Research On Ballistic Explosion Of Rifled Artillery Fuzes

A certain 76 mm caliber high explosive projectile had two ballistics burst accidents during live-firing.The direct cause of the accident was that the inertial firing mechanism inside the fuze acted in advance.And other types of fuzes equipped with the inertial firing mechanism also had ballistic burst accidents.In order to explore the root cause of the ballistic burst of the rifled gun fuze with the inertial firing mechanism,based on the fault tree analysis method,the probability of fuze ballistic burst was estimated,the distribution law of projectile structural parameters and the correlation between structural parameters and dynamic unbalance angle were studied,and the ballistic safety of inertial firing mechanism was analyzed.The main research results of this paper are as follows:In order to estimate the probability of fuze ballistic burst,the fault tree analysis method is proposed to analyze the fuze ballistic burst.Based on the bottom event and its numerical range of fuze fault tree in national military standard,the bottom event of fuze ballistic burst and its numerical range are established,and the probability of fuze ballistic burst is estimated to be 10^-5?10^-4.Based on the fault tree analysis method,the ballistic burst probability of the mechanically triggered fuze of the 76 mm caliber high explosive is estimated.The estimated result shows that the ballistic burst probability of the fuze is 3.2×10^-5?4.32×10^-5 under normal conditions.In live-firing,the probability of the fuze's ballistic burst is far beyond the above-mentioned value.Therefore,it is judged that the fuze may have some problems,such as the fuze may have defects in design principles,the ballistic environment analysis is inadequate,the process defects,the batch of raw materials,explosive components and electronic components are unqualified,or the fuze and ammunition are not suitable.To help study the distribution of projectile structure parameters,based on Monte Carlo method and basic element method,the mass,eccentricity,polar moment of inertia,equatorial moment of inertia,dynamic unbalance angle and the ratio of polar moment of inertia to equatorial moment of inertia of a 76 mm caliber high explosive projectile were calculated through numerical simulation.The simulation results are estimated by maximum likelihood,this result is approximately consistent with the results of the measured projectile's structural parameters,which indicates that the calculation results of the above method are feasible,and the above simulation results can be used to analyze and calculate the fuze ballistic burst.In order to study the correlation between some structural parameters of the projectile and the dynamic unbalance angle of the projectile,the structural parameters of 50 projectiles were measured.Based on the Levenberg-Marquardt method and the general global optimization algorithm,the 1st Opt software was used to analyze the correlation between the mass,eccentricity,centroid position,polar moment of inertia,equatorial moment of inertia,the ratio of polar moment of inertia and equatorial moment of inertia of the projectile with the projectile dynamic unbalance angle.The research results show that the projectile eccentricity,mass,and the ratio of the polar moment of inertia and the equatorial moment of inertia have a larger correlation with the projectile dynamic unbalance angle,and the correlation between the other structural parameters and the projectile dynamic unbalance angle is weak.Therefore,when it is impossible or difficult to measure the projectile dynamic unbalance angle,the projectile dynamic unbalance angle can be estimated by measuring the projectile mass and eccentricity and combining the Monte Carlo simulation results.In order to find out the reason why the inertial firing mechanism works abnormally on the exterior trajectory,starting from the working principle of the inertial firing mechanism of the US military M739A1 mechanical trigger fuze,considering the motion around the center of the projectile(nutation,precession and rotation),the eccentricity of the movable body in the self-adjustment delay mechanism,the radial eccentricity between the mass center of the movable body and the mass center of the projectile,the dynamic unbalance angle of the projectile,and the assembly angle between the projectile and the dynamic friction between the movable body and the shell in the self-adjustment delay mechanism,the force of the movable body is studied.Based on the above analysis results,the kinematics equation of the movable body is established.Based on certain assumptions and analysis,a movable body movement model which is convenient for engineering application is obtained.The 76 mm caliber high explosive projectile is used as an example to verify the correctness of the above model.And through analysis,it can be known that the key factor that causes the ballistic burst of the fuze is:the assembly angle between the projectile and the fuze is too large,and the secondary factors include:the resistance of the movable body spring in the inertial firing mechanism is too small,the projectile dynamic unbalance angle is too large,the radial eccentricity of the living body is too large and too large nutation angle,etc.In response to the above analysis results,several quick measures are proposed to effectively improve the ballistic safety of the76 mm caliber anti-explosive projectile.