Study On The Frictional Response Characteristics Of The Pressed Explosives

The explosive can generate a rapid and fierce chemical reaction under external friction stimulus,and release a lot of energy in a short period of time,leading to the failure of the weapon system or the destruction of the surrounding medium.In the process of friction ignition,there are many factors influencing the temperature rise of explosives,including friction coefficient,interface normal pressure,heat conduction coefficient and melting point of friction pair,interface inhomogeneity and hard impurity particles,etc.In addition,the chemical factors like the activation energy and the reaction heat of the explosive will also have an effect on the ignition of the explosive during the friction,which means the friction ignition of explosives is a thermal-mechanical-chemical coupling problem.Therefore,it is difficult to theoretically study the friction and heat generation of explosives,and the experimental analysis and numerical simulation have become the main research approaches.Furthermore,according to the classical phenomenological theory,the sliding friction force is the product of the coefficient of dynamic friction and the normal force of the interface.Therefore,the most important factor in the general friction heat calculation is the dyanmic friction coefficient between the interfaces.To sum up,the study of influence factors of the friction coefficient of explosive is very important to analyze the stability of explosive in the process of friction.In this paper,a self-designed friction test system based on the drop hammer apparatus is used to carry out the experimental study on the pressed explosives 8701.The skid friction experiment of 8701 explosives is analyzed with LS-DYNA numerical simulation.The main contents are as follows:Firstly,the test device of the dynamic friction coefficient of the pressed explosive,including the drop hammer velocity loading system,the explosive pressurization system and the signal test system,is independently designed.The device can test the dynamic friction coefficient of the pressed explosive under high-speed and high-pressure conditions,and truly reflect the friction response process,and can be used to carry out experimental research on the factors affecting the friction coefficient of the pressed explosive.Secondly,the dynamic friction coefficient of 8701 pressed explosive is studied using the test system.The experimental results show that,under high-speed and high-pressure loading conditions,the experimental device can maintain the integrity of the pressed explosive.As the normal pressure of the friction interface is increasing,the friction coefficient between the explosive and the stainless steel will gradually decrease.When the normal pressure exceeds 10 MPa,the change in friction coefficient is very small and tends to be stable.Finally,according to the experimental results of the sliding friction experiment of 8701 pressed explosive,a formula for calculating the dynamic friction coefficient of 8701 explosive is proposed,and the calculation model of friction coefficient in LS-DYNA is modified,and the stability of 8701 explosive in skid test is analyzed.The results show that in the modified friction coefficient calculation model,the ignition delay time of the explosive is prolonged,the critical ignition speed and critical ignition temperature are increased.This indicates that the calculation model of friction coefficient modified with pressure correlation is of great significance for the study of the friction ignition of the pressed charge explosives.In summary,the friction test system designed in this paper can provide reliable experimental support for the investigation of the friction ignition response of the pressed explosive,the numerical simulation method can be used to analyze the temperature rise of pressed explosive.The present work is beneficial to the comprehensive evaluation of the friction ignition response of the other explosives.