Influence of the embedded structure on the EFP formation of compact terminal sensitive projectile

To improve the damage efficiency of compact terminal sensitive projectile with EFP warhead,it is vital to understand how the embedded structure(ES)affects the EFP forming performance.In this paper,the corresponding numerical investigation is focused on,in which the fluid-structure interaction(FSI)method and the experimental verification are used.Based on the obtained quantitative relations between the forming performance and a(the ratio of height to maximum radius of ES),an optimal design is further provided.The results indicate that:when the embedded structural length and width range 0.1e0.3D and 0.1e0.2D(D:diameter of EFP warhead)at a fixed volume,respectively,EFP forming velocity nearly keeps as a constant,1760 m/s;the height of ES has a dramatical effect on the propagating range of detonation wave,resulting in significant influence on the aerodynamic shape and length-to-diameter ratio of EFP;under the given constraints,the EFP length-diameter ratio can reach the optimal value2.76,when the height of ES is 0.22D.

Quasi-steady aerodynamic characteristics of Terminal Sensitive Bullets with short cylindrical portion

The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets(TSB)with lowaspect ratio,especially in terminal trajectory.Currently,there is little research in terms of the TSB andshort cylinder with two free ends,and particularly in this trajectory,where the scanning angleβand rollangle a vary over a broad range between 0°and 180.In this work wind tunnel experiments are firstconducted to learn the effects of Reynolds number and scanning angle on aerodynamic parameters forshort cylinder with aspect ratio L/D=1.Similar to infinite cylinder,for the short cylinder with two freeends,the drag crisis phenomenon still exists in the critical regime 1.7×10^(5)≤Re≤6.8×10^(5).Then 3Dsimulations are performed to demonstrate the aerodynamic characteristics of short cylinder and TSBover a broad range of Re,L/D,a and 6.The sensitivity analysis of time step and grid are presented as well.whenβ3=0,for short cylinder,the drag crisis phenomenon was also observed in the simulation,but notas obvious as in the wind tunnel test.In some attitudes,there is an obvious Karman vortexin the wake ofshort cylinder and TSB.The correlation between time-averaged aerodynamic coefficients and L/D,Re,a&l is discussed.The vortex shedding frequency and shear layer behavior are obtained for quasi-steadyand unsteady flow.Finally,the effect of end's shape on drag reduction and vortex shedding frequency isanalyzed.

Numerical Analysis on Static Mechanical Properties of the Periodic Multilayer Lattice Material

Lattice material is a typical periodic structural material, and the gaps of the lattice material are often used to carry filling materials. In order to satisfy the load-carrying requirements of a certain multifunction/structure integrated composite material, four different 3D periodic multilayer lattice materials were proposed in this paper, such as the square, the quadrate, the tetrahedron and the hexagon. The BEAM189 element in ANSYS was adopted to predict their static mechanical properties, and the Mises strength criterion was taken as the failure criterion. Based on the solution of FEM, the axial stress and displacement of the top surface were obtained. The results indicated that adopting the relative stiffness and the load-mass ratio as the overall assessment is effective to evaluate the overall bearing capacity of the multilayer lattice materials. Given the same cross-section size of the cellular configuration, the hexagon multilayer lattice material shows the relatively optimal overall bearing capacity in the four configurations, while the tetrahedron configuration performs the worst.