فهرست مطالب s. tavangar

Porous explosives such as octogen (HMX) are classified as high-sensitivity secondary explosives, which are in powder form and are usually charged by the pressing method. Investigating the behavior of these materials under shock waves has always been a challenge for researchers. In this research, the hydrodynamic behavior of these materials in the shock tube was investigated in a two-phase manner. In the modeling of two-phase systems with the presence of shock waves, the differential equations are hyperbolic; Therefore, to capture the pressure pulse in the shock tube, a Riemann solver is needed. In this research, Ecogen software was used for simulation. This software is equipped with Kapila's multiphase model and uses a Riemann solver with the ability to capture shock waves to solve differential equations. Simulation of the shock tube in two modes of pressure pulse with low amplitude and pressure pulse with high amplitude was carried out using two-phase Kapila model and data from previous researches were used for validation. Comparing the results of the simulation with the data of previous researchers showed a difference of less than 5%.

Surface coating is the most common method to reduce the sensitivity of energetic materials. The efficiency of this technique depends on the preparation method and the coating agents. This process is carried out through different methods. In order to reduce the sensitivity of HMX particles, waxes are conventionally used, which leads to decrease in HMX energy content. In this research, using three energetic compounds NC, DINA and TNT, the solvent/anti-solvent method was used for HMX coating. The scanning electron microscopy (SEM) was utilized to investigate the morphology. The results showed that uniform samples with optimal coverage are composed of coating agents. The Fourier-transform infrared (FT-IR) spectra confirmed the surface interaction between the HMX and coating agents. The thermal behavior of the coated samples was investigated by simultaneous thermogravimetric and differential scanning calorimetry analysis (TG-DSC). Results showed that while maintaining the thermal stability of coated HMX in respect to pure HMX, the heat of reaction from 1569.29 J/g for pure HMX increased to 1612.88, 1707.01, and 1690.38 J/g equivalent to 2.8%, 8.8% and 7.7% for coated samples with NC, DINA and TNT, respectively. Additionally, in the case of the HMX/TNT, the impact sensitivity of the 1 kg sample is reduced compared to the pure HMX, and for HMX/NC and HMX/DINA, no significant change was observed.

Unsaturated polyesters have several applications in organic chemistry such as click reaction, radical reaction, etc. In this research, in the first step, a new and inert type of unsaturated binder containing internal alkyne groups was synthesized. For this purpose, condensation polymerization of 2-butyne-1,‌4-diol, and DL-malic acid was performed at 130 °‌C without solvent. Thermal properties were studied by DSC and TGA analyses. All synthesized structures were confirmed by 1H NMR, 13C NMR, FT-IR, and GPC analyses. The synthesized poly (2-butyne-1,4-diol-co-malic acid) can be used as a binder and contains internal alkyne groups with a molecular weight is 1818 g.mol-1 and its polydispersity index of 1.75. According to the DSC study, the glass transition temperature of poly (2-butyne-1,4-diol-co-malic acid) was -38 °C, and its degradation temperature was 299 °C. Then, crosslinking and curing of poly (2-butyne-1,4-diol-co-malic acid) with glycidyl azide polymer was performed at 60 °C for 72 hours, and the tensile strength was obtained 5.63 MPa.

In the current research work, a zero-dimensional code for the internal ballistic of gun analysis has been developed with a deterrent layer propellant. Today, the driving of the deterrent layer is widely used in small and medium-caliber weapons. The deterrent layer is in the form of a thin coating on the surface of a single base or double base gun propellants. The main purpose of this type of propellants is to increase the muzzle velocity by observing the maximum allowable pressure for the weapon. It has been developed for internal ballistic analysis of the thermodynamic model or the next zero-based on Badr software relations. In order to validate the analysis results, experimental results and results of other valid codes related to 20 mm weapon and 30 mm laboratory weapons were used. The code is able to analyze the combustion of two-layers propellants with a variety of conventional geometries for a grain. The effect of the engraving force on the accuracy of the examined results and the impact of deterrent layer on internal ballistic of gun performance has been discussed. The results show that in case of using the deterrent layer with increasing the load density can be reach to higher muzzle velocities with maintaining maximum allowable pressure. The investigation on M55A2 ammunition demonstrated 9.5% increasing in muzzle velocity by using of deterred propellants rather than undeterred propellants.

When dealing with research and development of the gun propellants, a less expensive, quicker and safer process of the closed vessel evaluation adopted can be used rather than the gun firing test. In the current research work, a computer program (BRCBADR) has been developed for in order to obtain the burning rate reduction coefficients from the closed vessel test data. Correct The correct determination of the thermo-chemical properties of the propellants provides accurate results of interior ballistics analysis. The BRCBADR code has been developed based on a zero dimensional model for evaluating pressure history of burning propellants in a the closed chamber. A new curve fitting method based on the shooting Shooting algorithm is used to calculate burning rate coefficients. In this program, the experimental values of impetus and co-volume have determined from the Noble-Able equation of state. The results of present code are in well agreed agreement with the results of other validated codes. Using of burning rate calculation method has resulted in accurate muzzle velocity prediction (less than one percent error) from 122 mm gun firing. The results of This this research showed that,exhibited the regardless of slivering effects during the burning of seven perforated cylindrical grains, while resulted tothe additional unreal impulse is applied to the projectile.