International audienceLow velocity impacts on energetic materials induce plastic deformations and sliding friction which can lead to ignition. If some ignition criteria have been proposed, the remaining difficulty is to characterize the mechanical behavior of the material when submitted to the corresponding solicitations (high pressure and high strain rate). Thus, a technique based on the Split Hopkinson Pressure Bars system is proposed to carry out a triaxial compression test. A cylindrical specimen is placed into a confining ring and is compressed by the system of bars. The ring prevents the radial extension of the specimen and creates a lateral confining pressure. The material and dimensions chosen for the ring maintain a constant radial pressure during the test. Some tests were carried out on an inert aggregate material and proved the validity of this experimental device. The experimental data processing shows the influence of both the pressure and the strain rate. The shear stresses, which contribute to thermal dissipation and then to the ignition threshold, increase according to the pressure
The text in the present document is the same as in the published article, page layout is different. v2: The bibliographical data for one reference (previously marked as submitted and published since then) has been updated.
This paper describes the development of a numerical homogenization tool adapted to TATB-based pressed explosives. This is done by combining virtual microstructure modeling and Fourier-based computations. The polycrystalline microstructure is represented by a Johnson-Mehl tessellation model with Poisson random nucleation and anisotropic growth of grains. Several calculations are performed with several sets of available data for the thermoelastic behavior of TATB. Good agreement is found between numerical predictions and experimental data regarding the overall thermal expansion coefficient. The results are shown to comply with available bounds on polycrystalline anisotropic thermoelasticity. Finally, the size of the representative volume element is derived for the bulk, shear and volumetric thermal expansion moduli.
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