Effect of low density, low strength polyurethane foam on the energy absorption characteristics of circumferentially grooved thick-walled circular tubes

In this paper, analytical and experimental investigations are performed on the energy absorption characteristics of circumferentially grooved thick-walled circular tubes filled with low density and very low strength polyurethane foam typical of cushioning material. Thick-walled grooved tubes filled with low density foam are prepared for experiments. The results are also compared with the ones for the geometrically identical empty tubes. Employing the Taguchi method for designing the geometrical parameters of the specimens leads to a suitable range of groove length-to-wall thickness ratios to be covered. Based on the concept of energy dissipation through the circumferential plastic hinges during the successive folding of the specimens, an analytical approach is proposed. In addition, the amount of energy dissipated due to the interaction between tube metal and foam material is expressed by a conventional semi-empirical equation. A new constant, C-av, for low strength foam material is found by fitting the experimental data. The modified analytical model is in reasonable agreement with the experiments. This may indicate the validity of the proposed analytical model. The obtained results show that grooved thick-walled tubes filled with low strength foams can offer favorable energy absorption capacity and stability. Euler buckling is prevented due to the grooves and specific energy absorption is increased approximately twice that of the empty tubes. Structural effectiveness is increased nearly two times that of the empty tubes. (C) 2013 Elsevier Ltd. All rights reserved.