PSI - Issue 14

Sukamal Adhikary et al. / Procedia Structural Integrity 14 (2019) 127–133 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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to be always sustained which demands high structural integrity of the pellets. The factors which are likely to influence the quality of the pellets during mechanical pressing can be listed as:

 Shape of pellets  Size of pellets  Charge mass used for pelleting  Load applied for compacting of powder mixture  Dwell time of the load applied .

The flare dispensers of the aircrafts are of cylindrical or rectangular in shapes. The sizes available in cylindrical c onfiguration are 26 mm, 50 mm, etc. whereas for rectangular configuration variants are 1”x1”x8” and 2”x1”x8” flares. To compact the pyrotechnic mixture into pellets with constant cross -sectional area of approx. 50 mm diameter, a hardened steel mould and piston is fabricated as shown in Fig.1. The cross-sectional area and the cylindrical shape of the pellets have been maintained constant since they are compacted in the mould with fixed cylindrical cavity. The length of the pellets varied depending on the process parameters.

F ig. 1 Top View of Mould and Piston

The pelleting operation was performed in a controlled environment with ambient temperature maintained at 24±1°C at a relative humidity maintained within 50±5% through utilisation of industrial de-humidifiers. The pelleting process is as depicted in Fig. 2.

Piston to compress the powder Mould to compress the powder into pellets Electro-Hydraulically operated piston for application of constant load on powder

End cap to retain powder mixture during compressing and to provide recess for extraction of pellets

Fig. 2 Compacting of powder into pellets

The pellet has grooves both along the length as well as the end surfaces to enhance the burning area of the pellets. The effective cross-sectional area is calculated as 16.6 sq cm. The length of the pellets depends on charge mass of the mixture, external load applied for compacting the mixture and the dwell time of the applied load. Three