Compressible material

Cork compositions 250 Low cost. Truly compressible materials which permit substantial deflections with negligible side flow. Conform well to irregular surfaces. High resistance to oils good resistance to water, many chemicals. Should not be used with inorganic acids, alkalies, oxidizing solutions, live steam. 

When an isotropic material is subjected to planar shock compression, it experiences a relatively large compressive strain in the direction of the shock propagation, but zero strain in the two lateral directions. Any real planar shock has a limited lateral extent, of course. Nevertheless, the finite lateral dimensions can affect the uniaxial strain nature of a planar shock only after the edge effects have had time to propagate from a lateral boundary to the point in question. Edge effects travel at the speed of sound in the compressed material. Measurements taken before the arrival of edge effects are the same as if the lateral dimensions were infinite, and such early measurements are crucial to shock-compression science. It is the independence of lateral dimensions which so greatly simplifies the translation of planar shock-wave experimental data into fundamental material property information. 

Wise, J.L. and L.C. Chhabildas (1986), Laser Interferometer Measurements of Refractive Index in Shock-Compressed Materials, in Shock Waves in Condensed Matter (edited by Y.M. Gupta), Plenum, New York, pp. 441-454. 

Coherent block of granular plastic molding compound or of fibrous mixture with or without resin. Prepared by sufficiently compressing material, forming a block that can be handled readily. 

Numerous resistance measurements have been carried out under high-pressure shock compression [79D01]. Most of the work has been motivated by the desire to develop stress gauges to measure pressures in shock-compressed materials. Other measurements were undertaken to determine critical pressures to induce phase transformations. Although most of the work is not carried out in sufficient detail to relate resistance observations to defect characterizations, excess resistance at given shock pressures is observed in every case compared to comparably loaded static pressure observations. The presence of residual resistance for times after the loading is removed provides explicit evidence for irreversible changes in resistance due to defects. 

Beeause of its emphasis on eonsistent thermodynamies, the csq eode does not permit the use of a P-a model for the erush-up behavior of the powder. Thus, it was neeessary to draw upon the experience in the one-dimensional simulation to select appropriate shock-compression materials behaviors. The... 

The exudation products appeared to be a mixt of wax sealer and black asphalt, and contained no expl. The use an inert, compressible material in place of the inert wax in GP bomb tail sections, along with better sealing, has been successful in overcoming such exudation (Ref 32)... 

A. Y. Liu and M. L. Cohen, Structural Properties and Electronic Structure of Low-Compressibility Materials P-silicon Nitride and Hypothetical Carbon Nitride (P-C3N4), Phys. Rev. B, 41(15), 10727-34 (1990). 

Compressibility is indirectly related to the relative flow rate, cohesiveness, and particle size of a powder. A compressible material will be less flowable, and powders with compressibility values greater than 20-21% have been found to exhibit poor flow properties [69]. 

Furnace black-reinforced EPDM and NBR blends were compounded with different concentrations of azodicarbonamide foaming agent to produce EPDM and NBR foamed composites. All the mechanical parameters measured were found to decrease as the foaming agent concentration and/or temperature increased. The stress-strain results were discussed with reference to the continuum mechanics theory for compressible materials. 16 refs. 

Up, to the pressure p and specific volume v of the compressed material. The relationships are given by the Rankine-Hugoniot Equations ... 

This new set of invariants was introduced by Blatz and Ko19 in order to discuss compressible materials under relatively small deformations. 

Valanis and Landel20 suggested that a possible form of W for compressible material would be... 

Analysis of the filtration of a compressible material is treated in Example 11.4. 

Muraour et al (Ref 3) think that the reason for MF not to detonate when ignited is that it burns on the surface only and the hot gases cannot penetrate inside the mass of expl, while in the case of not highly compressed material, they easily penetrate inside the mass, thus causing the deton. If this theory is accepted, then it would be understandable why LA cannot be dead-pressed. This is because when it is touched with a hot wire, it detonates without previous combustion. Diazodinitrophenol, Ag azide, Hg Azide, Ag Fulminate also cannot be dead-pressed... 

Finally, compression-extrusion testing involves an extrusion cell commonly used for weakly structured, homogeneous food products. This apparatus consists of a piston that is forced into a cylinder open at one end and containing the product (Figure H2.2.5). Beyond the point of rupture of the food, the compressed material is forced to flow back through the annular space between the piston and the cylinder (Bourne, 1976 Edwards, 1999). The gap between the piston and the cylinder is called the annulus (Bourne, 1982). Variation in the annulus width results in variation in the force required for extrusion (Bourne, 1982). 

The most important new conclusion of the theory turned out to be the fact that in front of the zone of reaction products, whose state is determined by the Chapman-Jouguet rule, there is a certain amount of initial combustible material compressed by the shock wave. In this compressed material the pressure is approximately twice as high as the final pressure. The significance of the existence of a zone of such increased pressure is obvious not only for the theory, but also for accident prevention. Many studies are devoted to experimental proof of the existence of this zone. Perhaps still the most convincing and practically useful is a paper written by Ya.B. in collaboration with S. M. Kogarko which confirmed the conception of an increased pressure zone (28). Concrete perceptions of the conditions of the chemical reaction have changed substantially (see the commentary to 28). However, Ya.B. s... 

As discussed in Vol 7, HI 79, the Hugoniot equations (or more correctly Rankine-Hugoniots), the simultaneous measurement of any two of the above variables is sufficient to determine all the rest provided conditions ahead of the shock (u0s P0, p o> Eo To) are known. Thus, for mathematical convenience but closely approximated in reality, the shock abruptly divides virginal (unshocked) material from shocked (compressed) material. For the reader s convenience, because we will refer to them frequently, this is illustrated in two graphs taken from the above Vol 7 article. They show the transmission of a shock from one material to another (script S s are shocks and script R s are rarefactions)... 

Material flow and compressibility. A free flowing, highly compressible material such as microcrystalline cellulose may be used for drugs with poor flow or compressibility properties. 

In view of the possibility of random free-radical scission of some covalent bonds, despite a great deal of dissipation of energy in the same sample, this repolymerization may be the likely interpretation, as the effect could result from recombination (or rather free-radical condensation) in the compressed material. 

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