results. The methodology is a new approach towards drag reduction in new designs as well as drag control by retrofit
Synthesis and Application of Nano structured Bi layer YSZ LZ Thermal Barrier Coating
Get PDFPresent work is on synthesis of high purity Nano-structured TBC materials, Lanthanum Zirconate and YSZ. They were prepared via wet chemical routes, starting from the indigenous source minerals such as zircon and monazite available in the beach sand. This is first time that the results of TBC materials synthesis from these base minerals, their purification and a high end application being presented comprehensively. Their characterisation and thermal barrier application on aeroengine components have been presented. The total oxide impurities being critical to the life of the coating, could be controlled within 0.03 per cent by weight. On comparison with other powders it was found that the indigenously synthesised YSZ powder had practically 100 per cent tetragonal prime phase and no monoclinic phase; whereas others had significant amounts of monoclinic phases present in them. Both YSZ and LZ powders were sinter agglomerated at 850 °C to preclude the possibility of any contamination and sieved. APS process was used to realise nano-structured bi-layer coating on the exhaust nozzle parts of an aeroengine. The components were subjected to rapid thermal transients during long accelerated endurance testing, equivalent to 1000 h of engine operations. The coatings also withstood the gas erosion of supersonic combustion products, vibratory loads of 4 g and more than 30000 nozzle actuations similar to aircraft maneuver. The paper also presents a brief review of implications of a nano-structured thermal barrier coating and certain nuances of chemical synthesis which forms the backbone of the strategies for durable coatings
Towed Acoustic Countermeasures for Defending Acoustic Homing Torpedoes
Get PDFThe growing torpedo threat to ships and submarines demands effective countermeasures for defence. Detection, classification and localisation of an attacking torpedo is the first step towards launching effective countermeasures. Studies are on the rise to use the existing sonar systems to detect torpedoes and subsequently use countermeasures. The use of towed array sonar systems for torpedo detection and acoustic counter measures are the most recent and not reported much in open literature. This paper presents a modular acoustic counter measure approach using towed decoy against acoustic homing torpedoes. Describes the technologies and algorithms required for different modes of towed decoy, which is effective against both active and passive acoustic homing torpedoes. Towed decoy signal generation schemes and their realisation using digital signal processing hardware are outlined in this paper
Numerical Simulation of the TNT Solidification Process
Get PDFThe solidification phenomenon is present in the casting process of energetic materials. In defence industry, trinitrotoluene (TNT) is used as main charge for high explosive ammunitions. The present study tackles the numerical simulation of the solidification process of TNT by means of a two-dimensional transient model in cylindrical coordinates. The heat conduction problem is solved by using the enthalpy method that rewrites the governing equation in terms of this variable. The transient diffusive equation is then numerically solved by applying finite volumes in an explicit scheme. The analysis the mold thickness and the convective boundary conditions are analysed to assess how they affect heat transfer during solidification. Results obtained allow for a better comprehension of this type of problem
Ballistic Behaviour of Austempered Compacted Graphite Iron Perforated Plates
Get PDFIn this study, the performance of austempered compacted graphite iron was evaluated to find its suitability as perforated plates used in add-on armour. Perforated compacted graphite plates were subjected to austenitisation at 900 °C for 2 h followed by austempering at 275 and 400 °C for 1 h. The basic plate was fixed at 400 mm away from the perforated plate and armour and then piercing incendiary projectile was shot from a distance of 100 m. It was observed that both 7 mm and 9 mm perforated plates austempered at lower temperature of 275 °C producing higher hardness and lower ductility were effective in fracturing the penetrating core, thereby significantly decreasing the chances of penetrating the basic plate
Path Planning of Anti ship Missile based on Voronoi Diagram and Binary Tree Algorithm
Get PDFThe path planning of anti-ship missile should be considered both cruising in safety and striking in quick, which is an intractable problem. In particular, it is difficult to consider the safety of each missile path in the path planning of multiple missiles. To solve this problem, the “AREA Algorithm” is presented to divide the relative relations of areas：relative security area of the threat areas and fast-attack area of target approaching. Specifically，it is a way to achieve area division through the relationship between the target and the center of the operational area. The Voronoi diagram topology network, Dijkstra algorithm and binary tree algorithm have been used in the above process as well. Finally, Simulations have verified the feasibility and obvious advantages of “AREA Algorithm” compared with the single algorithm, and the tactical meaning in path planning of multiple missiles
Mixed Layer Budget Terms on Acoustic Propagation A Study based on the Butterfly Track Experiment in the South Eastern Arabian Sea
Get PDFA butterfly type of repeat track cruise was carried out in the South Eastern Arabian Sea (off Minicoy) onboard INS Sagardhwani during July 2016 to Aug 2016. We have also made use of the data from OMNI buoy, AD09, which is about 6 km close to the centre station of butterfly track. Air sea flux, the horizontal current data from AD09 and the time series data collected from the butterfly experiment were analyzed to compute the mixed layer heat and salt budget. The short-term thermo-haline variability off Minicoy, relative contribution of heat/salt budget terms in MLD and its effects on acoustic propagation are addressed in this paper. In this study, we found that most dominating term in the mixed layer heat budget estimation is net surface heat flux followed by the advective terms. However the salinity in the mixed layer is dominated by the contribution of buoyancy mixing due to night time evaporative cooling. During the calm, sunny day, the so-called afternoon effect due to the diurnal heating restricts the sonar range. But during the windy day, the wind/wave mixing prevents the warming of the surface layer which in turn enhances the sonar range. Similarly, the night time cooling also enhance the acoustic propagation range. The presence of Arabian Sea High Salinity Watermass in the surface layer also enhances the acoustic propagation
Modelling of Multi Inductor based Balancing of Battery Pack for Electrical Mobility
Get PDF The pre requisite for success of electrical mobility is driven by development of battery technologies. Reliable performance of electrical mobility necessitates for high energy density battery packs. The advent of Li ion cell chemistry revolutionised the electric and hybrid vehicle advancement due to its high energy density, lighter weight and wide range of temperature performance. Higher operating voltages of the battery are achieved by configuration of the cells in series and parallel combinations. The performance of these battery packs are affected by operating temperature and imperfections in manufacturability which causes mismatches in cell impedance, cell potential and state of charge (SOC) imbalance. These performance issues are overcome by cell and battery balancing techniques. In this paper, a dynamic battery pack balancing circuit by using multi inductor with SOC based logic controller for both cell and battery balancing are presented. The battery pack balancing performances during static, charging, discharging conditions are analysed
