JOURNAL OF ENERGETIC MATERIALS
Year:2008 | Volume:3 | Issue:1|Papers Count:7

Excavation of trenches by blasting is an important application of explosives. The number of pipeline trenches blasted during the recent years has increased in many countries. However, excavation of narrow trenches by blasting has had limited application. The intention of this study was to assess the feasibility of shallow and narrow trench excavation in rock media by blasting. One major application of narrow trenches is the placement of fiber optic communication cables. This paper presents the results of a blasting research work on construction of such channels. As a result of this work, a channel, 40 cm in width and 90 cm in depth, was excavated successfully. The specific charge used varied between 1.66 - 2.89 kg/m3 using gelatin dynamite as explosive charge. The initiation devices were of short delay Nonel, electric detonators (instantaneous and half second), and detonating cord (5gr/m & 10gr/m). The nominal burden was 50Cln and the effective burden was 43.8 cm. The blast hole spacing and sub drilling were 48 cm and 20 cm, respectively.

In this paper five new amine salts of NTO have been prepared and characterized. Dimethyleguanidine, diethylegunidine, melamine, cyclohexamethylentetramine, and cemicarbazide are the amines that have been used in the preparation of the NTO salts. These NTO salts were characterized by 1HNMR, 13CNMR and IR spectroscopy. Some of the explosive properties such as impact and friction sensitivity of the NTO salts were investigated by standard methods. The results obtained indicated that these salts are less sensitive to impact than NTO while having the same friction sensitivity as NTO. The thermal analysis of these salts was done by DSC method, and the obtained temperature exotherm indicated that they are of suitable thermal stability.

Gel propellants are a modified form of liquid propellants. Some of their advantages, compared with liquid propellants, are better safety, lower vapor pressure, loading ability of solid energetic materials and easier storability. In this paper, unsymmetrical dimethyl hydrazine (UDMH) was gelled with the use of methyl cellulose (Me) gellant. The rheological studying of gels showed a better behavior for the which containing 7.5 percent of the gellant. The rheological results were in good agreement with a modified power law model in various temperatures. The gels showed good stability under 500 g acceleration for 30 minutes.

Composite modified double base propellants (CMDB) are made by adding high energetic materials to double base propellants. There are three kinds of CMDB propellants: The first type contain AP and Al the second type are, smokeless propellants containing nitramines such as HMX and RDX, and the third type are high energy propellants containing Al, AP. HMX or RDX. In this paper nitramine CMDB propellants are under consideration. CMDB propellants were made via extrusion method by adding RDX to the double base propellants formulation. The effect of RDX addition on specific impulse, burning rate and mechanicalproperties were studied and the results were compared with a specific reference double base propellant. The results showed that addition of nitramines to double base propellants enhances both specific impulse (Isp), and density of the propellant while decreasing its burning rate and mechanical properties.

The interest of using geo-materials as an ordinance barrier has provided the motivation for studying projectile penetration into soil covered concrete targets for many decades. Protection of sensitive concrete structures against projectile penetration is usually accomplished by using soil layers. One of the main problems is how to estimate and determine the thickness of the covered material and at the same time calculate the crater depth of the concrete when subjected to high velocity projectiles. The aim of this paper is to determine the crater depth of an ogive-nose shape steel projectile penetrating into a concrete target covered with soil. To achieve this objective spherical cavity expansion theory is employed and an analytical model for penetration depth is developed.Also, penetration process into soil covered target is simulated using LS- DYNA capabilities. The results of the simulation and analytical formula are compared and a good agreement is recorded.

In this paper, penetration of the anti-ricochet teeth of conical projectiles into thin metallic targets under oblique impact has been theoretically examined and analytic model has been proposed for it. The failure by conical projectile is assumed to be asymmetric pedaling and the analysis is performed by using the energy balance between initial energy and work done in penetration. The whole work done in penetration consists of the required work for plastic deformation Wp, the work for transferring the material to new a position, Wd, the work for bending the petals, Wb and the work for penetration of the teeth, Wt.The results obtained from the analytical model for the penetration of the anti-ricochet tooth and the theoretical and empirical results of the other work during penetration have been compared and discussed.

In the present research, the effects of side injection from nozzle wall into the main flow ql combustion chamber exit are studied. The side jet flow causes some asymmetry in flow field and consequently leads to several variations in velocity and thrust vector of exit gas flow and pressure distribution on nozzle divergent wall. Interactions of these two flows generate various physical phenomena such as bow shock in front of injection area. The present paper explains the effects of this wave shock and demonstrates the variation of pressure and velocity distribution in a number of cross sections of nozzle flow field. In addition, trend of' pressure, temperature, density and mach number curve along three longitudinal lines on nozzle wall are exhibited. Moreover, variation of the physical properties of flow within shock wave position and injection area is investigated.