| Recently, attention has been paid to porous shape memory alloys. This is because the alloys show large and recoverable deformation, i.e. superelasticity and shape memory effect. Due to their light weight and potential large deformations, porous shape memory alloys have been considered as excellent candidates for energy absorption materials.; In the present study, porous NiTi alloy with several different porosities are processed by spark plasma sintering (SPS). The compression behavior of the porous NiTi is examined with an aim of using it for a possible high energy absorbing material. Two models for the macroscopic compression behavior of porous shape memory alloy (SMA) are presented in this work, where Eshelby's inhomogeneous inclusion method is used to predict the effective elastic and superelastic behavior of a porous SMA based on the assumption of stress-strain curve. The analytical results are compared with experimental data for porous NiTi with 13% porosity, resulting in a reasonably good agreement.; Based on the study upon porous NiTi, an energy absorbing composite structure made of a concentric NiTi spring and a porous NiTi rod is presented in this PhD dissertation. Both NiTi spring and porous NiTi rod are of superelastic grade. Ductile porous NiTi cylindrical specimens are fabricated by spark plasma sintering. The composite structure exhibits not only high reversible force-displacement behavior for small to intermediate loading but also high energy absorbing property when subjected to large compressive loads. A model for the compressive force-displacement curve of the composite structure is presented. The predicted curve is compared to the experimental data, resulting in a reasonably good agreement. |
