The Finite Element Analysis Of Dynamic Mechanical Behavior Of Novel Metal Cellular Materials

Cellular materials are widely used in aerospace, automotive industries, construction industries, wrappers, warships and protection engineering because of their high specific stiffness, strength, well ability of absorbing energy, good permeability and heat conduction ability. Cellular materials have been studied long before, from natural porous materials to honeycombs and metallic foams, including static performance and dynamic behavior, especially the deformation mechanism, energy absorbing ability and strain rate effect. With the development of technology the design and study of the light weight and high strength cellular materials become much more critical.In the paper, the dynamic properties of chral honeycomb and metallic hollow sphere foams are simulated systematically. The chral honeycomb is composed of cylindrical cell walls and ribbed plates which are tangent to the cylindrical cell walls. Honeycomb of different topological structures can be obtained by changing the direction and the number of the ribbed plates. Metallic hollow sphere foams are composed of many metallic hollow spheres welded each other. There are inter-space between the spheres and in the hollow spheres, thus metallic hollow sphere foams enhance the open-cell and the closed-cell properties. The stability of traditional cellular materials, no matter the open-cell foam or the closed-cell foam, is not well. With the updating of process technologies, the outer radius and the thickness of hollow spheres can be in proper control, therefore, the properties of metallic hollow sphere foams are much more stable and reliable.Experimental studies on these two kinds of cellular materials are limited due to the restrictions of experimental conditions, and the studies are mainly confined to the static and qusi-static properties. Little studies are about high speed impact, grade function, imperfection and stress enhancement. In the paper, following aspects are investigated in details:(1) the energy absorbing property of the chral honeycomb under outer plane dynamic compression is studied. The influence of some parameters on the mechanical property is discussed, and effects of through-holes on the cell walls are considered.(2) in order to research the effect of the relative density, impact velocity, base material and imperfection, three kinds of hollow sphere foams are constructed, which are uniform hollow sphere foam, density gradient hollow sphere foam and random hollow sphere foam. From the results, the chral honeycomb with the structure of one cylindrical cell wall and three ribbed plates performed best in energy absorbing, the structure of through-holes on the cell walls can absorb more energy per unit mass. The strength of the hollow sphere foam increases with the relative density and the impact velocity increasing. Density gradient hollow sphere foam performs better energy absorbing ability. Under the same overall relative density, the energy absorbed is maximum when the layer of highest relative density is placed at the impact side, on the contrary, the energy absorbed is minimum. Stress enhancement occurs when the cellular material is close to densification which is critical in engineering.