Impact fracture behaviour of double-base gun propellants

The geometric burning law of gun propellants is widely used in computer codes used for the simulations of the internal ballistics of guns. However, the results of closed vessel tests prove that the burning process of some propellants deviates from the geometric law. Validation of the hypothesis that observed deviations can be attributed to the cracking of propellant grains was the aim of this work. In order to verify the hypothesis, three types of gun propellants were chosen with considerably differing mechanical strengths: a single-base propellant, a double-base propellant, and a composite propellant. The mechanical properties of the gun propellants were tested using a quasi-static compression method with strain rate values of the order of 0.001 s−1 and the Split Hopkinson Pressure Bar technique with the strain rate in the range of 1000–6000 s−1. The mechanical responses of the propellants were assessed on the basis of the true stress–strain curves obtained and from the point of view of the occurrence of cracks in the propellant grains specimens. Moreover, closed vessel tests were performed to determine experimental shape functions for the considered gun propellants. Juxtaposition of the stress‒strain curves with the experimental shape functions proved that the observed deviations from the geometrical burning law can be attributed mainly to the cracking of propellant grains. The results obtained showed that the rheological properties of propellants are important not only from the point of view of logistical issues but also for the properly controlled burning process of propellants during the shot.

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Comparison of the fatigue and impact fracture behaviour of five different steel grades used in the frog of a turnout

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409713511078 ◽

2013 ◽

Vol 228 (6) ◽

pp. 603-610 ◽

Cited By ~ 7

Author(s):

Sven Eck ◽

Heinz Oßberger ◽

Uwe Oßberger ◽

Stefan Marsoner ◽

Reinhold Ebner

Keyword(s):

Fracture Behaviour ◽

Impact Fracture ◽

Steel Grades

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Impact Fracture of Composite and Homogeneous Nanoagglomerates

Journal of Nanomaterials ◽

10.1155/2008/125386 ◽

2008 ◽

Vol 2008 ◽

pp. 1-7 ◽

Cited By ~ 6

Author(s):

S. J. Antony ◽

R. Moreno-Atanasio ◽

J. Musadaidzwa ◽

R. A. Williams

Keyword(s):

Kinetic Energy ◽

Impact Loading ◽

Fracture Behaviour ◽

Time Lag ◽

Impact Fracture ◽

Initial Kinetic Energy ◽

Normal Impact ◽

Fracture Characteristics ◽

Hard Shell ◽

The Moment

It is not yet clear on whether the fracture characteristics of structured composite capsules and homogeneous nanoagglomerates differ significantly under impact loading conditions. Experimental measurement of impact fracture properties of such small agglomerates is difficult, due to the length and time scales associated with this problem. Using computer simulations, here we show that nanoagglomerates are subjected to normal impact loading fracture within a few nanoseconds in a brittle manner. The restitution coefficient of the nanoagglomerates varies nonlinearly with initial kinetic energy. The fracture of nanoagglomerates does not always happen at the moment when they experience the maximum wall force, but occurs after a time lag of a few nanoseconds as characterised by impact survival time (IST) and IST index. IST is dependant on the initial kinetic energy, mechanical and geometric properties of the nanoagglomerates. For identical geometries of the capsules, IST index is higher for capsules with a soft shell than for these with a hard shell, an indication of the enhanced ability of the soft nanocapsules to dissipate impact energy. The DEM simulations reported here based on theories of contact mechanics provide fundamental insights on the fracture behaviour of agglomerates—at nanoscale, the structure of the agglomerates significantly influences their breakage behaviour.

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