JOURNAL OF ENERGETIC MATERIALS
Year:2009 | Volume:4 | Issue:1|Papers Count:8

Tate model results have good agreement with practical results and numerical simulations, but it has some differences in initial and final processes of the penetration. For instance, Tate model cannot predict residual length of penetrators appropriately. In this article, a penetration model is demonstrated which is based on the Tate model, Tailor and Hugoniot equations and can predict penetration and residual length of a high velocity penetrator that penetrates in a semi-infinite target. For model validation residual length of a particular penetrator is compared with Walker-Anderson, Tate and numerical analysis results and the accuracy of model prediction is exhibited. Finally in order to explain the practical usage of this study, high efficiency limit of penetration velocity is investigated.

Determining capacitance and coil parameter in electromagnetic forming (EMF) process is one of the common difficulties in industrial applications of the process. In the present paper, an algorithm has been presented in order to calculate EMF device electrical current pulse with various capacitances and coil parameters. At first, an initial guess is considered for angular frequency and capacitance. Then, the effective part of the current pulse is calculated by an iterative computational subroutine using FE method. In this paper, an electromagnetic tube expansion problem, previously analyzed experimentally in the literature, has been studied. The comparison shows an acceptable agreement between numerical and experimental results.

Unsymmetrical dimethylhydrazine (UDMH) is one of the most important and useful liquid fuels. Existence of some problems in using hydrazine has made UDMH a suitable alternative fuel in the smart and long range missiles. Several methods for the synthesis of this compound are reported, but these methods have some drawbacks. In this paper, we report a safe and effective method for the synthesis of high yield UDMH by using dimethyoxytrityl hydrazine as intermediate. In the first step, methylations of NH2 group with dimethylsulfate take place. Finally, DMT group was removed from N, N-dimethyl-N'-dimethoxytrityl hydrazine in non-aqueous condition with ceric ammonium nitrate catalyst to produce high-yield- dry UDMH.

Aging resulting in stabilization is one of the most important and advanced aspects of polymer chemistry. Solid propellants as polymer-based materials deal with aging process as well. This research work has evaluated Dynamic Mechanical Analysis (DMA) for characterization of composite propellant samples during an accelerated aging program. Although there are only a few reports in the open literature concerned with using DMA in aging studies they are not reported inside the country. In this method, the changes in storage module (E) and damping (tand) of the sample during the aging time versus temperature are investigated. Accelerated aging tests at 25, 45, 60, and 70°C were performed for the maximum 8000 h. Finally, we observed that damping efficiency decreases about 12% as a result of thermal aging. The resulted data may be used to determine the aging rate, service time and decomposition mechanism during the rocket storage.

Performance characterization and sensitivity analysis of conic shaped-charge systems are usually studied by utilizing experimental tests. Being time and cost consuming processes, researchers preferred to substitute these methods with faster and cheaper ones such as numerical modeling and simulations. The semi-empirical codes as well as finite element method (FEM) have been developed in order to performing these simulations. Due to the high time consuming manner in analyzing nonlinear analysis, FEM is not of very interest performing analysis especially in primary steps of a design procedure. The semi-empirical codes are widely used as fast computational tools analyzing these problems as well as performing sensitivity analysis. Nevertheless it is to be noted that FE analysis must be considered in more advanced steps of a design procedure. The jet breakup time because of its major role in penetration phase is a key parameter in the analysis of shaped-charge systems. The empirical governing equations of the penetration are dependent to this parameter. Therefore the estimation of the break-up time is an important step establishing a semi-analytical calculation code. In the present paper, the process of conical liner collapse, jet formation and penetration into a steel target is simulated analytically and the results of jet velocity, break-up time and penetration depth are studied using a semi-empirical calculation code. The code is developed on the basis of well-known BASC code assumptions. The jet break-up time calculation is based on some experimental formulas from the literature. Finally, the results obtained from the developed code calculations for a specific type of shaped-charge system are compared with finite element analysis results and also some experimental data. The comparison shows good agreement.

Use of antioxidants in the formulation composite propellants is unavoidable. These materials are added to the propellants to give them stability during storage time. In this paper, different methods of synthesis of A.O.2246 and its phenolic intermediate were investigated and then considering the advantages and disadvantages of these methods and their potential in scaling up, the preferred method for preparation of these materials was adopted. The commonly used procedure for the production of the intermediate 2-t-butyl-4-methylphenol (by reaction of pcresol with t-butyl alcohol in the presence of phosphoric acid) produces by-products whose separation from the desired material needs consecutive basic and acidic extractions followed by recrystalization. In this work, by optimizing the reaction conditions, we have synthesized the intermediate in 99% purity and 95% yield without any need to go through the separation process. Then by reaction of the produced intermediate with formaldehyde in the presence of concentrated sulfuric acid and sodium dodecyl sulfate, A.O.2246 was produced. High yield of the reaction product, mild reaction condition, short reaction time and its potential to scaling up are the advantages of this method.

In a large caliber gun, charge determination has vital significance for gaining maximum muzzle velocity. Geometry and material of grains and charge weight (or number of grains) are important variables for charge determination. Using internal ballistic software, we can determine the appropriate values of these variables. Determining the shape and material of the grain, makes the charging of a projectile possible. In this simulation program, the changes of the shape of the grain and the changes of its material are applied through shape function and changing the burning rate and special force ratios of the propellant respectively. In this article, an internal ballistic model is explained and evaluated. Then, the appropriate charge for a large caliber APFSDS projectile is determined. Finally, by using determined charge, the experimental results are compared against three sets of predictions obtained with the software to show the simulation accuracy.