Energy Input with No Compression

In order to characterize the state of a material following constant volume heating, the pressure-energy coupling relationship must be known. The relationship is determined through the Gruneisen coefficient, T, of the material, as it appears in the Mie-Gruneisen equation of state [51], and can be written in 

P is the pressure, Fis the specific volume, and is the specific internal energy. The Mie-Gruneisen equation is generally employed in finite-difference com- 

An effective Gruneisen coefficient can be defined for solid materials, including substances such as granular explosives, by 

The effective P may be determined with the electron beam apparatus. When the sample (slab geometry) is thick enough to absorb all of the incident electrons, a compressive stress wave propagates from the irradiated region into the sample bulk. A transducer, located just beyond the deposition depth, may be used to record the stress pulse. Alternatively, the displacement or velocity of the rear surface of sample may be observed optically and used to infer the initial pressure distribution from the experimentally measured stress history. Knowledge of the energy-deposition profile then permits the determination of the Gruneisen coefficient. 

Experiments with lead azide and KDNBF were conducted using the above technique and a buffer of fused quartz between the sample and the gauge [51]. Initiations occurred in most of the tests, especially with lead azide and prevented the determination of the sound speed for lead azide, but a value of 3.0 0.2 km/sec was obtained for KDNBF. 

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