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The impact of a rigid body(protected structure) together with cushion material(cellular metal foam) on hard ground from a fixed height was investigated.An analytical one-degree-of-freedom colliding model(ODF-CM) was established to analyze the protection ability and energy absorption by the foam under low velocity impact conditions.For validation,drop hammer experiments were carried out for high porosity closed-cell aluminum foam specimens subjected to low velocity impact loading.The dynamic deformation behavior of the specimen was observed and the velocity attenuation of the drop hammer was measured.The results demonstrated that the aluminum foam had excellent energy absorption capabilities,with its dynamic compressive behavior similar to that obtained under quasi-static loading conditions.Finite element method(FEM) was subsequently employed to obtain stress distributions in the foam specimen.As the propagating period of stress in the specimen was far less than the duration of attenuation,the evolution of the stress was similar to that under quasi-static loading conditions and no obvious stress wave effect was observed,which agreed with the experimental observation.Finally,the predicted velocity attenuation by the ODF-CM was compared with both the experimental measurements and FEM simulation,and good agreements were achieved when the stress distribution was considered to be uniform and the “quasi-static” compressive properties are employed.
The impact of a rigid body (protected structure) together with cushion material (cellular metal foam) on hard ground from a fixed height was investigated. An analytical one-degree-of-freedom colliding model (ODF-CM) was established to analyze the protection ability and energy absorption by the foam under low velocity impact conditions. For validation, drop hammer experiments were carried out for high porosity closed-cell aluminum foam specimens subjected to low velocity impact loading. The dynamic deformation behavior of the specimen was observed and the velocity attenuation of the drop hammer was measured. The results demonstrated that the aluminum foam had excellent energy absorption capabilities, with its dynamic compressive behavior similar to that obtained under quasi-static loading conditions. Finite element method (FEM) was following employed to obtain stress distributions in the foam specimen. As the propagating period of stress in the specimen was far less than the duration of attenuat ion, the evolution of the stress was similar to that under quasi-static loading conditions and no obvious stress wave effect was observed, which agreed with the experimental observation. Finaally, the predicted velocity attenuation by the ODF-CM was compared with both the experimental measurements and FEM simulation, and good agreements were achieved when the stress distribution was considered to be uniform and the “quasi-static” compressive properties are employed.