Experimental Characterisation of the Deformation in Hollow Sphere Structures

摘要

Metallic hollow sphere structures (HSS) show structural parameters with less deviation in sphere diameter, cell wall thickness and architecture compared to other metallic foams. Therefore, it is possible to study the influence of these adjustable structural parameters on the mechanical properties. Tension and compression tests have been performed on HSS (hollomet~R). The spheres consist of stainless steel (316L) with a diameter of 4 mm. Two densities were used, 0.3 and 0.6 g/cm~3. HSS specimens with dense and porous sintered cell wall morphology were investigated. Furthermore, a 3D Honeycomb (3DHC) tike structure which was fabricated from HSS has been studied too. In compression the measured stress vs. strain curves exhibited a distinctive stress plateau, which is caused by the homogeneous cellular structure of the HSS. The doubling of the density resulted in 2.8 fold increase of the plateau stress, whereas the plateau strain remains almost constant. Tn-situ compression tests have been carried out in a scanning electron microscope (SEM) to investigate the local deformation mechanisms on the cell wall level, to compare these processes with other cell architectures (e. g. foams, 3DHC). In tension the doubling of the density caused a doubling of the ultimate tensile stress. The differences in the fracture processes and the effect of architectural parameters are discussed.