Research On The Dynamic Characteristics Of The De-rotation Process In The Chamber Of The Sliding Plastic Belt-guided Projectile

The despinning of guided projectile with slipping plastic driving band in barrels is essential to the safety and damage performance of the projectile.The process of guided projectile with slipping plastic driving band despinning is an extremely complex process with non-linearity,high transient,strong load,large deformation and damage failure etc.Its essential effect cannot be described clearly by the analytic model of classical theory.It is difficult to meet the requirements of the development of modern artillery,so it is necessary to study the dynamic characteristics of the spin reduction process in the bore of the sliding plastic belt guided gun.In this dissertation,the process of guided projectile with slipping plastic driving band despinning was taken as research project.A constitutive model which can describe the mechanical behavior of the plastic driving band at different strain rate was constructed based on the combination experimental and the theoretical analyses.The constitutive model of the plastic driving band was incorporated into ABAQUS through the user-defined subroutine(VUMAT)with Fortran code and applied to the finite element analysis model of the despinning of guided projectile with slipping plastic driving band in barrels.The influence of the structural parameters of the slipping plastic driving band on the process were obtained.The following works were accomplished:(1)Experimental study on the mechanical properties of plastic band materials.Tensile,compression,combine compression and shear and SHPB tests were performed on the nylon plastic band under various strain rates by using the universal testing machine and Hopkinson pressure bar.The elastic modulus,yield strength and other parameters of plastic band material are obtained by the test results.The test results show that the mechanical behavior of the plastic elastic band material has obvious strain rate sensitivity,and its yield strength increases with the increase of the strain rate.(2)Constructing the material constitutive model of nylon and the user-defined subroutine.On the basis of the yield model proposed by Farrokh,a constitutive model which can describe the mechanical behavior of nylon plastic band materials at different strain rates was constructed by introduced a non-linear isotropic hardening model and the plastic internal variable represented by cumulative equivalent plastic strain.The material parameters in the constitutive model were fitted according to the test results.The constitutive model was written into VUMAT by using Fortran language adopting a stress compensation updating algorithm based on elastic tensor and applied to the analysis model of finite element examples.The tensile and compression mechanical responses of material samples under different strain rates are numerically simulated.The capability of the developed constitutive model was examined by the comparison with the experimental results.The results show that the mechanical behavior of plastic band material has obvious strain rate sensitivity,and its yield strength increases with the increase of strain rate.(3)The physical and mechanical analysis of the despinning of guided projectile with slipping plastic driving band in barrels were conducted.The force in the process of guided projectile with slipping plastic driving band despinning was presented based on the classic theoretical model.The two forms of action of the sliding plastic band structure and the band groove are summarized.The second equations of the rotational speed of the sliding plastic band and the guided projectile,which provides the theoretical basis for the analysis of the despinning of guided projectile with slipping plastic driving band in barrels,are given.(4)The numerical simulation method was used to study on the process of guided projectile with slipping plastic driving band despinning in barrel.The finite element analysis model of the process of guided projectile with slipping plastic driving band despinning was established by ABAQUS and VUMAT,and the nonlinear simulate was performed.The dynamic response of the process was obtained.The formation process of the rotating band grooves was analyzed,and the dynamic response of the guided projectile body in barrels was clarified.The rotation speed curves of the plastic band and the guided projectile body in barrels were obtained,and the low of the rotating speed in barrels was exposed.The law of three factors,different coefficient of friction between the sliding plastic band structure and the band groove,different width of the band and the different radial force quantity of band,on the process were studied by comparing the dynamic response and characteristics.In this paper,mechanical tests and a constitutive model of plastic band were carried out,and numerical simulation analysis of the process of guided projectile with slipping plastic driving band despinning were investigated.This study would be further used for design and analysis of the launching process in barrels of the guided projectile with slipping plastic driving band.