Defense Research and Development Laboratory

Hyderabad, India

Defense Research and Development Laboratory

Hyderabad, India
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Chowdhury R.,National Institute of Technology Warangal | Reddy M.S.,National Institute of Technology Warangal | Jain P. C.,Defense Research and Development Laboratory | Babu P.B.,National Institute of Technology Warangal
ARPN Journal of Engineering and Applied Sciences | Year: 2016

In this study, investigation is carried out to determine the effects on the stress concentration around a cut-out due to reinforcement around the cut-out in a flat plate and a cylindrical shell, subjected to axial and bending loads. The study is further extended, to a flat plate and a cylindrical shell, subjected to compressive load, containing two identical cut-outs along the length to determine the effect on the stress concentration factor, with the variation of the distance between the cut-outs. This study assumes the use of homogeneous, isotropic material. The investigation is carried out using the FEA software package, ANSYS APDL Mechanical. Parametric study is carried out to understand the variation of the stress concentration. Mathematical relations are also established that relate the diameter of the cut-outs to the distance between them at which they cease to influence one another, in a non-dimensional format. © 2006-2016 Asian Research Publishing Network (ARPN).

Anandrao K.S.,Advanced Systems Laboratory | Gupta R.K.,Advanced Systems Laboratory | Ramchandran P.,Defense Research and Development Laboratory | Rao G.V.,Sreenidhi Institute of Science and Technology
Structural Engineering and Mechanics | Year: 2010

Two or more distinct materials are combined into a single functionally graded material (FGM) where the microstructural composition and properties change gradually. Thermal post-buckling behavior of uniform slender FGM beams is investigated independently using the classical Rayleigh-Ritz (RR) formulation and the versatile Finite Element Analysis (FEA) formulation developed in this paper. The von-Karman strain-displacement relations are used to account for moderately large deflections of FGM beams. Bending-extension coupling arising due to heterogeneity of material through the thickness is included. Simply supported and clamped beams with axially immovable ends are considered in the present study. Post-buckling load versus deflection curves and buckled mode shapes obtained from both the RR and FEA formulations for different volume fraction exponents show an excellent agreement with the available literature results for simply supported ends. Response of the FGM beam with clamped ends is studied for the first time and the results from both the RR and FEA formulations show a very good agreement. Though the response of the FGM beam could have been studied more accurately by FEA formulation alone, the authors aim to apply the RR formulation is to find an approximate closed form post-buckling solutions for the FGM beams. Further, the use of the RR formulation clearly demonstrates the effect of bending-extension coupling on the post-buckling response of the FGM beams.

Das C.R.,Indira Gandhi Center for Atomic Research | Albert S.K.,Indira Gandhi Center for Atomic Research | Sam S.,Indian Institute for Plasma Research | Mastanaiah P.,Defense Research and Development Laboratory | And 5 more authors.
Fusion Engineering and Design | Year: 2014

Microstructure and mechanical properties of the weldments prepared from 9Cr-1W reduced activation ferritic martensitic (RAFM) steel using electron beam welding (EBW) process were studied. Microstructure consists of tempered lath martensite where precipitates decorating the boundaries in post weld heat treated (PWHT) condition. Lath and precipitate sizes were found to be finer in the weld metal than in base metal. Accordingly, hardness of the weld metal was found to be higher than the base metal. Tensile strength of the cross weldment specimen was 684 MPa, which was comparable with the base metal tensile strength of 670 MPa. On the other hand, DBTT of 9Cr-1W weld metal in as-welded condition is similar to that reported for TIG weld metal in PWHT condition. © 2014 Elsevier B.V. All rights reserved.

Misra N.,Banaras Hindu University | Kapusetti G.,Banaras Hindu University | Pattanayak D.K.,Banaras Hindu University | Kumar A.,Defense Research and Development Laboratory
Indian Journal of Physics | Year: 2011

Increased use of composites in aerospace and defense application induces the search for heat resistant material. In present study silica reinforced epoxy functionally graded material using quartz fabric is prepared with different thickness. The gradation in silica: epoxy matrix is maintained with one side pure epoxy to opposite side pure silica. Thermal and mechanical behaviour of the composites were studied. It was found that the temperature gradient of 350°C to 950°C could be maintained for 2 to 5 min if the thickness of insulating silica layer is increased from 0.5 mm to 16 mm. Mechanical properties such as flexural modulus and strength of FGM composites were also evaluated. Strength and modulus decreased with increase of insulating layer. © 2011 IACS.

Chandrakanth V.,Defense Research and Development Laboratory | Devendranath Ch.,Defense Research and Development Laboratory | Shamnar A.,Defense Research and Development Laboratory
International Conference on Signal Processing, Image Processing and Pattern Recognition 2013, ICSIPR 2013 | Year: 2013

Sliding DFT analysis is done to calculate the spectrum of the input signal on sample by sample basis. It is very effective technique available to identify the random and abrupt faults in the input data. Spikes constrained in time domain data are spread out in frequency domain corrupting the frequency data and in some cases masking the weak signal in adjacent frequency bins. Using sliding DFT we can isolate the spike from input data or recognize the occurrence and take necessary processing precautions preventing the corrupted data to be passed on for further processing. The sudden discontinuity is identified by sudden increase in side lobe levels of the Doppler filter bank. The effect of the disturbance persists for data length of '2N -1'. But by setting appropriate thresholds it can be identified and can be isolated. In this paper we present hardware architecture to perform the sliding window DFT on FPGA. The architecture is difficult to implement using vendor supplied IP cores as they are designed to work for block input and not by sample by sample data flow. In block data flow it can be identified but cannot be resolved precisely. And since there is no provision to access the twiddle factors in IP cores which form the crux of FFT processing, SDFT realized using IP cores cannot be further optimized thus reducing its configurability. To achieve sliding DFT we have designed customized and configurable DFT block and structured the data flow using memory arrays to realize sliding window operation. © 2013 IEEE.

Mukunda H.S.,Indian Institute of Science | Paul P.J.,Indian Institute of Science | Javed A.,Defense Research and Development Laboratory | Chakraborty D.,Defense Research and Development Laboratory
Acta Astronautica | Year: 2014

This paper aims at extending the universal erosive burning law developed by two of the present authors from axi-symmetric internally burning grains to partly symmetric burning grains. This extension revolves around three dimensional flow calculations inside highly loaded grain geometry and benefiting from an observation that the flow gradients normal to the surface in such geometries have a smooth behavior along the perimeter of the grain. These are used to help identify the diameter that gives the same perimeter the characteristic dimension rather than a mean hydraulic diameter chosen earlier. The predictions of highly loaded grains from the newly chosen dimension in the erosive burning law show better comparison with measured pressure-time curves while those with mean hydraulic diameter definitely over-predict the pressures. © 2013 IAA.

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