Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Forward and reverse modelling of flow forming of solution annealed H30 aluminium tubes

Abstract: Modelling of flow forming of tube-shaped solution annealed H30 Aluminium alloy is considered in the present study. Initially, a total of 136 experiments have been conducted to realize the process and subsequently influences of three inputs (feed–speed ratio, roller infeed and axial stagger) on the three outputs, viz. internal diameter, springback and ovality have been studied. Three neural network-based approaches (back-propagation neural network, limited-memory BFGS network and genetic neural system) have been developed for forward as well as reverse modelling of the process. During forward modelling, the performances of the three neural network-based approaches have been compared with the regression model. It is seen that GANN has performed much better compared to the other methods. Percentage accuracy in predicting ovality using regression analysis is the worst, and it necessitates consideration of more input process parameters for better prediction accuracy. However, NN-based approaches adapted such cases well. Comparison of all the three NN-based approaches among themselves has been made during reverse modelling. During this process, prediction accuracy, using LBFGSNN, is found to be better than the other two methods. Thus, it is perceived that NN-based models might suit better for prediction of shape accuracy of flow-formed shell.

Design and Analysis of Fusion Algorithm for Multi-Frame Super-Resolution Image Reconstruction using Framelet

Abstract: A enhanced fusion algorithm for generating a super resolution image from a sequence of low-resolution images captured from identical scene apparently a video, based on framelet have been designed and analyzed. In this paper an improved analytical method of image registration is used which integrates nearest neighbor method and gradient method. Comparing to Discrete Wavelet Transform (DWT) the Framelet Transform (FrT) have tight frame filter bank that offers symmetry and permits shift in invariance. Therefore using framelet this paper also present a framelet based enhanced fusion for choosing the fused framelet co-efficient that provides detailed edges and good spatial information with adequate de-noising. The proposed algorithm also has high advantage and computationally fast which are most needed for satellite imaging, medical imaging diagnosis, military surveillance, remote sensing etc. Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 292-299, DOI: http://dx.doi.org/10.14429/dsj.65.8265

Separation Dynamics of Air-to-Air Missile and Validation with Flight Data

Abstract: Prediction of flight characteristics of a store in the vicinity of an aircraft is vitally important for ensuring the safety of the aircraft and effectiveness of the store to meet the mission objective. Separation dynamics of an agile air-to-air-Missile from a fighter aircraft is numerically simulated using an integrated store separation dynamics suite. Chimera cloud of points along with a grid-free Euler solver is used to obtain aerodynamic force on the missile and the force is integrated using a rigid body dynamics code to obtain the missile position. In the present work, the suite is applied to a flight test case and sensitivity of trajectory variables on launch parameters is studied. Further, the results of the suite are compared with the flight data. The predicted body rates and Euler angles of missile compare well with the flight data.

A nonlocal continuum mechanics model to estimate the material property of single-walled carbon nanotubes

Abstract: A subject of current technological interest is that of nanotechnology. It would appear that nonlocal continuum mechanics could potentially play a useful role in analysis related to nanotechnology applications. The present work explores this potential in the context of a specific application. The length scales associated with nanotechnology are often sufficiently small to call the applicability of classical continuum models into question. Atomic and molecular models, while certainly conceptually valid for small length scales, are difficult to formulate accurately and are almost always computationally intensive. Nonlocal continuum models represent attempts to extend the continuum approach to smaller length scales while retaining most of its many advantages. Therefore, continuum models need to be extended to consider the scale effect in nanomaterial studies. This can be accomplished through proposing nonlocal continuum mechanics models, where the internal size scale could be simply considered in constitutive equations as a material parameter. Usually, the magnitude of the nonlocal parameter e0, determines the nonlocal effect in the analysis. The modeling and analyses of nanostructures based on flexural displacement, require an accurate estimate of nonlocal scaling parameter. Such an attempt is made in the present work. From the present analysis, the value of the scale coefficient (e0a, a is carbon-carbon bond length) is recommended to be about 0.11 nm for the application of the nonlocal theory in the analysis of carbon nanotubes.