Study On Slow Cook-off Characteristics Of Fuze And Its Equivalent Components

In order to study the characteristics of the cook-off response of the detonation sequence,and to establish an equivalent model of the fuze,this paper studied the characteristics of the cook-off response of the full fuze through the slow cook-off test.On this basis,two equivalent models of fuze are designed,and the two equivalent models are subjected to a cook-off test.In order to study the influence of the ignition point location on the potential danger of the detonation sequence of the fuze,the numerical simulation of the cook-off of the equivalent component was carried out.At the same time,the influence of the size of the detonator,the physical interface,the heating rate and other factors on the cook-off response characteristics of the equivalent component was studied.The specific research contents are as follows:(1)Using the self-designed cook-off test apparatus,a cook-off test with a heating rate of 3.3℃/h was carried out with the FOX-7 charging and JH-14 charging full fuze,and the thermocouple was used to perform multi-point temperature measurement on the outer wall of the fuze.The test results showed that: When the fuze filled with FOX-7 is cooked-off at a heating rate of 3.3℃/h,the response level of the three parallel test is deflagration;when the fuze filled with JH-14 is cooked-off at a heating rate of 3.3℃/h,the response level of the two parallel test is explosion and partial detonation.The full fuze filled with FOX-7 has better thermal safety than that with JH-14.(2)Two equivalent schemes are designed on the basis of the full fuze cook-off test.The two equivalent components filled with FOX-7 explosives were subjected to a cook-off test with a heating rate of 3.3℃/h.The test results showed that: The response results of the two equivalent components are the same as those of the full fuze,both of which are deflagration reactions.And the fragmentation status is basically the same,indicating that the equivalent scheme of the fuze is feasible.(3)Based on the cook-off test,a cook-off model of two equivalent components was established.The FLUENT software was used to simulate the cook-off of the two equivalent components filled with FOX-7 at a heating rate of 3.3℃/h.The ignition sequence of the equivalent components during the cook-off process was obtained.The ignition mechanism is analyzed by heat transfer theory.On this basis,the numerical simulation of the equivalent component 2 under different heating rates was carried out to study the influence of the heating rate on the results of its cook-off response,and the internal relationship between the heating rate and the ignition position was analyzed.The results show that: When the heating rate is 3.3℃/h,the two equivalent components’ response are the booster ignition happen first,and the ignition point is at the center of the booster.But the heating rate has a great influence on the ignition position of the detonation sequence.With the increase of the heating rate,the ignition position first extends radially from the geometric center of the booster,then migrates to the outermost ring at the bottom of the booster,and finally turns to the geometric center of the detonator,which increases the danger of the fuze and its ammunition under the action of thermal stimulation.(4)Three detonator sizes with the same aspect ratio and different diameters were designed with the model of equivalent component 2,and the critical size of detonator ignition was studied by numerical simulation with the heating rate at which the detonator was first ignited.And the cook-off condition of the heat-insulating physical coating t-09 at the boundary of the detonator was studied under the size of the original detonator.The results show that: The critical heating rate of detonator ignition can be increased by setting the heat insulation layer.When the heating rate is lower than the critical value,the booster can be ignited before the detonator to improve the safety of the fuze in the thermal environment.The above conclusions are of great significance to thermal safety analysis and structural design of fuze and detonation sequence.