Research On Contact Impact Dynamic Characteristics And Structural Optimization Of Artillery Extractor System

During the shooting process of automatic and semi-automatic artillery,the task of extracting the cartridge is accomplished by the extractor system.According to the statistic data of unit training and the Sino-Vietnamese War and the existing literature,there are mainly two kinds of malfunctions of the extractor system.One is the cartridge being broken under the extracting force applied by the extractor and the resistance applied by the ballistic pressure.Thus the cartridge cannot be completely extracted.The other is the plastic deformation and dynamic fracture of the functional components,resulting in failing extracting.The malfunctions of the extractor will lead to the guns stopping working,it cannot give full play to its fighting capacity.Aiming at the problems of cartridge jamming,plastic deformation or fracture of components of the extractor system,the presented paper studies the extractor system of a vertical wedge breech.Based on the kinetic theory and the virtual prototype technology,the contact dynamic characteristics during the extracting process is analyzed.And the extractor is designed by using the topology optimization approach,Firstly,the extractor system of the vertical wedge breech is modeled.Then the working mechanism of the extracting process is described.By using the static elastic-plastic theory and the nonlinear FEA method,the extracting process is analyzed.The threshold pressure when the cartridge will not be snapped is derived,and the proper extracting time is determined.By assigning the movement of the cartridge,the extracting resistance is obtained,which is also the working resistance of the dynamic response of the extractor system.Secondly,to extracting the cartridge in assigned movement successfully,the continuous contact kinetic model of the extractor system is established.The movement of each component is derived.And the impact and extracting force is obtained,which will be applied to analyzed the structural strength of the component.Thirdly,the elastic wave equation of the extractor,which is simplified into a plate with hole,is established.By using the finite difference time domain method,numerical calculation of the equation is carried out.The dynamic stress distribution and region of stress concentration during the extracting process is derived.Furthermore,the influence on the stress amplitude and fluctuation attributing to the change in mechanical parameters,including the elasticity modulus,the Poisson's ratio and the density,and the impact velocity is analyzed.Finally,dynamic Finite Element Analysis of the extractor is carried out,and the equivalent stress distribution of the extractor is obtained.Combining with the theoretical results,the stress concentration region is determined further.By using the topology optimization method,the optimal design of the extractor is carried out.Based on the obtained optimal material distribution,the extractor is redesigned and the FEA of the new structure is carried out.And the optimized extractor shows better mechanical property,which provide a reasonable and effective approach to avoid extracting malfunction.This paper provides theoretical foundation for resolving the problem of extracting malfunction and paves the way for the dynamics optimization and dynamic strength design of the extractor system.