Experimental Study And Finite Element Simulation On Monotonic And Cyclic Deformation Behaviours Of Foam Aluminum Materials

Aluminum foam materials have been widely used in the areas of aerospace, automotive due to their good performances in lightweight, high specific rigidity, and high specific strength. Aluminum foam is mainly used as the filling in cushioning structures, and the mechanical researches are focused on the energy absorption of the foam under impact loading. With the extension of application, some aluminum foams are used in the structural components standing the applied loading. For the structural application, the quasi-static mechanical performances are very important, but there are quite few studies on the quasi-static mechanical of aluminum foam, especially on that presented under cyclic loading. In this paper, systematic experiments and finite element simulations have been carried out to study the monotonic and cyclic deformation behaviors of closed-cell and spherical open-cell aluminum foams.This paper mainly contains the following parts:Part1. The various experiments of closed-cell aluminum and spherical open-cell aluminum foam are performed, including the monotonic compression, monotonic tension and cyclic compression tests. The compression&tension characteristics and cyclic deformation behaviors are obtained for two kinds of aluminum foams with different cell shapes.Part2. The monotonic tension behaviors of aluminum foam are simulated by FEM method. The effects of structural parameters on the compression stress-strain responses are discussed. The discussed structural parameters include the porosity, pore diameter size and defects inside of cell. The simulated results show that, there are higher compressive strength and the plastic yield stress when aluminum foam has lower porosity or smaller pore diameter; the compression performance is influenced by the defects of cell also.Part3. The periodic boundary conditions are introduced into the simulation of aluminum foam subjected to monotonic compression. The simulated results are in agreement with the experimental results in tendency. For the cases with different porosities and pore diameters, the simulated results with periodic boundary conditions are compared with that with free boundary conditions. It is shown that the stresses with the periodic conditions is higher than that with the free boundary conditions under the same compression displacement, and the variation of compression stress-strain curves with periodic conditions is less than that with simplified boundary conditions.Part4. Based on the periodic conditions, the ratchetting behaviors of spherical open-cell aluminum foam under cyclic stressing are simulated by FEM method. The effects of meso-structure material parameters on the ratchetting behaviors are analyzed. The parameters include the porosity, pore diameter and the cell distribution and so on. The occurred places and the evolution of inelastic deformation inside of aluminum foam are observed and analyzed. The following conclusions are obtained. The porosity is the main factor influencing ratchetting deformation of aluminum foam. The uniform distribution or smaller pore diameter can increase the resistance of aluminum foam to ratchetting deformation, and smaller ratchetting occurs. The cyclic plastic deformations of aluminum foam are concentrated around the two sides of hole, and the angle between the deformation direction and load direction is45°.