Papers by Author: Ling Ling Hu

Abstract: A numerical model of the aluminium foam with voronoi cells is built and uni-directionally crushed with various velocities from 1m/s to 110m/s. It is shown that the foam deforms homogeneously within the whole specimen and the stress in the foam increases gradually with the strain without an obvious plateau stage under the low-velocity compression, while the deformation is concentrated within a zone near the impact end and an obvious plateau stage can be found in the stress-strain curves of the foams under the high-velocity crushing. By analyzing the distribution of the density within the foams using the digital image processing technology, the densification strain of the foams under dynamic crushing can be determined. Then combining the foam’s stress-strain curve under the low-velocity compression, the dynamic plateau stress of the foams can be predicted. It is shown that both the densification strain and the plateau stress of the foams under the high-velocity crushing predicted by employing the digital image process technology are in good agreement with the numerical simulations. The results show that both the plateau stress and the densification strain of the foams increase with the impact velocity, which is essentially caused by the localization of the foam’s deformation under dynamic crushing.

Abstract: The constitutive relation for open-celled metal foams with random characteristics of cells was constructed based on the mechanical behavior and the distribution of the cells, which implied the effect of the mesoscopic characteristics of the cells on the macroscopic behavior of the foam. The constitutive relation was able to represent the whole three phases of the stress-strain curve of the open-celled metal foam with merely one expression. Besides, the explicit expressions for the foam’s yield strain and yield stress were supplied. Experimental data was employed to check the constitutive relation. It was found that the constitutive relation was able to represent accurately the whole compression process of the foams, and the calculated yield points had a good agreement with the experimental results.