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: Turbulence & Mach number. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

On the occurrence of dynamic strain aging in C-103 Nb based alloy

Abstract: In this study, the tensile properties of C-103 Nb based alloy were evaluated in the temperature range between room temperature (RT) and 1200 °C using Gleeble test system at the strain rate of 10 −2 s −1 . The presence of well-defined serrations and temperature insensitivity of 0.2% yield strength confirmed the occurrence of dynamic strain aging (DSA) from RT to 1200 °C. However, the DSA was found to have predominant effect only up to 900 °C, beyond which dynamic recovery and oxidation influenced the tensile properties. Fractography revealed that the alloy had undergone intergranular fracture, which was attributed to the DSA in the temperature range of 600–900 °C and oxidation in the temperature range of 1000–1200 °C.

High-temperature stability of yttria-stabilized zirconia thermal barrier coating on niobium alloy—C-103

Abstract: Thermal barrier coatings (TBCs) of yttria-stabilized zirconia (YSZ) of different thicknesses with an intermediate bond coat were deposited on C-103 Nb alloy using the air plasma spraying technique. The coatings were subjected to rapid infra-red (IR) heating (∼25°C s−1) up to ∼1250°C and exposed up to 100 s at this temperature with heat flux varying from 55 to 61 W cm−2. The TBCs were found to be stable and intact after the heat treatment. In contrast, at the same conditions, the uncoated C-103 alloy specimen showed extensive oxidation followed by weight loss due to spallation. A maximum temperature drop of ∼200°C was observed on the opposite side of the coated alloy with 600 μm YSZ coat; as against negligible temperature drop in case of bare alloy specimen. The temperature drop was found to increase with the coating thickness of YSZ. The coatings before and after IR heating were investigated by scanning electron microscopy, X-ray diffraction, electron probe microanalysis, microhardness and residual stress measurements in order to understand the effect of thermal shock on the properties of the TBC. On account of these high-temperature properties, YSZ coating along with the bond coat is expected to find potential thermal barrier coating system on niobium alloys for supersonic vehicles.

Damping Coefficient Prediction of Solid Rocket Motor Nozzle Using Computational Fluid Dynamics

Abstract: Numerical simulations are carried out to evaluate the nozzle damping of rocket motors. A subscale cold flow experimental condition where nozzle damping coefficients are evaluated through the pulse decay method is taken as a validation case. The flowfield of the motor is simulated by solving three-dimensional Reynolds-averaged Navier–Stokes equations using commercial computational fluid dynamics software. The trend of the pressure decay in the head end is well captured for different values of port-to-throat area ratios, and a very good match is obtained between the computed and experimental values of the nozzle decay coefficient. Validated methodology is used to evaluate the damping coefficient of a burning solid rocket motor with composite propellant.