A Concept of Shock Absorption Mechanisms Using Buckling Phenomena and Hysteretic Spring Elements

抄録

In this paper, a preliminary study on a shape-recoverable shock absorption structure consisting of hysteretic spring elements combined with a buckling mechanism which could achieve both high energy absorption efficiency and high energy dissipation efficiency is presented. In order to illustrate the basic idea, a conceptual model consisting of a two-link mechanism and a hysteretic spring is investigated. The two-link mechanism with axial and lateral springs is frequently used as an elementary model for the buckling behavior of thin-walled structures. Without the lateral spring, it has a pair of stable equilibriums and one unstable equilibrium between them, so that it shows a snap-through buckling instability when loaded in the lateral direction. The load-deformation curve changes depending on the quantity of the lateral spring constant undergoing saddle-node bifurcation. After the bifurcation, the stable and unstable equilibriums except for the origin vanish, and only one stable equilibrium remains at the origin. This implies that, when combined with a strong spring, the load-deformation curve of the two-link mechanism has only a stable equilibrium at the origin, whereas it has another stable equilibrium when combined with a weak spring. Therefore, if combined with an appropriate hysteretic spring, the mechanism subjected to an impact will yield positive resistive force in the loading path, followed by stopping at the stable equilibrium with residual deformation when unloaded. After the impact, the residual deformation will be eliminated by applying a small amount of energy to trigger the bifurcation again. A proof-of-concept experimental model consisting of a two-link mechanism and a superelastic shape memory alloy (SMA) spring is developed for the demonstrative purpose. A prototype of superelastic SMA-based “woven” shells is also developed to show a possible application of the proposed concept.