Yield behavior of aluminum foam under multi-axial loading

In the current work, the initial yield behavior of closed-cell aluminum foams with three different relative densities under complex stress states have been investigated. A total of 16*3 (three different relative densities of closed-cell aluminum foam) experiments were conducted, which included uniaxial compression, uniaxial tension, combined tension-shear, and triaxial compression tests. Experimental results show that the initial yield behavior of closed-cell aluminum foam is isotropic and is associated with the first invariant of stress tensor, the second and third invariants of deviatoric stress tensor. A constitutive model to describe yield behavior of closed-cell aluminum foam was proposed and the relationship between the first invariant of stress tensor and the second invariant of deviatoric stress tensor was analyzed. Furthermore, tension-compression strength asymmetry of foams was introduced in the proposed model.