Initial Velocities of Fragments from A Cylinder Structure
Mafa Wang (College of Science, National U), fangyun Lu (), Chen R (NUDT China), banghai Jiang ()
Joint session: Mechanics and Dynamics of Periodic Structures and Dynamic Behavior of Materials
Tue 4:20 - 5:40
Salomon 101
The Gurney formula based on the conversation of energy was the earliest and most well-known formula for estimating the fragments velocity from bombs. And this formula gives the same velocity for all fragments. However, with the appearance of the concept of asymmetrically initiated warheads, it has been noticed that Gurney formula needs to be developed. The most well-known formula was proposed by M. Held. Considering the distance L from the initiation position to the fragments, he modified the ratio of charge mass to metal casing mass in Gurney formula with L/R, where R is the radius of charge. However Held’s formula estimates fragments velocity in target direction well, while it is not good enough in other directions. In this paper, the cylinder structure warhead is assumed to be long enough so that the boundary effect at both ends of the structure could be ignored. According to the characteristics of fragments in experiments, we proposed a new correctional function of ratio in Gurney formula. In our correctional function, the ignition position and the azimuth angle are the two important variables. And there is a coefficient k as the modified parameter of other factors. The formula is proposed to evaluate velocities of the fragments from cylinder structures in azimuth plane. Comparing with published data, the results calculated from our formula show good agreement with experimental data. In addition, the relationship between the coefficient k and the ratio has been discussed and it is found that the relationship fits a parabola well. Therefor, when the ratio is known, the velocity of fragments from cylinder structures can be calculated by our formula. The formula can also be used to calculate the energy distribution on azimuth angle. And the results show that half of the fragment energy will concentrate on the range of ±63° from the target direction when is equal to1.0. It means that the energy will effectively concentrate on target direction.