Theoretical investigation on the energy absorption of ellipse-shaped self-locked tubes

Self-locked energy-absorbing systems have been proposed in previous studies to overcome the limitations associated with the round-tube systems because they can prevent the lateral splash of tubes from impact loadings without any constraints. In case of self-locked systems, the ellipse-shaped self-locked tube is considered to be an optimal design when compared with the ordinary circle-shaped self-locked tubes and other shaped self-locked tubes. In this study, we aim to theoretically analyze the ellipse-shaped self-locked tubes. Further, a plastic hinge model is developed to predict the force-displacement relation of the tube, which is compared with the deformation process observed in the experiment and finite element method (FEM) simulation. Using this model, the effects of tuning the geometric parameters of the tube on the energy absorption performance, including the deformation efficiency, energy absorption capacity, and effective stroke ratio, are simulated and analyzed. Finally, a guideline is provided with respect to the design of the ellipse-shaped self-locked tube in engineering applications.