Hydraulic shape memory alloy shock absorber: Design,analysis,and experiments

In this article, a new hydraulic shape memory alloy shock absorber is introduced. The shape memory alloy bars are used as the kernel components for energy dissipation and restoration in the stress mode of pure tension, and their initial deformation is enlarged by a hydraulic system with two pistons of different sizes. This particular arrangement yields high shape memory alloy material utilization and large displacement–length ratio simultaneously. A prototype device was fabricated and tested. The specific input energy (input energy/mass of shape memory alloy) and energy dissipation ratio (dissipated energy/input energy) in the experiments were about 2 J/g and 30%, respectively, at the full stroke. Based on this hydraulic shape memory alloy shock absorber, a combined device including viscous damping was theoretically investigated. According to the calculation results, the maximum specific input energy and energy dissipation ratio can increase by onefold from the initial model without viscous damping. Based on the works and results of this study, the three guidelines in the designing of shape memory alloy–based shock absorbers have been brought up: (1) keep the shape memory alloy parts in the pure tension state to increase the material utilization, (2) introduce deformation or displacement enlargement structures to amplify the work stroke, and (3) combine with other energy dissipation mechanisms.