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.

Influence of silicon content on the volume deficit characteristic of cast Al-Si alloys

Abstract: Aluminum alloy castings find extensive applications in automobile and other engineering industries. Production of defect-free castings requires a good understanding of the volume deficit characteristic. The volume deficit of a casting depends on the casting material and casting conditions. Patterson and Engler have classified the volume deficit into four types namely, macrocavities, internal porosity, surface sinking, and volumetric contraction. The influence of process parameters on the characteristics determines the casting quality. The process parameters considered in this study are bottom chill, casting shape, and pouring temperature. Two basic shapes rectangle and cylinder are considered. The volume deficit decreases with an increase in the silicon content. The AA 356.0 alloy shows more amount of volume deficit than AA 413.0 alloy. X-ray computer tomography (XCT) helps to reveal the size, shape, and location of defects in castings. Quantification of internal closed porosity of AA 413.0 casting is done using XCT and successfully validated through destructive testing of castings.

Computational Aerodynamic Study of Body-Intake Configurations

Abstract: Aerodynamic study over body-intake configurations has been carried out using a CFD code, PARAS. Body -Twin Intake and Body-Cruciform Intake configurations were studied. The air- intakes are two-dimensional. Computations were carried out for Mach numbers 2.0 and 3.0, angle of incidence from -10 o to +10 o and roll angles 0 o and 45 o . Computations with and without flow through the intakes were carried out. The CFD results were compared with the experimental data and the agreement is found to be good. The effect of flow through intakes on normal force and pitching moment is not significant where the effect is significant on axial force. 6 and Vipin kumar 7 on body-intake configurations for measurement of external aerodynamic coefficients. The objective of present study is to find the applicability of the CFD code, PARAS-3D for the prediction of the external aerodynamics of body-intake configurations and also to find the effect of flow through intakes on external aerodynamic coefficients. The details of body-intake configurations, PARAS-3D code and the computational results are presented. Comparison of the CFD results with experimental data is also presented. II. Body-intake Configurations Two configurations were investigated. configuration-1 consists of body with two side-mounted intakes (twin intake configuration) and configuration-2 consists of body with four intakes (cruciform intake configuration). The body consists of ogival nose followed by circular cylinder. The body is identical for both configurations. Diameter of the body is 27 mm. Nose fineness ratio is 3 and slenderness ratio of the model is 15. The intakes are 2-dimensional. Length and span of intakes of both configurations is same. Thickness of intakes of twin intake configuration is twice that of intakes of cruciform configuration. For twin intake configuration, intake entry plane is not facing the body. For cruciform intake configuration, intake entry plane is facing the body. Angle of intake entry plane is 34.4° with respect to flow direction for all he intakes. The details of the configurations are shown in Fig.1. In the flow through condition, the thickness of the intake walls is taken as 0.5mm. III. PARAS-3D code PARAS-3D code is a PARallel Aerodynamic Simulator, which can simulate viscous, turbulent and three-dimensional fluid flow over arbitrary three-dimensional bodies. The grid around the bodies is generated by means of a Rectangular Adaptive Cartesian Mesh (RAM) technique. This code is based on explicit scheme with second order accurate in space and of total variation diminishing (TVD) type, which is $

Novel E glass composites with polybenzoxazine and in situ generating reactive multi branched titanate for low temperature cure and high thermal resistance applications

Abstract: A new class of E glass fabric reinforced polybenzoxazine titanate composites (EBTA) were made with bisphenol F benzoxazine (BZ) and in situ generating reactive multi branched n-butoxy triethanol amine titanate (TEA) chelate in various ratios. The incorporation of TEA into a polybenzoxazine matrix could cause uniform dispersion within the polymer matrix and ring opening of oxazine at lower temperature, which result in an increase of the cross link density, stiffness and hindered network structures responsible for enhancing the thermal and water resistance. The hypothetical chemical reaction between BZ and TEA was understood by studying the reaction between model compounds such as phenol, tetra isobutyl titanate and triethanol amine. FTIR and DSC studies were utilized to optimize the curing studies and the final cure temperature was established for EBTA composites. The DMA analysis carried out on EBTA composites showed improved stiffness, crosslink density and service temperatures (Tg) with uniform phase distribution when compared to the E glass fabric reinforced polybenzoxazine composite. The thermal stability and char yield with TGA analysis, interfacial adhesion with SEM and hydrolytic stability for the EBTA composites using up to 23% of TEA were found to be improved when compared to the polybenzoxazine composite. The flame retardancy of EBTA composites were found to be retained for the V1 class of polybenzoxazine composite. The EBTA composites showed low maximum cure temperature, improved service temperature, cross link density, stiffness, water absorption resistance, thermal stability and char yield when compared to the E glass fabric polybenzoxazine composite.

A Simplified Guidance for Target Missiles Used in Ballistic Missile Defence Evaluation

Abstract: A simplified guidance scheme for the target missiles used in Ballistic Missile Defence is presented in this paper. The proposed method has two major components, a Ground Guidance Computation (GGC) and an In-Flight Guidance Computation. The GGC which runs on the ground uses a missile model to generate attitude history in pitch plane and computes launch azimuth of the missile to compensate for the effect of earth rotation. The vehicle follows the pre launch computed attitude (theta) history in pitch plane and also applies the course correction in azimuth plane based on its deviation from the pre launch computed azimuth plane. This scheme requires less computations and counters In-flight disturbances such as wind, gust etc. quite efficiently. The simulation results show that the proposed method provides the satisfactory performance and robustness.