JOURNAL OF ENERGETIC MATERIALS
Year:2017 | Volume:11 | Issue:4 (32)|Papers Count:7

In this paper, experimental analysis of ballistic limit velocity of autoclaved aerated concrete (AAC) targets under rigid projectile penetration is presented. Industrial blocks with dimension of 600×250×200 (mm) were cut into 125×125×50 (mm) samples, impacted by gas gun using three different nose shaped projectiles (flat, ogive and conic). In this study damage mechanism and penetration depth were investigated and compared with conventional concrete which revealed significant difference in the initial penetration and cratering phase. Due to difference of weight and initial velocity of the projectiles, initial energy for three- nose shape was measured.. The results show that in low velocity with equal energy, deep penetration has a direct relation with nose shape, but as energy increased, this relation decline which could be found that by rising velocity, shearing mode become dominant. Finally, the result compared and the difference between penetration mechanisms and cratering were discussed and investigated.

In this research, effect of explosive ratio parameter on the interface properties of explosively bonded copper-410 martensitic stainless steel was investigated. Plates were welded in constant standoff distance with different explosive ratios.Optical microscopy, scanning electron microscopy, microhardness and tensile shear tests were carried out. The results showed that wavelength, wave amplitude, and locally melted zones increased by increasing explosive ratio due to more severe plastic deformation in the interface. Hardness was increased in near of the interfaces. Hardness was also increased by increasing the explosive ratio in the copper and steel sides. The tensile shear test result showed that fracture occurred on the copper side, no separation occurred from the interface and strength of interface was more than the copper side.

Ammonium nitrate (AN) is widely used in fertilizers, civilian explosives and military explosives. Due to crystalline phase transitions and density changes of AN at ambient conditions, its usage as oxidizer in solid propellants has some limitations compared to ammonium perchlorate (AP). Several methods have been introduced to overcome these problems. In the present paper, the phase transitions and thermal behavior of AN have been studied. The effects of hydrazodicarbonamide, 2, 4-dinitrophenoxy ethanol, 5, 5-dimethyl hydantoin, nano-MWCNT-COOH and activated carbon with cellulose acetate on the thermal behavior and phase transitions of AN have been investigated by simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA-DSC). The results showed that 5, 5-dimethyl hydantoin, nanoparticles and activated carbon with cellulose acetate can stabilize AN by removing the ANIV ↔ANIII and ANIII ↔ANII phase transitions.

In this research, effective functionality and functionality distribution of three types of HTPB sample are characterized and their reactions with toluene diisocyanate (TDI) have been investigated through the gel point measurement. On the basis of gel point studies concerning the formation of polyurethane networks, the results showed that the effective functionality of three types of prepolymers increases in order HTPB1>HTPB2>HTPB3. Then, polyurethane elastomers of three HTPB samples have been prepared and the tensile test has been performed. It was found that by increasing the effective functionality and CL/CE ratio of HTPB samples, the tensile of corresponding polyurethane elastomer is increased while its strain is decreased. The results of tensile test have been modeled with Mooney-Rivilin equation. Experimental data for Mooney-Rivilin constants were found and have shown that the C1 value of Money-Rivilin equation for polyurethane elastomers based on HTPB1 and HTPB3 are greater than those based on HTPB2. Furthermore, it was found that trapped entanglements and more side chain in HTPB2 resin can be responsible for the high value of C2 in Money-Rivilin equation.Also viscoelastic properties of three types of elastomers are studied and have shown that the less functionality of HTPB samples give lower storage modulus and higher loss factor for corresponding polyurethane elastomers.

Reduction of structural damages due to the blast attacks is the main priorities of civil defence. Since most researches in this field are concentrated on stability and strength increasing of the structures, this paper provides an effective method to blast load mitigation on the structures. Herein, twelve full-scale samples in four groups have been tested under the same weight and stand-off of the explosive. The first group was single RC slabs and other three groups were the same RC slabs with energy absorbing layer: plastofoam, sand and light brittle blocks. Comparison of the experimental results showed that the use of energy-absorbing layers in reinforced concrete slabs, lead to reduce the maximum and permanent displacement at the center of the slab up to 77% and 87% respectively, diminishing the number and thickness of cracks, prevent the scabbing and improve the behavior from severe damage to minor damages. The results also showed that in order to displacement reduction and damage mitigation, the use of the block is preferable to sand and plastofoam.

Ammonium perchlorate is widely used as an oxidizer in the propellant formulation and pyrotechnics. According to military standard, having high purity and free of impurities, such as chlorate, is very important because it affects the performance of ammonium perchlorate. Thus, the removal of impurities in the production of ammonium perchlorate has been highly studied. Herein, the removal of chlorate was investigated via reductive process using metal nanoparticles. Firstly, stabilized Ni/Fe bimetallic nanoparticles (S-Ni/Fe NPs) were synthesized and the structure and size of the particles were determined by XRD, FE-SEM, and EDS. Nano particles were obtained with particle size of 20-50 nm. Prepared nanoparticles were used for the selective removal of chlorate in aqueous ammonium perchlorate. The main factors that affect the removal process such as pH, reaction temperature, reaction time and amount of nanoparticles were considered and the optimum values were determined. Under optimal conditions, chlorate in the presence of perchlorate, with 1.5 molar ratio, showed a removal of 100 percent, while the perchlorate had been removed to a very small amount. The proposed method for the removal of chlorate in a saturated solution of ammonium perchlorate, which is used in the production process, showed satisfactory results.

In the present study, dynamic behavior of elevated liquid storage tank subjected to blast loading is investigated through a three dimensional (3D) finite element (FE) model of a steel water storage elevated tank with applying different tank aspect ratios, percentages of water stored in the tank and different tank wall thickness using the FE software ABAQUS. The coupled Euler–Lagrange (CEL) formulation in ABAQUS has been adopted herein which has the advantage of considering the coupling of structural mechanics and fluid mechanics fundamental equations. The maximum hoop stress, shear stress and plastic strain in the tank wall and displacement, base shear and moment in the whole model have been studied under a free air blast arising from an 80 kg TNT for 5 m standoff point distance. The maximum hoop stress and shear stress in the tank wall and displacement, base shear and overturning moment of elevated tank have been studied. It is observed that stresses and strain increase with decreasing percentages of water stored in the tank and decreasing wall thickness.Displacement, base shear and moment decrease with increasing of percentages of water stored in the tank.