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Evaluating Impact Resistance of Aluminum 6061-T651 Plate using Smoothed Particle Hydrodynamics Method
Get PDFPerforming various experimental, theoretical, and numerical investigations for better understanding of behavioural characteristics of metals under impact loading is of primary importance. In this paper, application of smoothed particle hydrodynamics (SPH) method in impact mechanics is discussed and effective parameters on impact strength of an aluminum plate are investigated. To evaluate the accuracy of smoothed particle hydrodynamics method for simulating impact, Recht and Ipson model is first provided thoroughly for both Rosenberg analytical model and smoothed particle hydrodynamics method, and then plots of initial velocity-residual velocity and initial velocity-absorbed energy for target of aluminum 6061-T651 are presented. The derived information and simulation results expresses that the maximum error percentage of smoothed particle hydrodynamics method in compared with Rosenberg analytical model is within an acceptable range. Therefore, the results of smoothed particle hydrodynamics method verify the Rosenberg analytical model with high accuracy. Results reveal that higher initial impact velocity decreases the time of projectile penetration, and so penetration depth and length as well as the local damage rate of plate increases
Comparison of Predicted and Experimental Behaviour of RC Slabs Subjected to Blast using SDOF Analysis
Get PDFExplosions emanating from terrorist attacks or military weapons cause damage to civilian and military facilities. Understanding the mechanical behaviour of reinforced concrete structures subjected to blast is of paramount importance for minimizing the possible blast damage. A full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa, measuring 1.0 m × 1.0 m × 0.08 m, and subjected to 2.7 kg of non-confined plastic bonded explosive, was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force). This paper compares experimentally measured peak displacement values with theoretical values. Theoretical analysis was carried out using single degree of freedom (SDOF) models. The comparison showed that SDOF analysis worked very well in predicting the reinforced concrete slab peak displacement against blast effects. Qualitative analysis after the experiments showed that the blast wave shape generated by the cylindrical explosive was not uniformly distributed on the slabs for the standoff distance of 0.927 m∕kg1/3
Influence of Tool Tilt Angle on Material Flow and Defect Generation in Friction Stir Welding of AA2219
Get PDFHeat treatable aluminium alloy AA2219 is widely used for aerospace applications, welded through gas tungsten and gas metal arc welding processes. Welds of AA2219 fabricated using a fusion welding process suffers from poor joint properties or welding defects due to melting and re-solidification. Friction stir welding (FSW) is a solid-state welding process and hence free from any solidification related defects. However, FSW also results in defects which are not related to solidification but due to improper process parameter selection. One of the important process parameters, i.e., tool tilt angle plays a critical role in material flow during FSW, controlling the size and location of the defects. Effect of tool tilt angle on material flow and defects in FSW is ambiguous. A study is therefore taken to understand the role of tool tilt angle on FSW defects. Variation in temperature, forces, and torque generated during FSW as a result of different tool tilt angles was found to be responsible for material flow in the weld, controlling the weld defects. An intermediate tool tilt angle (1o-2o) gives weld without microscopic defect in 7 mm thick AA2219 for a given set of other process parameters. At this tool tilt angle, x-force, and Z- force is balanced with viscosity and the material flow strain rate sufficient for the material to flow and fill internal voids or surface defects in the weld
Thermal Design, Analysis and Packaging of an Airborne Multi-output Power Supply Unit
Get PDFDesign of airborne multi-output power supply unit (MOPS) is restricted by space, weight and predefined geometry of air flow path. The unit is cooled by ram air and hence, exposed to the extreme external thermal environment that changes typically from +55°C to -40°C, from ground to cruising altitude within a few minutes. Hence the design should meet the thermal requirements of the electronics inside the packaging adequately, for both the positive and negative extremities of the temperature, so that device limiting temperatures are not exceeded. At the same time, it must accommodate the necessary circuitry. Details of the thermal and mechanical design and performance of the MOPS unit at various altitudes, hot spot location, flow requirements and optimal heat sink design are presented in this paper
Effects of Tank Gun Structural Components on the First Shot Hit Probability
Get PDFFire power for a main battle tank is one of the most important performance parameters like survivability and mobility. Fire power effectiveness is directly related to the first shot hit probability, performance of main gun, second armament, gun and turret drive system, fire control system, automatic target tracker, commander and gunner sight etc. First shot hit probability (a measure of cumulative effects of errors) is affected by the variations of the projectile parameters, the main gun structure uncertainties, fire control system errors, interaction between the projectile and the gun barrel and the unpredictable environmental changes. These errors and variations can be eliminated or minimised by understanding and simulating the firing event properly, manufacturing the related parts in high precision, using advanced fire control algorithms, and accurate sensors. In this review study, the effects of main gun structural components on the first shot hit probability are investigated taking into account all of the associated error sources. In order for a main battle tank to have both high and repetitive first shot hit probability under all battlefield conditions the gun structure should respond in a similar manner in successive firings without causing any abrupt change in performance. In this study, first the dynamic behaviour of gun/projectile system is discussed and then the design recommendations for the main gun components such as bearings, gun barrel, recoil system etc. to achieve higher first shot hit probability are reviewed
Evolutionary trends in Transmit/Receive Module for Active Phased Array Radars
Get PDFWorldwide, defense technologies are rapidly evolving and are currently aiming at integrating diverse functionalities like Radar, Electronic Warfare, Communications, etc., on a singular miniaturized platform. Hence, it cannot be denied that the advancements in modern Active Phased Array Radar technologies assume a critical role towards the achievement of this goal. A typical Active Phased Array Radar comprises of an Active Antenna Array Unit (AAAU) consisting of a large number of radiating elements, Transmit/Receive (T/R) Modules with other associated RF and digital circuitry and power electronics. This paper presents mainly the developments in Transmit/Receive (T/R) Module technology, which assimilates various stages of the technological evolution - past, current and futuristic. It discusses how these technologies contribute towards the improvement of efficiency, miniaturization and reliability without compromising its performance parameters
Passive Thermal Management of Launch Vehicle Systems using Phase Changing Materials
Get PDFElectronic systems in expendable launch vehicles and missiles rely on their own thermal inertia to operate for the stipulated time, without overheating, owing to absence of active cooling systems and natural convection at elevated altitude. Traditionally, this inertia is built-into the electronics by increasing its chassis (support structure) mass, proportional to the associated thermal load. For power intensive systems, especially in vehicle upper stages where mass is at premium, this approach results in reduction in payload capability. In the proposed paper, a Heat Sink based on Neopentyl Glycol (NPG) with solid-to-solid phase change (crystalline transformation) is explored as a mass effective alternative due to the material’s capability to absorb a significant amount of energy during phase change. However, due to its lower thermal conductivity, a Thermal Conductivity Enhancer (TCE) to maximize heat transfer had to be employed. The resulting heat sink, utilizing TCE for heat transfer capability and NPG for heat storage capability is called as Hybrid Heat Sink. A heat sink with plate type fins as TCE is realized and a mass reduction factor of 1.4 is achieved against traditional approach. This is followed by a heat sink with pin type fins as TCE where mass reduction factor is increased to 2.6. Effect of thermal cycling and vibration on its performance is also studied
Design for Stuck-at Fault Testability in MCT based Reversible Circuits
No full textTestability leads to a large increment in operating costs from their original circuits which drastically increases the power consumption in logic circuits. This paper presents a new design for testability methodology for the detection of stuck-at faults in multiple controlled Toffoli based reversible circuits. The circuit is modified in such a manner that the applied test vector reaches all the levels without any change in values on the wires of the circuit. An (n+1) dimensional general test set containing only two test vectors is presented, which provide full coverage of single and multiple stuck-at faults in the circuit. The work is further extended to locate the occurrence of stuck-at faults in the circuit. Deterministic approaches are described and the modification methodology is experimented on a set of benchmarks. The present work achieved a reduction up to in operating costs as compared to the existing work implemented on the same platform
Effect of Internal Clearance on Buckling of Multistage Hydraulic Cylinder
Get PDFMultistage cylinders are generally used to lift and tilt heavy loads under controlled speed. In defence applications multistage cylinders are used in missile tilt platform and antenna mast. Earth moving equipment’s such as tippers, dumpers, cranes and compactors uses multistage cylinders for operations. In the present work multistage hydraulic cylinder (telescopic cylinder) with three stage has been analysed using strain energy method and verified with finite element analysis. The research work investigates the effect of internal clearances which reduces the critical buckling load of hydraulic cylinders. The results are validated by buckling load test. The clearances between the tube to piston guides, gland guide to piston rod, clearances due to tube expansion under pressure, initial curvature in the tube, eccentricity of cylinder components and tube ovality are considered in the buckling load test. Describes the comparative study of buckling load tests of three stage hydraulic cylinders having fixed free and hinged mounting with five different internal clearances
Design, Analysis and Characterisation of Spoof Surface Plasmon Polaritons based Wideband Bandpass Filter at Microwave Frequency
Get PDFThis paper presents the wideband bandpass filter (BPF) in the microwave frequency domain. The realisation approach is based on spoof surface plasmon polaritons (SSPPs) phenomenon using plasmonic metamaterial. A novel unit cell is designed for filter design using an LC resonator concept. Then SSPPs BPF is realised using an optimised mode converter and five unit cells. This paper includes a brief design detail of the proposed novel unit cell. The passband of BPF is achieved at approximately 1.20 - 5.80 GHz, 3dB bandwidth is tentatively 4.60 GHz and the insertion loss is less than 2 dB approximately over the passband. The overall dimension of fabricated filter is (90 x 45) mm. A basic schematic of transmission line representation is also proposed to evaluate the BPF structure