Abstract:

In order to improve the dynamic properties of uniform cellular materials, a 2D and a 3D density graded metal hollow sphere (MHS) arrays are investigated by explicit finite element method (FEM) simulation of in-plane crushing of sphere systems. The grading is established by changing sphere wall thickness. Pattern transformation from a square lattice to a hexagonal one, or SC lattice to BCC or FCC lattice is formed at a low impact velocity as observed in experiments. The emphasis is placed on the influence of gradient profile, as well as density gradient, on the energy absorption of materials under high impact velocities. The relation between material dynamic responses and gradients as well as impact velocities is established for design purpose. The results show that through the density gradient design of the MHS arrays, we could control the stress distribution and the energy absorption in the arrays, which provides a strategy in the dynamic morphology design of porous materials.