فصلنامه مواد پر انرژی
سال ششم شماره 2 (پیاپی 12، پاییز 1390)

The necessity of designing safe structures to withstand an air strike on a ground surface is obvious. In order to meet this goal, the blast characteristics and propagation of intense wave caused by it in discontinues rock media is considered. After selecting a dynamic pulse caused by an airborne bomb, with a specific weight and penetration on the ground surface and calculation of the resulted crater, it is applied, in a radial shape, on the crater surface. Thereby the wave propagation and its damping in a discontinum media is investigated. The rock mass and propagation of dynamic wave in it is modeled using UDEC software. The results show that with increase in the depth of structure, its instability decreases against the blast caused by a bomb with specific weight and penetration. The existence of effective discontinuity also decreases this possibility. Under the same conditions the possibility of the structure stability increases if the slope angle against the line drawn to the center of the blast is about 60 degrees.

In this paper the propagation of detonation waves in high explosives as well as gaseous mixtures are studied by combining the DSD theory and the level set method. In first step, the D-κ and relations for high explosive materials and gaseous mixtures are obtained. Then, using level set method, the detonation front is tracked in different geometries. A good agreement between DSD results and direct numerical simulations is observed for high explosive materials, where the curvature has an important role in detonation dynamic. Nevertheless, for gaseous mixtures the agreement is not as good as high explosives. In order to study the critical diameter problem in gaseous mixtures, the problem of detonation wave diffracting from a channel into an unconfined space is investigated. In this problem, the detonation failure criterion, based on the critical curvature concept, is utilized. A considerable difference between critical diameters which had been predicted by DSD theory and the experimental results is observed. The results indicate that the critical diameter in gaseous compositions (where the unsteadiness and chemical kinetic are more crucial than the curvature) is often underestimated by the DSD theory.

Zeolites are microporous crystalline materials with a uniform pore size distribution on a molecular scale and with high thermal and chemical stability. Zeolite membranes NaA, ZSM-5, Mordenite< NaX and NaY grown onto seeded mullite supports. Separation performance of zeolite membranes were studied for water-dimethylhydrazine mixtures using pervaporation (PV) method. The best flux and separation factor of the membranes were 0.62 kg/m2.h and 52000, respectively, for NaA zeolite membrane. Strong electrostatic interaction between ionic sites and water molecules (due to its polar nature) makes the zeolite NaA membrane very hydrophilic. Zeolite NaA membranes are thus well suited for separating liquid-phase mixtures by pervaporation method. In this study, experiments were conducted with various UDMH–water mixtures (1–20 wt. %) at 25. Total flux for UDMH–water mixtures was found to vary from 0.331 to 0.241 kg/m2.h with increasing UDMH concentration from 1 to 20 wt.%. Ionic sites of the NaA zeolite matrix play a very important role in water transport through the membrane. These sites act both as water sorption and transport sites. Surface diffusion of water occurs in an activated fashion through these sites. The precise nanoporous structure of the zeolite cage helps in a partial molecular sieving of the large solvent molecules leading to high separation factors. A comparison between experimental flux and calculated flux using Stephan Maxwell (S.M.) correlation was made and a linear trend was found to exist for water flux through the membrane with UDMH concentration.

Hydrazine catalytic propulsion system is the most conventional system in satellite orbit control. Dimethyl amino ethyl azide (DMAZ) is a replacement candidate monopropellant for hydrazine in such systems. Catalyst IR/γ-Al2O3 has been reported for decomposition of DMAZ. However, there is no information about performance conditions of the catalyst. For prediction of decomposition ability of DMAZ by the catalyst, several catalysts with various amounts of IR were prepared and characterized. Then, a micro-reactor was designed to evaluate the catalytic activity. The prepared catalysts were tested and examined at various conditions. The results showed that the increase in temperature of catalytic bed and decrease in space velocity led to an increase in catalytic activity. Also, an optimum amount of 42% in IR showed maximum activity at 205 °C of catalytic bed and 2.82 hr-1 of space velocity.

Rupture discs are used as high speed valves in gas guns to study impact and penetration phenomena. These devices are also used extensively in shock tunnels for the study of explosion and shock waves. In the article grooved and ungrooved rupture discs are studied numerically as well as experimentally in order to design an Aluminum diaphragm to be used in a gas gun. Instability and rupture analysis of discs is the main concern in this paper. LS-DYNA software has been used in order to simulate deformation and rupture phenomena. A tester and several diaphragms were constructed and tested in order to empirically determine rupture pressure. Rupture pressure were measured experimentally for ungrooved and grooved diaphragm with 1mm depth. Using experimental data, a semi-empirical relation is developed which delivered approximate rupture pressure for grooved and ungrooved diaphragm. The results of the numerical and experimental investigations were compared and good agreements were obtained.

In this study, BAMO-THF as an appropriate energetic binder was produced. Initially, BAMO as energetic monomer was obtained from Pentaerythritol after three steps reactions. Then, BAMO-THF copolymer was produced via cationic polymerization method using BAMO and THF as monomers, 1,4-butanediol as initiator and Boron triflouride as catalyst. Products obtained from each step were analyzed by FT-IR, 1H NMR, 13C NMR, GPC and CHN analyses. Results indicated that all products (intermediates and BAMO-THF copolymer) are successfully produced with high purity.

In this study, 4 composite layers of plain carbon fiber fabric, plain glass fiber fabric and carbon-glass [carbon-glass-carbon-glass] fiber fabrics, are tested under high speed impact (118 m/s) with flat or half-spherical projectile in impact angles of 0, 30 and 45 degrees compared to the normal impact, and the amount of damage as well as their ballistic limit was studied. Results showed that with increase in the impact angle striked with the flat projectile, the ballistic limit decreased by 30% and the damage area decreased by 36%. Also, with the increase in the impact angle striked with the half-spherical projectile in speed of 118 m/s on 4 layers of carbon fiber fabric and glass fiber fabric, the ballistic limit increased by 25% and the damage area decreased by 40%. The maximum damage area and ballistic limit was in 4 layers of glass fiber fabric and the minimum damage area and the ballistic limit was observed in 4 layers of carbon fiber fabric, that with integration of these 2 fabrics and generating 4 layer fabric of carbon-glass, the high ballistic limit of glass fiber fabric and low damage area of 4-layer carbon fabric is achieved in 4 layer carbon-glass laminate.