Study On The Relationship Between Venting Structure And Explosive Response Intensity Under Thermal Stimulation

In order to study the response characteristics of explosive charges under the venting structure,different venting structures were designed for the grenade fuse with FOX-7 explosive and composition B.Taking the pressure balance at the ignition time of the explosive charge as the condition,the area of the venting hole that only produces the combustion reaction after the grenade fuse filled with FOX-7 explosive and the fired bomb filled with explosive B is calculated,and the fuse and firing are designed.Sustained venting structure for ammunition.First of all,the slow cook-off and fast cook-off tests of the grenade fuse with FOX-7 charge were carried out to verify the effectiveness of the venting structure.The temperature rise rate of slow firing is 3.3K/h,and the test results show that the fuse response level without venting hole is combustion reaction,and when there is venting hole,the fuse response level is reduced to the reaction below combustion;fast firing uses aviation kerosene as fuel.The test results show that the response level of fuses with or without venting holes are all combustion reactions,but the bottom end caps of fuses with pressure relief holes are not completely destroyed by shearing,that is,the bottom end caps of the fuse are more complete than those without venting structure.On the basis of the experiment,numerical simulation is used to study the temperature field distribution inside the fuse.The simulation results show that the ignition point of the fuse is at the center of the booster during slow firing and the ignition point for fast firing is at the bottom of the booster.The FOX-7 explosive itself is an insensitive explosive,so the effect of the slowrelease structure is limited.And for the same structure,the response results of different thermal stimulus intensities are not the same.Subsequently,the slow cook-off and fast cook-off tests were carried out on the cook-off bombs with different venting structures loaded with B explosive.The charge diameter of the sample is ￠35mm,￠76mm and ￠130mm,and thermocouples are designed to monitor the temperature at different positions inside the grain.The test results show that under the condition of slow cook-off,the response level of ￠35 mm ammunition without pressure relief hole and pressure relief hole area is 2.0% is detonation reaction,and when pressure relief hole area is greater than 2.5%,it is combustion reaction;When the area of the pressure relief hole of the 76 mm fire bomb is 2.5%,it is a detonation reaction,and when it is 3.5%,it is a combustion reaction;when the area of the pressure relief hole of a 130 mm fire bomb is greater than 2.5%,it is a combustion reaction.And under the slow cook-off condition,the response points of the test pieces of the melt cast B explosive are all at the top of the grain.Under the conditions of fast cook-off,the response level of ￠76 mm fire bomb without pressure relief hole is detonation reaction,and when the pressure relief hole area is 2.5%,it is combustion reaction;when ￠130mm fire bomb decompression hole area is 2.5%,it is also burning.reaction.It can be seen that the venting structure can effectively reduce the response intensity.In order to further understand the mechanism of the venting structure of melt-cast explosives under different thermal stimulation conditions and the changes in the internal temperature field of the grains,numerical simulations were used to study the results.The results show that under slow-bake conditions,B explosives will melt for a period of time There is a solid phase temperature distribution inside.With the increase of temperature and the effect of the viscous flow field,the internal temperature of the explosive presents a layered distribution,and the larger the diameter of the specimen,the more obvious the layered distribution,and the final ignition point is at the top of the charge.The decomposition reaction of RDX is the main reason that causes B explosive to ignite under slow cook-off conditions;under fast cook-off conditions,only the explosive on the wall is melted at the moment of ignition of the explosive.The internal temperature of the charge is very low,and the temperature gradient is large.It is caused by explosive reaction in a high temperature area.The above research conclusions have important reference value and guidance for the thermal safety of the charge and the design of the venting structure of the ammunition.