Theoretical And Numerical Study On Perforation Of Double-Layered Metal Targets Struck By Flat-ended Projectiles

The deformation of double-layered metal targets struck by flat-ended projectiles is numerically simulated in this dissertation.On the basis of relevant theories and numerical results obtained,a theoretical model for perforation of double-layered metal target without spacing is also proposed.The main results obtained are as follows:1.A quarter model is built and meshing using the meshing software True Grid.Numerical simulations have carried out for the perforation double-layered metal targets using ABAQUS/EXPLICIT with the modified Johnson-Cook constitutive relationship.The numerical results show that the first layer fails through shear with smaller global deformations;while the second layer is combined tensile and shear failure with larger global deformations.(1)For monolithic and double-layered targets without spacing,the ballistic limits of monolithic targets and double-layered targets with equivalent thickness are more or less the same when the total thickness is larger than the critical thickness at which adiabatic shear plugging occurs,when the thickness is greater than the critical value,the ballistic limits of monolithic targets and double-layered targets are obviously higher.(2)For double-layered target with spacing,the influence of spacing on the ballistic limits of double-layered targets is small when the total thickness is small;when the thickness is large,the ballistic limit firstly increases and then drops and finally reaches a fixed value with increase of space,which is bigger than the ballistic limit of the double-layered targets without spacing.(3)For double-layered targets without spacing,when the total thickness is small,the influence of the combination of different thickness as the two layers on the ballistic limit is small;when the total thickness is large,the ballistic limit will firstly increase,then fluctuate near the maximum,and then drop,finally fluctuate near the minimum,and the ballistic limit of a thinner plate in front of the thicker is higher than that of the reverse order.2.Anew theoretical model is proposed for the perforation of double-layered metal targets without spacing.This model is constituted based on Wen-Jones model and numerical results obtained,and strain failure criterion is employed to predict the ballistic limit of double-layered metal target struck normally by a flat-ended projectile.It's found that the present model predictions are in good agreement with available experimental data and numerical results.It is also found that when the total thickness is larger than the critical thickness at which adiabatic shear plugging occurs,the ballistic limits for double-layered metal targets are considerably higher than those for the corresponding monolithic metal plates;and that when the total thickness is less than the critical value,the ballistic limits are more or less the same for both targets.