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.

Thermal response tester for qualification of detonators

Abstract: Detonator plays a critical role in ignition chain of aerospace vehicle. As it is a single shot device initiating ignition chain, it has to cater two contrary requirements i.e it should be Safe against unintended initiation and reliably function upon receipt of intended command. Detonators being single shot devices, the full functional testing is not feasible as it calls for consumption of device itself by test firing. Thus in addition to measurement of few electrical parameters & non-destructive tests (NDT), reliability of the lot is mainly assessed from performance of few randomly selected detonators test firing from that batch. This paper deals with the category of detonator that is initiated with electrical current pulse and thermal response testing of such detonators using the developed thermal response tester. Tester helps in revealing poor thermal contact of electrical bridge wire with initiating explosive and imperfections in bridge wire and soldering. Tester isolates the defective detonators and gives insight in to type of defects which can be used for taking corrective measures in future.

Studies on thermal stability and life estimation of epoxy adhesive by thermogravimetric analysis for high-temperature applications

Abstract: Structural epoxy adhesive was investigated for its thermal stability and degradation behaviour in a thermo-oxidative environment by thermogravimetry analysis (TGA). Non-isothermal TGA was performed at temperatures between 30 and 600°C utilizing different heating rates. The ageing characteristics of material were determined by an accelerated ageing study using isothermal TGA at different temperatures for 5% threshold conversion. The activation energies from both non-isothermal TGA and isothermal TGA were estimated and the activation energy values for 5% degradation from both the methods were in good agreement. The epoxy adhesive with titanium dioxide as filler showed a shelf life exceeding 13 years at ambient conditions (27°C). Additionally, the lap shear strength of the adhesive joint was also tested after treating the samples at 70°C with 90% relative humidity to evaluate the hydrothermal effect on adhesive joint.

Fiber Laser Cutting of Nimonic C263 Alloy and Investigation of Surface Integrity

Abstract: Nimonic C263 is a super alloy which contains more than 50% nickel, and is mainly used in gas turbines and internal combustion engines. The present study deals with the fiber laser cutting of Nimonic C263 super alloy using nitrogen as assisting gas. Several experiments were performed by varying the process parameters, such as cutting speed, laser power, gas pressure, position of focus point with respect to the top surface of the workpiece and duty cycle, to observe their influences on the cut-surface integrity. The prepared samples were characterized by FESEM examination, microhardness test, optical microscopy and XRD technique. The average kerf width, heat-affected zone and surface roughness values varied from 201 to 261 µm, 7.96 to 9.30 µm and 2.02 to 3.42 µm.

Galvanic Interactions of 15CDV6/MDN138 & 15CDV6/MDN250 Alloys in Natural Seawater

Abstract: The galvanic corrosion behavior of the metal combinations 15CDV6/MDN138 and 15CDV6/MDN250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI’s Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN138, MDN250, and 15CDV6 of the individual metal, the galvanic potential and galvanic current of the couples 15CDV6/MDN138 and 15CDV6/MDN250, were periodically monitored throughout the study period. The calcareous deposits on MDN138 and MDN250 in galvanic contact with 15CDV6 were analyzed using XRD. The electrochemical behavior of MDN138, MDN250, and 15CDV6 in seawater was studied using an electrochemical work station. The surface characteristics of MDN138 and MDN250 in galvanic contact with 15CDV6 have been examined with a scanning electron microscope. The results of the study reveal that the galvanic protection offered by 15CDV6 to MDN250 and MDN138 in natural seawater amounts to 93% and 98%, respectively, implying that the galvanic protection offered by 15CDV6 is continuous and effective, which has been further evinced from the adherent nature of the calcareous deposit film comprising compounds such as CaCO3 (calcite, aragonite, and vaterite), MgCO3 (magnesite), Mg(OH)2 (brucite), and MgO (brucite).