Articles written in Sadhana
Volume 44 Issue 7 July 2019 Article ID 0160
Magnesium/Teflon/Viton or MTV pyrotechnic composition has been widely preferred to prepare decoy flares as countermeasures against heat seeking Infra-red (IR) missiles. Though MTV for military applications are available in the global market, the manufacturing process and performance characteristics of these flares have not been explicitly defined. The pellets which are an essential sub-assembly of the flares need to be extensively studied to develop these flares for military applications. The study paper attempts to optimise the density of compacted 50 mm diameter cylindrical pellets. The pyrotechnic composition is initially subjected to various sensitivity tests namely impact, friction and spark to assess the threshold values of initiation of this composition. Three levels of process parameters for pelleting have been considered and L27 array has been selected to represent the process parameters namely charge mass (A), applied load (B), dwell time (C) and their interactions. The Taguchi robust experiment method arrived at the optimal result as A1B3C3 (100 g of charge mass, 8 tons of applied load and 20 s of dwell time). Analysis of Variance (ANOVA) highlighted that parameters A and B significantly influenced the density of the pellets. Finally, general regression equation was derived with R2 value of 0.94.
Volume 45 All articles Published: February 2020 Article ID 0045 Original Article (Mechanical Sciences)
Infra-red decoy flares constituting of Magnesium, Teflon and Viton or MTV, is the most widely acceptable off-board counter measures among majority of the defence forces across the world. These flares are essentially pyrotechnic compositions operating in the range of 3–5lm wavelength owing to the selective emission of the combustion products (MgO, MgF₂ and oxides of carbon namely CO and CO₂). However, literature on manufacturing techniques and performance characteristics of standard configurations flare pellets developed and supplied by few firms globally is somewhat restricted. Hence, this study is an attempt to evaluate the performance of mechanically pressed 50 mm diameter cylindrical MTV pellets. While varying the process parameters viz. charge mass and applied load for pelleting, the cross-sectional area of the pellets and dwell timeof applied load have been maintained constant. With increase in applied load, elastic/brittle fracture of the particles occur which increases surface area of contacts between particles. The optimum density was achieved at 8 tons of load. Similarly, the improvement in density with increase in charge mass was observed till L/D ratio of unity was achieved. SEM images confirmed the increase in contact surfaces and reduction in size of particles owing to elastic/brittle fracture. With increase in applied load, the available surface area decreased and there wasa conspicuous increase in burn time. With increase in charge mass, the quantity of pyrotechnic mixture available for burning increased leading to increase in burn time.