Experimental Investigation on Shock Wave Characteristics of Aluminized Explosives in Air Blast

To investigate the shock wave characteristics of RDX-based aluminized explosives,air blast tests were conducted for measuring the parameters of 10 kg aluminized explosives which contained 0-40% aluminum.The results showed that with the increasing of aluminum content,the overpressures and impulses increase at first and then decrease within 7 m or 5 m,which reached the maximum when aluminum content was 20% or 30%.Power exponential formulas are used to fit the shock wave parameters vs scaled distance,where an equal weight of TNT is used to calculate the scaled distance.The overpressures of HL0 and TNT in tested locations not only conform to the similar law,but also conform to the same attenuation law after gaining the scaled distances of equal TNT mass.The pre-exponential factors of overpressure and impulse,kp and kI,decrease along with the increasing of Al content and keep the same pace as the calculated PCJ）.The attenuation coefficients a_P and aIincrease at first and decrease later with the increasing of aluminum content,and they reached the maximal values with30% Al containing,which keeps the same pace as the calculated QV.

Optimization of the Air Deck Blasting Parameters on the Basis of the Holmquist-Johnson-Cook Constitutive Model

The present study considers the so-called air deck blasting,one of the most commonly used techniques for the improvement of blasting efficiency in mining applications.In particular,it aims to improve the operating conditions of large-scale equipment,increase the efficiency of the slope enlarging process,and reduce the mining cost.These objectives are implemented through a two-fold approach where,first,a program for slope enlarging based on the middle air-deck charge blasting-loosening technology is proposed,and second,the physical mechanism responsible for the stress wave attenuation in the rock is analyzed in the framework of a Holmquist–Johnson–Cook constitutive model.Field test results verify that the proposed approach is highly efficient and economical when used in medium-hard rock blasting and thus provides a basis for the practical implementation of slope enlargement for high benches in Open-Pit Mines.

Effects of content and particle size of TiH2 powders on the energy output rules of RDX composite explosives

In order to improve the detonation characteristics of RDX,a RDX-based composite explosive with TiH_(2)powders was prepared.The effects of content and particle size of TiH_(2)powders on thermal safety,shock wave parameters and thermal damage effects of RDX-based composite explosive were studied with the C80 microcalorimeter,air blast experiment system and colorimetric thermometry method.Experimental results showed that TiH_(2)powders could enhance the thermal stability of RDX-based composite explosive and increase its ultimate decomposition heat.The content and particle size of TiH_(2)powders also had significant effects on the thermal safety,detonation velocity,shock wave parameters,fireball temperature and duration of RDX-based composite explosives.Furthermore,the differences of TiH_(2)and Ti powders on the detonation energy output rules of RDX-based composite explosives were also compared,showing that TiH_(2)powders had better influences on improving the explosion power and thermal damage effect of RDX-based composite explosives than Ti powders,for the participation of free H_(2)released by TiH_(2)powders in the detonation process.TiH_(2)powders have important research values as a novel energetic additive in the field of military composite explosives.

Particle Swarm Approach for Structural Optimization of Battleship Strength Deck Under Air Blast

This paper presents the implementation and application of a modified particle swarm optimization(PSO) method with dynamic adaption for optimum design of a battleship strength deck subjected to non-contact explosion. The numerical simulation process is modified to be more computationally efficient so that the task is realizable. The input variables are the thickness of plates and the dimensions of stiffeners, and the total structural mass is chosen as the fitness value. In another case, the response surface method(RSM) is introduced and combined with PSO(PSO-RSM), and the results are compared with those obtained by the traditional PSO approach. It is indicated that the PSO method can be well applied in the optimum design of explosion-loaded deck structures and the PSO-RSM methodology can rapidly yield optimum designs with sufficient accuracy.

Theoretical modeling and numerical simulations of plasmas generated by shock waves

Electromagnetic(EM) field is a consequence of the plasma generation induced by shock waves generated in impacts and explosions and is an important topic of study in aerospace and geophysics. Experimental research is frequently used to investigate the plasma generation in hypervelocity impacts and the EM wave emitted in chemical explosions. However, the basic plasma generation mechanism leading to the EM emission generated by the shock waves in chemical explosions is rarely studied.Therefore, a detailed investigation is performed to determine the state of the plasmas generated by the shock waves in air blast. In addition, a multi-component ionization model was improved to evaluate the ionization state of the generated plasmas. The proposed ionization model was combined with an AUSM+-up based finite volume method(FVM) to simulate the plasmas generated in the air blast. Two typical cases of simulation were carried out to investigate the relation between the shock waves and ionization, as well as the influence of ground reflection on the ionization state. It was found that the ionization zone was close behind the shock front in the air and propagates along with the shock waves. The interaction between the original shock waves and reflected shock waves was found to have a great impact of the order of 2–3 magnitudes, on the degree of ionization of the plasmas generated by the shock waves. This phenomenon explains the observation of additional EM pulses generated by ground reflection, as explored in the reference cited in this paper.

Influence of energy removal rate on the quality of minced meat from undersized crawfish during frozen storage

Undersized crawfish have little economic value and are often discarded.Producing crawfish minced meat(CMM)from undersized crawfish and using an appropriate freezing technique may enable an economically viable market.The objective of this research was to evaluate the effect of the energy removal rate using two techniques,cryogenic freezing(CF)and air blast freezing(BF),on CMM’s quality during frozen storage.CMM was separated into two batches;one batch was cryogenically frozen with liquid nitrogen and the other batch was frozen with an air blast freezer.CMM batches were frozen and stored at−18℃.They were analyzed for moisture content,color,pH,and lipid oxidation during 180 days of storage.The CMM yield was 64.67%of the total crawfish weight.Cryogenic freezing achieved the highest freezing rate.Cryogenically frozen CMM showed 22%less lipid oxidation than CMM frozen by air blast freezing at 180 days of storage.This study showed that CMM could be mechanically produced from undersized crawfish and freezing techniques with high energy removal rate could better maintain quality attributes for CMM during frozen storage.