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Split Hopkinson pressure bars (SHPB) technique has been widely used to characterize dynamic mechanical properties of various materials, and one of its basic assumptions is uniform deformation of specimen during the experiment. However, some studies in recent years have found the obvious deformation localization within metal foam specimens in SHPB tests, which may violate the basic assumption and lead to unreliable result. In this paper, we carried out numerical SHPB-test to study the problem based on the experimental verification. The specimens of metal foam are modeled to have 3D meso structures with given matrix mechanical properties. Numerical SHPB-tests of aluminum foam specimens with varying thickness at different strain rates were performed. Deformation non-uniformity in each local region of the specimen was examined, and the influences of specimen thickness and testing strain rate on the deformation non-uniformity were quantitatively analyzed as well as the size effect. Criteria to judge the reliability of characterizing dynamic mechanical properties of metal foam by SHPB test were proposed.

SHPB; metal foam; dynamic properties; deformation non-uniformity