Structural Response Of Non-normal Penetrating Projectile Under Reverse Impact

The transient structural response of high-speed kinetic projectile is a hot and difficult problem in this research field.Obtaining the real-time dynamic response and establishing the response rule under different projectile-target conditions have a great significance to understand penetration dynamics and engineering design.In this dissertation,based on Digital Image Correlation(DIC)technology,the forward/reverse ballistic impact experiments of solid/hollow Taylor rod,the transverse/oblique impact experiments of free-free beam and the non-normal penetration experiments of structural projectiles were performed,the real-time dynamic structural responses were measured and the equivalent condition of forward/reverse ballistic is proposed and validated.The traditional free-free beam theory has been improved,and a theoretical model to calculate the projectile response has been derived considering the interactions between axial and lateral loads.The double-ogive nose projectile with smaller penetration resistance and better structure stability has been designed which is practical in engineering.The main work and conclusion are as follows:(1)The influence of mass ratio on the Taylor reverse impact was analyzed at the energy point,and the equivalent condition of structural deformation in forward and reverse ballistic impact was established.Based on ?57mm and ?152mm gas gun and DIC technique,the forward and reverse Taylor experiments were performed.The equivalent conditions have been verified through comparisons between experimental and simulation results.Then forward and reverse ballistic experiments of hollow rod,oblique impact experiments of free-free beam and reverse ballistic non-normal penetration experiments were conducted,which proves that the equivalent condition is independent of specimen structure and impact angle,and justifies the universality of this theory.(2)Dimensional analysis was used to analyze the scale effects of structural deformation during the impact process.Similar rules between model and prototype of strain rate sensitive materials structural deformation were obtained,and the correction method was proposed.Non-geometric similar law was verified by "numerical experiments",and the influence of fillers on the deformation of hollow thick-wall rod was analyzed.Results show that the existence of the fillers affects the radial deformation of hollow rod,but the effect on the radial deformation of hollow rod between different fillers is not obvious.(3)Based on the ?152mm gas gun launching system,a new kind of reverse ballistic experimental technique was developed,the reverse ballistic experiments of projectile non-normal penetrating to the 2024-0 A1 target were carried out,and the DIC measuring technique was used in the experiment to measure the real-time response of projectile.The projectile responses at oblique angle,yaw angle and both oblique and yaw angle penetration conditions were compared.The axial force,shearing force and bending moment were analyzed by simulation.,and the response characteristics of projectile at different impact conditions were obtained.(4)The theory of free-free beam under axial and transverse load was improved,the yield function determination conditions of beam under axial and transverse load were introduced,and the structural dynamic response model of free-free beam was proposed.Based on the cavity expansion theory of metal material and the free surface effect of non-normal penetration,the resistance of projectile in penetration process was given.The projectile structural response models in different oblique angle,yaw angle and both oblique and yaw angle were established to analyze the dynamic response,the calculation results agree well with the experimental data.(5)To reduce the structural response of projectile and optimize the force environment,a double-ogive nose projectile was designed and the effects of different nose shapes on penetration performance were discussed.The mechanism analysis and experimental results show that,the double-ogive nose projectile has a smaller resistance and better structural stability.