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R S.,DRDL | Ismail S.,DRDL | P. C. J.,DRDL | P. S. R. A.,DRDL
Structural and Multidisciplinary Optimization | Year: 2017

Shallow domes subjected to external pressure are extensively used in missile structures. The critical failure mode for these domes is buckling due to external pressure. Different closed form solutions are available to evaluate buckling pressure of dome shapes like ellipsoid and torisphere. The torisiphere dome is the optimum dome shape among conventional domes. Shape optimization is carried out to find the optimal dome shape among shallow domes subjected to external pressure. Dome geometry is generalized by cubic bezier polynomials. For carrying out shape optimization, a low fidelity model is preferred which can predict the critical buckling pressure of a general dome shape. Towards this a unified model is proposed which meets the above requirement. Using this unified model, shape optimization of dome for minimization of mass is carried out subjected to buckling constraint. The study yielded a dome shape different from conventional dome shapes with a mass saving of 6% over torispherical dome while meeting the buckling constraint. The results of unified model are also validated with high fidelity Finite Element Analysis. © 2017 Springer-Verlag GmbH Germany

Sarkar A.K.,DRDL | Padhi R.,Indian Institute of Science
Proceedings of the IEEE International Conference on Control Applications | Year: 2013

Three-dimensional impact angle constrained air-to-air missile guidance problem with third order autopilot in loop is investigated using model predictive static programming (MPSP). MPSP is inspired from the model predictive control and approximate dynamic programming philosophies. It inherently minimizes control (lateral acceleration) demand throughout the trajectory in addition to meeting the terminal hard constraint. Two different formulations are explored in this study. In one case MPSP is kept blind about existence of autopilot, where as in other case autopilot dynamics is incorporated explicitly in MPSP problem formulation. Terminal impact angle constraint along with required miss distance are posed as hard terminal constraint in the problem definition itself. It is observed from the extensive simulation studies that the proposed scheme performs better as compared to the classical proportional navigation guidance for intercepting moving and maneuvering targets in the air. © 2013 IEEE.

Chakrabarti A.K.,DRDL
2010 2nd International Conference on Reliability, Safety and Hazard, ICRESH-2010: Risk-Based Technology and Physics-of-Failure Methods | Year: 2010

To produce an item defect-free has been a challenge in engineering industry. Well-established statistical methods are available to estimate the reliability of the product, but such methods are mostly applicable when a large data base is available. Attempts have been made through various logical means to design and produce a component with high reliability. Identifying the critical parameters and essentially their inter-connectivity are major issues to ensure reliability. A concept christened as Bird's Nest is evolved to bring out all issues of design, manufacturing, marketing etc. in a single frame. Availability of such information in the beginning of a development process helps in a big way to achieve defect free and safe system. © 2010 IEEE.

Jain P.C.,DRDL | Mukherjee A.,Thapar University | Krishna Y.,DRDL
Aerospace Science and Technology | Year: 2011

In this study, response of a flight vehicle component to rocket noise is considered. Tuned mass dampers, hitherto used in low frequency excitation, have been utilized to attenuate high frequency, broad band excitations. Modally tuned dampers have been investigated for a variety of input excitations. Modal dampers exhibit significant attenuation of all input signals. © 2010 Elsevier Masson SAS.

Sanjay Anandrao K.,Advanced Systems Laboratory | Gupta R.K.,Advanced Systems Laboratory | Ramchandran P.,DRDL
Structural Engineering and Mechanics | Year: 2012

Large amplitude free vibration and thermal post-buckling of shear flexible Functionally Graded Material (FGM) beams is studied using finite element formulation based on first order Timoshenko beam theory. Classical boundary conditions are considered. The ends are assumed to be axially immovable. The von-Karman type strain-displacement relations are used to account for geometric non-linearity. For all the boundary conditions considered, hardening type of non-linearity is observed. For large amplitude vibration of FGM beams, a comprehensive study has been carried out with various lengths to height ratios, maximum lateral amplitude to radius of gyration ratios, volume fraction exponents and boundary conditions. It is observed that, for FGM beams, the non-linear frequencies are dependent on the sign of the vibration amplitudes. For thermal post-buckling of FGM beams, the effect of shear flexibility on the structural response is discussed in detail for different volume fraction exponents, length to height ratios and boundary conditions. The effect of shear flexibility is observed to be predominant for clamped beam as compared to simply supported beam.

Choudhary M.K.,DRDL | Naresh Kumar G.,DRDL
IFAC-PapersOnLine | Year: 2016

This paper presents an ESO based Control design for ball and beam system which is one of the most sought after problem for control engineering students. The system comprises a long beam which is moved by using servo motor and a ball on which it rolls with respect to Beam motion. In this design, estimation of a virtual state ("disturbance") is carried out online with state observer and these states are used in controller to nullify the effects of actual disturbances and uncertainties in the plant. While designing controller, simpler model is used, thus avoiding accurate modeling of the system. Any nonlinear term and unknown parameter in the plant can be considered as internal or external disturbance. This is the peculiar feature of automatic disturbance rejection control or ESO based control scheme. Hence, linearized model of ball and Beam is considered. All simulations have been carried out with the help of MATLAB and SIMULINK. Using this algorithm, controller shows very good disturbance rejection capability and it has been shown with simulation results. © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

Sirisha Ch.V.,DRDL | Das R.,DRDL
IFAC-PapersOnLine | Year: 2016

In general, anti tank weapons are designed to attack the tank on the top of the tank, where the armour is relatively weak compared to the front and sides of the tank. In this paper, a generalized guidance philosophy for top attack mode is described. This paper presents a novel guidance philosophy which enhances the impact angle for top attack mode by using seeker measurements. This proposed method also reduces the weight and cost of the weapon system by eliminating the need for Laser Range Finder, which is primarily used for target range measurement. Sensitivity analysis of the algorithm is carried out with different parameter perturbations. Lastly, the performance of the algorithm is evaluated through nonlinear Six Degrees of Freedom simulation in time domain. © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

Vijayakumar G.,DRDL | Kachroo A.K.,DRDL
Applied Mechanics and Materials | Year: 2014

Missiles fly at supersonic and hypersonic speeds. Airframe forms the aerodynamic shape of the missile and houses several components essential for mission with suitable structural supports. The missile airframe is subjected to high rate of heating caused by kinetic heating due to very high vehicle speed. Heat transfer analysis of the missile airframe structure is required to be performed for wall temperature predictions to select the material of missile construction with suitable wall thickness and also to check design adequacy for ensuring the safe operation in the severe thermal environment experienced during flight. This paper describes the methodology of evaluation of heat flux distribution over missile wall, prediction of missile wall temperature distribution considering airframe as heat sink and validation of the methodology against flight data. Heat flux has been estimated using classical engineering methods for both stagnation as well as off-stagnation regions including the effects of angle of attack, rarified flow, thermal radiation and solar heating. Transient three dimensional heat transfer analysis with convective and radiative boundary conditions has been carried out for predicting the missile wall temperature profiles. Parametric study has been carried out, considering various parameters such as material of construction, thickness and time duration. The prediction methodology has been validated and a close match is observed between the predictions and flight data. © (2014) Trans Tech Publications, Switzerland.

Vijayakumar G.,DRDL | Kachroo A.K.,DRDL
Applied Mechanics and Materials | Year: 2014

Missile airframe experiences large variations in wall temperature along the circumference due to high angle of attack, especially at hypersonic speeds, which leads to large thermal stresses and bending loads. Such a situation with large wall temperature variations occurs due to high angle of attack during flight. Thermal design of the airframe involves the estimation of local flow parameters and heat flux distribution. Kinetic heating analysis has been carried out for the prediction of heat load distribution on missile airframe considering hypersonic flow with high angle of attack for a particular flight trajectory. Out of a set of possible flight trajectories, a trajectory producing minimum circumferential variation in wall temperature, as concluded through kinetic heating analysis, is finalized. Transient three dimensional heat transfer analysis of the airframe is carried out for prediction of wall temperature distribution for proper selection of material of construction of airframe so that it retains its strength at elevated temperatures. Parametric study has been carried out considering various combinations of airframe wall thickness in presence of external thermal protection coating and internal insulation for the finalized trajectory. Based on the present analysis, airframe configuration having axially variable wall thickness corresponding to the selected flight trajectory is finalized. The validation of the methodology adopted for the analysis has been carried out with respect to airframe temperature data acquired during a flight trial of the missile. © (2014) Trans Tech Publications, Switzerland.

Bhattacharjee P.,DRDL | Ramesh Kumar K.,DRDL | Janardhan Reddy T.A.,Osmania University
International Journal of Reliability, Quality and Safety Engineering | Year: 2010

Optimization of any aerospace product results in increasing payload capacity of space vehicles. Essentially weight, volume and cost are the main constraints. Design optimization studies for aerospace system are increasingly gaining importance. The problem of optimum design under uncertainty has been formulated as reliability-based design optimization. The reliability based optimization, which includes robustness requirements leads to multi-objective optimization under uncertainty. In this paper Reliability, based design optimization study is carried out under linear constraint optimization to minimize the weight of a nitrogen gas bottle with specified target reliability. Response surface method considering full factorial experiment is used to establish multiple regression equation for induced hoop stress and maximum strain. Necessary data pertaining to design, manufacturing and operating conditions are collected systematically for variability study. Structural reliability is evaluated using Advanced First-Order Second-Moment Method (AFOSM). Finally, optimization formulation established and it has been discussed in this paper. © 2010 World Scientific Publishing Company.

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