فصلنامه مواد پر انرژی
سال شانزدهم شماره 3 (پیاپی 51، پاییز 1400)

Due to low electrical conductivity of liquid fuels, electrostatic accumulation is a problem in production, transportation and storage of the fuels. Electrostatic accumulation more than ambient ionization energy leads to electrical spark which causes firing and/or fuel tank explosion. Therefore, the electrical conductivity is a key parameter in fuels or flammable solvents. In this research, the apparatus cell for electrical conductivity measurement of liquids was firstly manufactured based on DIN51412-1 standard. Due to some problems in standard cell such as dependency of electrical conductivity on sample volume, chemical leakage, high volume consumption of sample, difficult cleaning of the cell and carrying problems because of size and weight, a new cell was designed based on submerging method and manufactured. The new cell performance was calibrated with various solvents like toluene, hexane and also JP-8 and tetralin as aviation fuels. Then, the conductivity of each solvent and fuel was measured and compared via the standard and new cells in the presence of antistatic Stadis 450. The measuring error was less than 0.5%.

It is very important to study the collision of high-energy material HMX in the form of simulations in order to increase safety and prevent a possible explosion, as well as to increase the quality of the product, in situations that practical testing may be very dangerous.
In this study, due to its high consumption in the military industry and the important role of the size of the material in military equipment, the high-energy HMX material has been used to simulate and evaluate the results. In this article, the energy production rate during the breakage of energetic solid particles in the size of 40 to 150 microns has been investigated. The purpose of this study in the first step is to find the optimal operating conditions in the breakage machine and then to investigate the various parameters caused by the collision of particles of energetic materials during breakage in the introduced jet mill machine. Therefore, in this study, first the designed jet mill in different operating conditions (different inlet pressures) was simulated and investigated using the DPM model. Gas flow behavior, particles moving path and HMX particle temperature were simulated by Ansys-Fluent software. The results showed that The operating pressure of 4 (bar) provides the possibility of maximum breakage in the jet mill machine without the risk of explosion.

In this study, some granulated and pressable formulations based on coating of pentaerythritol tetranitrate (PETN) explosives with high impact polystyrene polymer (HIPS), Viton fluoroelestomer and paraffin wax were developed. Thereafter, mechanical strength of pressed formulations and transition temperature of binders were evaluated using uniaxial compressive strength test and differential scanning calorimetric (DSC) method, respectively. Also, the effect of PETN particle size distribution on compressibility, mechanical strength, density and particle size of pressed samples based on HIPS binder were statistically studied and optimized using mixture design of experiments by Minitab software. In the optimized experimental conditions, the compressive strength and elastic modulus for PETN/HIPS mixture at ambient temperature and at the concentration of 4.0 wt.% of the binder, were 15.0 and 91.1 MPa, which is better than formulations based on expensive Viton polymer and paraffine wax. By using HIPS binder, increasing the amount of PETN particle size <150 μm, mechanical strength of pressed samples decrease, and also particle size distribution in the range of 150-300 μm , leads to production of better formulations.

Sandwich panels are common structures for absorbing explosion energy and used as an explosion shield. In this paper, the performance and dynamic response of a new type of metal and circular sandwich sheet structures as blast energy absorbers with radial tube cores under blast load are investigated. Analytical and experimental methods have been used to evaluate the dynamic response of the sandwich panel structure. In the analytical method, the response of the structure is divided into three separate and consecutive time stages. The first stage includes the interaction of structure and fluid, the second stage is the compression and crushing of the core and the third stage is the dynamic response and bending of the whole structure of the sandwich panel. Using the basic laws of mechanics, such as the laws of mass and momentum conservation, the analytical response of the deformation and the governing equations have been formulated, and a closed form equation for the maximum deflection has been obtained. The experiments were performed by making sandwich panels under the blast load and by free blasting method in order to evaluate and validate the analytical results. The results are compared and there is good agreement between the results in analytical and experimental methods. The average difference between the results of analytical and experimental methods is 18%.

In this research, a new and reliable model for predicting the thermal decomposition temperature of energetic crystals based on structural factors using multiple linear regression (MLR) method is presented. Descriptors used in this model include the ratio of the number of hydrogen atoms to carbon, the number of double bonds, the number of N = N groups, the ratio of aromatics (ARR), the number of 10-membered rings, the ratio of the number of benzene rings to the total number The rings and the number of molecular fragments is N-N. The coefficient of determination of the obtained results was equal to R2= 0.949. Also, the predictive power of the proposed model was evaluated by cross-validation method, which shows the results of Q2LOO = 0.950 and Q2LMO = 0.953, indicating the high predictive power of the model Root mean square deviation (RMSD) and absolute average deviation (AAD) for the proposed model were 10.36 and 8.51 Kelvin, respectively, for 28 high-energy crystalline compounds as a series of training data, indicating the ability to Good model reliability. Also, the validity of the model was evaluated from the external validation method for 9 other energetic crystalline compounds as an experimental series, and the results showed that the RMSD and AAD are equal to 16.61 and 13.63 Kelvin, respectively. . Finally the comparison between the obtained results with similar results based on artifitial neural network is reported.

In the present study, two-dimensional simulation of blast wave in a barrier and unobstructed environment using computational fluid dynamics (CFD) has been performed by finite volume method and dynamically. For this purpose, the characteristics of explosive matter and the dimensions of the obstacles in the blast environment have been entered in open source software and CFD simulation has been performed. Detonation potential energy is applied with the energy source term approach in simulation. For this purpose, a new solver has been created in open foam software with sonicFoam solver modification. Also, the source term presented in past researches has been modified in order to achieve more accurate results. Two models of k- ε turbulence from RANS models group and model one equation of LES models group in simulation are used to investigate the behavior of flow turbulence and the results was compared. In order to adjust the parameters and increase the accuracy of 2D solution, Taguchi design of experiment method was used. To validate the results of blast simulation, the reported laboratory data in the resources have been used. The results show that the explosion simulation in the present study is in relatively good agreement with laboratory data. Then, the effect of barriers on increasing blast wave damping has been investigated.