Wyniki wyszukiwania - BazTech

1

A Study on Creep Behavior of Composite Solid Propellants Using the Kelvin-Voigt Model

Bihari B. K., Rao N. P. N., Gupta M., Murthy K. P. S.

Central European Journal of Energetic Materials

|

2017

|

Vol. 14, no. 3

742--756

EN

A Kelvin-Voigt model consisting of a spring and a dashpot in parallel was applied for the viscoelastic characterization of solid rocket propellants. Suitable values of spring constants and damping coefficients were employed by a least squares fit of the errors to generate creep curves using a Dynamic Mechanical Analyzer (DMA) for composite solid propellants. Three different composite propellant formulations based on HTPB/AP/Al having burning rates of 5 mm/s, 15 mm/s and 20 mm/s were tested under different stress levels varying from 0.1 MPa to 3 MPa and at different temperatures varying from 35 °C to 85 °C. Creep behavior with recovery was studied and analyzed to evaluate the viscoelastic properties. The change in spring constants, representing elastic deformation, was very small compared to the damping coefficients for the propellants studied. For a typical propellant formulation, when the stress level was increased, the spring and damping coefficient both increased significantly whereas for an increase in temperature, they remained nearly constant. However, the ratio E/η was observed to be constant and independent of stress level. It was also observed that the variation of E and η varied linearly with increase in stress whereas their ratio showed a logarithmic variation. A mathematical correlation was developed to evaluate the viscoelastic properties during creep of composite propellants.

2

Statistics of Fragment Dispersion by Explosion in a Fragment Generator Warhead

Dhote K. D., Murthy K. P. S., Rajan K. M., Sucheendran M. M.

Central European Journal of Energetic Materials

|

2016

|

Vol. 13, no. 1

183--197

EN

Understanding the dispersion characteristics of fragments is essential for precise planning of the end game and the neutralization of targets using directional fragment generator warheads (FGW). The authors have carried out experiments to study the spatial dispersion of the fragments in two configurations of FGWs having a circular shaped fragment generating surface. In this paper, the dispersion of the fragments is quantified using the mean and standard deviation of the projection angle. Using the Shapiro-Wilk test, it is verified that dispersion in the projection angle follows a normal distribution. The dispersion of the peripheral fragments is higher due to edge effects. A steeper variation in projection angles is observed for fragments placed at a radial distance greater than 0.7 times the explosive charge radius. These observations are in agreement with the results of Held (1988) for a square shaped fragment generating surface.

3

Directional Warhead Design Methodology for a Tailored Fragment Beam

Dhote K. D., Murthy K. P. S., Rajan K. M., Sucheendran M. M.

Central European Journal of Energetic Materials

|

2015

|

Vol. 12, no. 4

637--649

EN

In this article, the authors present a design methodology for generating a spatially tailored fragment beam with specified velocity and projection angles. The modified Gurney equation was used to estimate the length and diameter of the cylindrical charge to achieve the desired velocity; and the modified Taylor equation was used to arrive at the radius of curvature of the fragmenting disc. The methodology is further explained for generating a rectangular beam of fragments having a velocity of 1500 m/s with a tailored fragment beam of 32° in the azimuth and 20° in the elevation. The warhead had preformed steel fragments of 4 mm diameter arranged in a double layer. The design was validated using the fragment distribution measured experimentally.