The Study On The Dynamic Of The Projectile-barrel Coupled System And The Corresponding Key Parameters

The projectile,which is acted by high-temperature and high-pressure propellant gas during the firing process of artillery,moves along the barrel axis at high-speed velocity.Due to the existence of barrel bend,the contact-impact between the projectile and bore,rotation band deformation,and high speed friction between the rotation band and bore etc.,the projectile moves with uncertainty,resulting in the disturbance of the state parameters of the projectile at muzzle,which is the initial conditions of the exterior directly related to the firing accuracy of the artillery.Therefore,it is of great importance for improving the firing accuracy of artillery to establish the projectile-barrel coupled system dynamics model,obtain the rule of movement of the projectile in the barrel,reveal the coupled relation of projectile and barrel,predict the disturbance of state parameter of projectile at muzzle,extract the key parameters which have great influence on the state parameters of projectile at muzzle.To solve these problem above,the main research contents and results are as follows:(1)The relative movement of coordinates in the projectile-barrel coupled system is established on the basis of the artillery firing principle and physical structures.Through the topological structure of the system,the kinematic equations are established by the movement description of adjacent rigid bodies.Combined with the system kinematic equation,the dynamical equations are established on the basis of virtual power.(2)Considering the rigid-flexible coupling effects of the barrel and on the basis of Timoshenko beam theory,the barrel model is established by multi-barrel beam model.The discrete barrel model is built by using the spectral element method and the dynamic equation of flexible barrel is obtained.The dynamic equation is established based on the Timoshenko beam theory through floating frame method.(3)The problems of projectile-barrel coupled system are analyzed comprehensively and systematicly,which include the interaction of rifling and rotating band,the effects of the projectile movement on the movement of barrel,the contact-impact events between the front and back projectile and bore,the deformation of rotating band,the high speed friction between rotation band and bore.The corresponding constraints equations are established,which are integraed into the system dynamical equations.(4)The dynamic equations of projectile-barrel coupled system considing the effect the rigid flexible coupling and projectile-barrel coupling,and the corresponding algorithm are provided.The projectile-barrel coupled system is analyzed during the process of fire,including the load acted on projectile and barrel.The simulation which is conducted in this part includes 1)the muzzle disturbance results are compared with the experimental ones to verify the effectiveness of the model;2)the static analysis is carried out which is the initial condition of dynamic analysis;3)the simulation of the system is carried out by using the initial conditions above,the results show that the movement of the projectile displays a clear cyclicity and the amplitude of the lateral movements becomes larger and reaches a maximum value in the vicinity of the muzzle with the movment of the projectile.(5)The ASPCE metamodel model technology is proposed based on the principle of PCE.Sobol' global sensitivity factor can be obtained from the ASPCE coefficient on the basis of Sobol' global sensitivity analysis.Combing with the barrel natural frequency model,the ASPCE metamodel model is established to obtain the sensitivity factor of the key parameters.The results show that there are 5 key parameters affecting the natural frequency of barrel,namely,the mass of muzzle brake Mk,the outer diameter of back surface of barrel D4,the first outer diameter of barrel D3,the second outer diameter of barrel D2,the outer diameter of front surface of barrel D1.(6)The Minimax distance criterion is adopted to improve the Quasi-OTEE global sensitivity analysis method.Combined with the projectile-barrel coupled system dynamic model,the key parameters are chosen by considering a comprehensive system input parameters and conducting a global sensitivity analysis,which provides reference for subsequent detailed analysis.The results of calculation show that there are 8 important key parameters of projectile affecting the projectile muzzle state:the vertical position of projectile centroid,the lateral position of projectile centroid,the portrait position of front centering portion,the mass of projectile,the equatorial moment of inertia of projectile Iyy and Izz,the width of front rotation band,the width of back rotation band.There are 8 important key parameters of barrel affecting the projectile muzzle state:the mass of muzzle brake,the first outer diameter of barrel,the second outer diameter of barrel,the outer diameter of front surface of barrel,the vertical velocity of projectile after engraving process,the lateral velocity of projectile after engraving process,the vertical angular velocity of projectile after engraving process and the lateral angular velocity of projectile after engraving process.There are 4 important key parameters of the couple of projectile and barrel affecting the projectile muzzle state:equivalent stiffness of rotating band,the steel-steel contact stiffness and gap between the projectile and the barrel,and the clearance between the barrel and cradle.In addition,the results show the parameters are same affecting the projectile muzzle state and the barrel natural frequency.