| Explosive is a kind of material with high energy density,which is widely used in military field and civil engineering.Explosives explode under condition,so as to realize the use value.The effect of explosive explosion is closely related to the gas pressure environment in which the explosion occurs.Negative pressure is a pressure state below one standard atmospheric pressure.In high altitude,high altitude and even space environment,the damage evaluation of explosives is directly related to the efficiency of explosives utilization.How strong is the explosive in thin air or even a vacuum? How or if shock wave propagation is present? These problems are closely related to the damage assessment of plateau blasting and military weapons as well as the possibility of space mining in the future.Explosive processing technology takes explosive as energy source.Will the negative pressure environment improve the explosive energy utilization rate during explosive processing,that is,will the useless shock wave,explosion vibration and noise energy decrease,while the energy of explosion work increase? In addition,does the negative pressure environment play a role in vibration and noise reduction during explosive explosion? It can be seen from a series of problems that it is of great academic and practical significance to study the characteristics of explosive shock wave and explosive vibration and noise under negative pressure environment,which can enrich the explosive theory and provide theoretical support for guiding the military and engineering blasting practice.In order to analyze the explosive characteristics in negative pressure environment,the explosion experiments were carried out in the self-developed 34.8L cylindrical explosive vessel with adjustable vacuum degree and the spherical explosive vessel with 5kg TNT equivalent vacuuming transformation under different negative pressure environment and different dosage.The characteristic parameters of shock wave,wall vibration,ground vibration and explosion noise are measured by pressure sensor,vibration and noise tester.The results show that :(1)negative pressure environment can weaken the intensity of blast wave.The peak overpressure of shock wave decreases with the decrease of negative pressure in explosion environment.(2)The velocity of the blast wave is related to the density of the propagation medium.The lower the environmental negative pressure is,the thinner the gas is and the faster the shock wave propagates.In vacuum environment,explosive shock wave intensity is weak and attenuation is rapid.(3)In the spherical tank experiment,the peak values of experimental overpressure under different negative pressure environments are greater than the values calculated according to Sadowski formula.However,the two deviations are reasonable and the consistency is good.(4)With the same contrast distance,with the decrease of environmental negative pressure,the positive pressure action time of shock wave is not different,but the specific impulse decreases uniformly;(5)The negative pressure environment can attenuate the vibration of container wall caused by explosive explosion.HHT analysis shows that the higher the vacuum degree is,the stronger the vibration attenuation is.The negative pressure environment can reduce the explosion noise,the higher the vacuum degree,the stronger the noise attenuation;(6)For the experiment in the spherical tank,when the charge volume was100 g and 150 g,the vibration intensity of the ground measuring points outside the spherical tank showed a "mountain shape" change with the decrease of the environmental negative pressure,which was low at both ends and high in the middle.When the amount of charge increases to 200 g and 300 g,the vibration peak velocity of ground measurement points increases with the decrease of environmental negative pressure.The peak vibration velocity of ground measurement point is affected by shock wave intensity and pressure difference constraint.Finite element software auto-dyn was used to simulate the propagation process of explosive shock wave under negative pressure environment.The results show that :(1)with the decrease of negative pressure,the overpressure of shock wave decreases,the specific impulse decreases,the wave velocity increases,and the time of positive pressure does not change much.(2)In the same negative pressure environment and at the same monitoring point,with the increase of drug dosage(the comparison distance becomes smaller),the shock wave overpressure increases,the specific impulse increases,and the positive pressure action time changes little;(3)In the same negative pressure environment,the dose remains unchanged.With the increase of the distance from the explosion center at the monitoring point(the contrast distance becomes larger),the shock wave overpressure becomes smaller,the specific impulse rises first and then decreases,and the positive pressure action time becomes larger;(4)The deviation between simulated overpressure value and the value calculated by Sadowski formula is 0.65%-5.37%,and the two values are close to each other.The simulated shock wave parameter results are basically consistent with the experimental results in the spherical tank,but because the experimental environment cannot achieve a completely free field,the overpressure deviation of the simulated value relative to the experimental value is 10.23%-19.85%,the positive pressure time deviation is less than5.78%,and the specific impulse deviation is-12.80%-6.89%.Therefore,the simulation results are in good agreement with the experimental results.The results show that :(1)through metallographic microscopic observation,the bonding surface of copper-steel composite plate under negative pressure is uniform,tensile and compression strength is high,but the plasticity is reduced.(2)By scanning electron microscope observation,the effective bubbles of chemical sensitized emulsion explosive are relatively reduced under negative pressure,and the phenomenon of explosion rejection may occur in practical engineering;(3)Under experimental conditions,the detonation velocity and abruptness of emulsified explosive measured in negative pressure environment increased compared with atmospheric pressure environment,the growth rate of detonation velocity was 2.49% ～ 6.57%,and the growth rate of intensity was-0.41% ～ 19.78%.Figure [81] Table [44] Reference [144]... |
PDF Full Text Request