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Padhy S.,Proof and Experimental Establishment | Sanyal S.,Indian Institute of Technology Kharagpur | Meena R.S.,Rajasthan Technical University Kota | Chatterjee R.,Indian Institute of Technology Delhi | Bose A.,Proof and Experimental Establishment
IET Microwaves, Antennas and Propagation | Year: 2014

The preparation and complex permittivity and permeability measurement of a new U-type of hexaferrite microwave absorbing material (Ba4 Mg2-x MnxFe36 O60) is reported for different value of x in range 0 ≤ x ≤ 2. Complex permittivity and permeability values of hexaferrite pellets are measured using a vector network analyser (VNA) in X-band. The reflection loss of the materials is computed for different values of x and thickness using the measured permittivity and permeability values. The optimum reflection loss is found to be -43 dB for hexaferrite pellet (x = 0.5) at a thickness of t = 1.7 mm. Microwave absorbing paint pellets are prepared by mixing hexaferrite powder with polyimide solution and their complex permeability and permittivity are also measured using a VNA. Using these measured values, radar cross-section reduction simulation for artillery shells has been carried out using electromagnetic simulation software in the 8-10 GHz frequency range. A maximum radar cross-section reduction of 15 dB has been observed for a 30 mm artillery shell at 9 GHz. © The Institution of Engineering and Technology 2014.

Panda H.S.,Proof and Experimental Establishment | Ghosh Moulic S.,Indian Institute of Technology Kharagpur
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2011

An analytical solution for buoyancy-induced gas microflow in a tall differentially heated enclosure with isothermal vertical walls is presented. The Navier-Stokes system has been solved. The Boussinesq approximation has been employed. Wall-fluid interactions are modelled by first-order velocity slip and temperature jump conditions. The analysis presented covers continuum to slip-flow regime. A functional form for the Nusselt number has been derived analytically. The results indicate that as the Knudsen number increases, the Nusselt number decreases.

Sahoo S.,Proof and Experimental Establishment | Laha M.K.,Indian Institute of Technology Kharagpur
Defence Science Journal | Year: 2014

In the present study, the drag variation and trajectory elements estimation of a supersonic projectile having two different nose shapes are made numerically. The study aims at finding the coefficient of drag and shock wave pattern for 130 mm artillery shell fitted with recovery plug or with fuze, when travelling at zero angle of attack in a supersonic flow of air. The coefficient of drag (CD) obtained from the simulation is used as an input parameter for estimation of trajectory elements. The numerical results, i.e., the coefficient of drag at different Mach numbers and trajectory elements are validated with the data recorded by tracking radar from an experimental firing. Based on numerical results and data recorded in experimental firing, the coefficient of drag in the case of the shell with recovery plug is 2.7 times more than for the shell with fuze. The shock wave in the case of the shell with recovery plug is detached bow shock wave, whereas in the case of a shell with fuze, the shock is attached. The results indicate that the coefficient of drag increases with detached shock wave and an increase in the radius of the shell nose. Good agreements were observed between numerical results and experimental observations. © 2014, DESIDOC.

Anguswamy V.,Proof and Experimental Establishment | Gangwar R.K.,Proof and Experimental Establishment
Proceedings - 27th International Symposium on Ballistics, BALLISTICS 2013 | Year: 2013

Gun Tube Muzzle brake occasionally forced into unusual and distinct conditions when subjected to powerful release of energy due to shock-on-shock interaction between reflected precursor shock wave and on coming shock wave due to main gas flow. Generation of high pressure shock wave within the Baffle plates causes a very high stress within microsecond durations and conditions attained force Muzzle Brake materials into irreversible states not fully encountered in any other excitation. Roughly three quarter of the available propellant energy passes through the muzzle of the gun. Propellant designers are facing ever-increasing demand for the requirement of high energetic propellant for Howitzer/Field gun. Propellant gas thrust and its deflection at higher gas velocity in gun muzzle brake create problem to its structural and functional effectiveness. Case study of failure Muzzle Brake of a high caliber gun at higher gas velocity is described in this paper. Analysis of past failure of muzzle brake of different caliber guns, and their conclusions validated by Conduct of dynamic test firing, together with study of leakage of propellant gases past the loosely rammed shot would reveal cause of muzzle brake damage and ultimately affecting the safety of weapon system. Theory for cause of Muzzle Brake damage has been proposed which involves shock-on-shock interaction with increasing heat transfer and pressure load of very high order.

Anguswamy V.,Proof and Experimental Establishment | Gangwar R.K.,Proof and Experimental Establishment
Proceedings - 27th International Symposium on Ballistics, BALLISTICS 2013 | Year: 2013

Conventionally Gun propellant ignition process entails three phases. Ignition time lag, flame spreading and chamber filling. The ignition will be successful once enough grain surface is ignited and burning is self-sustaining. So that chamber pressure continues to rise to peak value. The efficiency of burning depends mostly on how the process is initiated by the primer and how early Peak Pressure value is reached. The existing evaluation of Primer is based on its functioning with complete ammunition where in adequate muzzle velocity of the projectile gives measure of efficient functioning of primer. The paper deals with proposed economic evaluation of primer for its functionality and experiments conducted to measure the efficiency of primer in the laboratory by analysis of the slope of Pressure-Time trace using standard propellant, control volume and flow rate of gases during burning.

Padhy S.,Proof and Experimental Establishment | Panigrahi S.,Proof and Experimental Establishment
Defence Science Journal | Year: 2014

This paper deals with development of velocity measurement methodology based on projectile shock wave pressure measurements. The measurement principle is based on the fact that, whenever a projectile moves with supersonic velocity, shock wave fronts are produced along the trajectory of the projectile. Measurement configuration has been developed for measuring the shock wave pressure associated with projectile in flight, and hence, projectile velocity has been calculated. This paper covers various aspects of shock waves, generation of N Waves, feasibility study for capturing shock wave using dynamic microphone. Finally, suitable piezo-electric sensor has been selected and deployed in the trials and shock wave signature has been captured. From shock wave pressure, the projectile velocity has been computed. © 2014, DESIDOC.

Nayak N.,Proof and Experimental Establishment | Banerjee A.,Proof and Experimental Establishment | Sivaraman P.,Naval Materials Research Laboratory
Defence Science Journal | Year: 2013

Ballistic impact response of ceramic- composite armor, consisting of zirconia toughened alumina (ZTA) ceramic front and aramid laminated composite as backing, against 7.62 mm armor piercing (AP) projectiles has been studied. Two types of backing composite laminates i.e. Twaron-epoxy and Twaron-polypropylene (PP) of 10 mm and 15 mm thickness were used with a ceramic face of 4mm thick ZTA. The ceramic- faced and the stand alone composite laminates were subjected to ballistic impact of steel core 7.62 mm AP projectiles with varying impact velocities and their V50 ballistic limit (BL) was determined. A sharp rise in BLwas observed due to addition of ceramic front layer as compared to stand alone ones. The impact energy was absorbed during penetration primarily by fracture of ceramic, deformation and fracture of projectile and elastic-plastic deformation of flexible backing composite layer. The breaking of ceramic tiles were only limited to impact area and did not spread to whole surface and projectile shattering above BLand blunting on impact below BLwas observed. The ceramic- faced composites showed higher BLwith Twaron-PP as backing than Twaron-epoxy laminate of same thickness. This combination of ceramic-composite laminates exhibited better multi-hit resistance capability; ideal for light weight armor. © 2013, DESIDOC.

Nayak N.,Proof and Experimental Establishment | Banerjee A.,Proof and Experimental Establishment | Datta D.,Bengal Engineering and Science University
Defence Science Journal | Year: 2012

Immersion type ultrasonic C-scan has been performed on Twaron-epoxy (T-E) and Twaron-polypropylene (T-PP) composite laminates impacted by 7.62 mm armor piercing (AP) projectile with different striking velocities to assess the bullet inflicted damage area. Square zones of size 72 mm by 72 mm around each impact area are subjected ultrasonic C-scan in pulse echo mode. Ultrasonic features are extracted and processed to estimate the damage area in the laminates due to each impact. The variation in internal damage area is correlated with ballistic properties of composite laminates. It is observed that in the similar range of impact velocity, the damage area is invariably higher in composites made from thermoplastic polypropylene (PP) resin compared to the thermoset epoxy resin. The internal damage area of impacted panel is found to decrease with increase in impact velocity for both the types of resin matrix which corroborated the trend in experimental ballistic curve. The internal damage area, however, increases substantially when shot lodging takes place inside the laminate below ballistic limit or upon excessive yawing. © 2012, DESIDOC.

Ray K.,Proof and Experimental Establishment
Defence Science Journal | Year: 2010

For test and evaluation of a proximity fuze, it is necessary to know the distance offset of the exploding ammunition round, fitted with the fuze, from a specific target. If the event is recorded using in-line high-speed photography the event of explosion can be resolved in time, and it becomes necessary to ascertain the position of the round, wrt the target, as it is exploding. An estimation of intensity centroid position fails as the flash is non-uniform in nature and is partially occluded by the exploding round. This paper is about an approach to find the location of the round using 2-D shapes fitting of the explosion patch. © 2010, DESIDOC.

Ray K.,Proof and Experimental Establishment
Pattern Recognition | Year: 2013

Edge detection is one of the oldest image processing areas that are still active. An important current area of study involves development of unsupervised edge detection algorithms. In this work a paradigm of unsupervised edge detection is proposed that is based on the computational edge detection approach introduced by Canny. It is a simple and computationally cheap technique that achieves non-trivial results. Additionally as a byproduct it generates information about the content and severity of noise in the image. The proposed technique uses a fast edge detector to generate the initial edge mask and subsequently optimizes that by studying the behavior of a proposed details estimator. The study of the same estimator also offers insight about the noise characteristics of the image. © 2013 Elsevier Ltd.

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