Mohammad Mahdi Abedi;Abbas Niknejad;Gholam Hossein Liaghat;Mohammad Zamani Nejad;
In this article, absorbed energy per unit of initial tube length, initial peak force and mean folding force in empty and polyurethane foam-filled simple and grooved specimens with circular cross section are investigated, experimentally. Results demonstrate that in the empty and foam-filled simple specimens, absorbed energy per unit of initial tube length, initial peak force and mean folding force are larger than the corresponding values of the empty and foam-filled grooved specimens, respectively. But, increment of absorbed energy due to the foam-filler in the grooved tubes is more than the corresponding value in the simple specimens. Also, diagrams of absorbed energy and folding force versus the grooves distance have the minimum value. Therefore, there is a critical value for the grooves distance and according to the application viewpoint, to produce a good energy absorber, the grooves distance is selected far from the critical grooves distance. The experimental results show that when the grooves distance (λ) decreases, deformation mode inclines to the concertina (regular) mode and when λ increases, the deformation mode inclines to the diamond mode. Finally, a semiempirical relation is derived to predict the initial peak force of empty and foam-filled grooved tubes.