Numerical Study And Application Of Plastic Dynamic Response Of Metal Square Plates

There are important theoretical and actual values to study the plastic dynamic response of thin metal plates for the research of ribbon boating bridge and hull structures against blast and the mechanisms of protective structure against bullet. Based on experimental data, thorough analyse of plastic deformation and crack of thin metal square plates subjected to impulsive loads was carried out because of the insufficient published results and the need of the supervisor's research project. The results are applied to the study on the back-plate of ceramic/steel composite target against armor piercing projectile. The main contents and innovative work are as follows:(1) Based on published experimental data, plastic deformation and rupture of clamped, simply supported or unilateraly supported metal square plates subjected to uniform impulse were analyzed with numerical simulation. It shows that there is larger in-plane displacement at the boundaries of unilateraly supported square plates, which alters the distribution of stress and strain, prolongs the dynamic response time and increases the plastic deformation and the rupture impulse. The rupture impulse of unilateraly supported square plate is 1.524 times and 1.067 times larger compared with clamped and simply supported square plates, respectively.(2) Plastic deformation and rupture problem of metal square plates subjected to localized impulse loads were studied with numerical simulation. The results indicate that the deformation, the crack location and rupture impulse are all affected by the loading areas. Under the same impulse, the in-plane displacement and deformation increase with the increase of loading area, and the deformation energy reduces reversely. The rupture location changes when the loading area alters. The rupture impulse of unilaterally supported plate is higher than that of the clamped square plate, and the increase is more with larger loading area.(3) The tests of ceramic/mild steel composite target with clamped or semi-unilateraly supported back-plates against 7.62mm armor piercing projectile were performed. It is the first time that the impact effect of the bullet imposed on the back-plate through the ceramic is equaled to localized impulsive loads by numerical simulation. The loading space distribution and the loading time of rectangular impulse are established.(4) The buckling of the back-plate was investigated. The result indicates that there is plastic buckling at the boundary of semi-unilateraly supported back-plates. The buckling reduces center deflection and increases the deformation energy, and the ballistic limit velocity of the target increases accordingly. The effect of the back-plate thickness is also studied. The results show that there is no buckling at the boundary when the thickness h≥2.2mm.