Refined Modeling Of Interior Ballistics And Its Application In The Study Of Erosion And Wear In Gun Bores

Wear and erosion of gun bores under high-temperature and high-pressure propellant gases are unavoidable.To investigate the wear and erosion,interior ballistic loads that determine the wear and erosion should be thoghouly studied.Refined mathematical models and high precision numerical methods are very important for numerically predicting the interior ballistic loads.However,due to the high-temperature and high-pressure propellant gases in the chamber and the non-linear mechanical interactions between the projectile and the barrel,most of the current mathematical models and numerical methods are established based on many simplifications.Based on previous works on interior ballistics,the following key probloms are investigated in detail for establishing the refined mathematical models and numerical methods for interior ballistic problems.The first one is the mechanical interactions between the projectile and the barrel,in which the engraving process of rotating bands is considered.The second key problem is the coupling between the combustion of propellants and the mechanical interactions.The third key problem is the coupling between the transient heat conduction in the barrel and the propellant combustion in the chamber,in which the heat losses of the propellant gasses are compensated.The last one is the coupling between wear and erosion of gun bores and interior ballistic processes.Based on the detailed studies of the key problems,refined mathematical models and numerical solution frameworks are constructed for the combustion of propellants during interior ballistic processes.The mathematical models and numerical methods can provide theoretical and practical support for the research on interior ballistics,charge designs and use of guns.The details are as follows:a)Mechanical interactions between the projectile and the barrel.The finite element method(FEM),the finite element-smooth particle flow coupling method(FEM-SPH)and the EulerLagrange coupled method(CEL)are utilized to analyze the dynamic solid mechanics problems involving contacts,collisions and material damages.Based on the methods,the engraving processes of projectiles are studied.The effects of different methods in simulating the engraving processes are discussed.The study of the key problem provides reliable numerical methods predicting the non-linear structural responses for the coupled calculation of the interior ballistic processes and the mechanical interactions in the subsequent works.b)Coupled calculation between the classical interior ballistic model and the mechanical interactions between the projectile and the barrel.To eliminate the assumptions used to simplify the interactions between the projectile and the barrel,the energy conversion process of the charged propellant in the barrel is analyzed and a modified energy equation is constructed for classical interior ballistic model.A computational framework is established for coupling the combustion of propellant and the mechanical interactions.Based on the framework,the influences of structural parameters on interior ballistics are analyzed.c)Coupled calculation between two-phase interior ballistic model and the mechanical interactions.To deal with the high-pressure and high-temperature environment,transient effects,moving boundaries,diccontinuities such as shock waves and flame waves in the fluid field,a coupled numerical model based on Godunov scheme is established to predict the two-phase reactive flows in the barrel.Based on the coupled model,the influences of the distributed pressure acting on the inner surfaces of the barrel on the mehacnical interactions and the interior ballistics are analyzed.The results indicate that the influences of the distributed pressure can not be ignored when investigating interior ballistic problems.d)Coupled calculation between the transient heat transfer in the barrel and the interior ballistic processes.To deal with the simplified heat losses of the propellant gases used in interior ballistic theory,the basic equation in the classical interior ballistic model and the energy equation of the gas phase in the two-phase reactive flow model are modified.Two real-time bidirectional coupling models for predicting the propellant combustiuon and the transient heat conductionin the barrel are established.Based on the coupled models,the interactions between the transient heat conduction and interior ballistic process are analyzed.The results show that two-phase reactive flow model performs better than the classical ballistic model in giving convective boundary conditions during the initial stage of interior ballistic process and the region near the forcing cone of the barrel.e)Coupled calculation between wear and erosion of the barrel and the propellant combustion.Based on the coupled computational framework,the influences of the unavoidable wear and erosion on the performances of interior ballistics are investigated.According to the results,two kinds of methods are provided to maintain the performance of interior ballistics for the barrel in different life stages.To investigate the peroformances of interior ballistic processes of a gun in different life stages based on the refined coupling model,which simultaneously considers the thermo-mechanical behaviors and the propellant combustion,a novel method is put forward to accelerate the numerical research on the performance variation of interior ballistics along with the accumulating of fired projectiles.Finally,the influences of firing frequency and the distributed pressure acting on the inner walls of the barrel on wear and erosion are disccused.