Mechanical Engineering Department, Faculty of Engineering, Yasouj University, P.O. Box: 75914-353, Yasouj, Iran
In this article, some theoretical relations are derived to predict instantaneous axial load during the splitting process of square columns on rigid pyramidal dies. For this purpose, it is assumed that kinetic energy is dissipated by four different deformation mechanisms: bending, friction, crack propagation and expansion. These mechanisms are carefully assessed. Based on the principle of energy conservation, external work of axial force is equated with total dissipated energies during the plastic deformation; and final relations are obtained to predict load-displacement diagram. Also, curl radius of square columns during the splitting process is calculated theoretically. Then, some metal tubes are tested and compressed axially between a rigid platen and a pyramidal die. Cracks propagate along four corners of the column. Experiments show that all four free end sides roll up into curls with a constant radius and applied load becomes constant after the crack propagation. This mechanism results in a large stroke and a constant load. Therefore, splitting is introduces as an energy absorber mechanism with large stroke to length ratio and high specific absorbed energy. Comparison of the theoretical predictions by derived equations with the experimental results shows a good correlation.