Effects of Curvature of the Cross-section on the Buckling Characteristics and Buckling Shape of the Convex Tape-shaped Ti-Ni Shape Memory Alloy Element

Abstract

The negative stiffness exhibited by shape memory alloys (SMA) during buckling can be applied to passive vibration isolators and force-limiting mechanisms. However, to apply the negative stiffness of SMA, it is necessary to calculate the negative tangential stiffness value and buckling load of the shape memory alloy after buckling by design. In our previous study, we have shown that it is possible to increase the negative tangential stiffness and buckling load after buckling by increasing the curvature of a plate-like SMA material in the form of a convex tape with a given cross-sectional curvature. In this study, it is considered that the cause of the negative tangential stiffness after buckling is the change in martensitic phase transformation behavior during buckling deformation due to the addition of curvature to the cross-section. The results showed that the phase transformation behavior of a flat SMA element and a convex tape SMA element with curvature in its cross section changed. As a result, it was found that the flat SMA element does not exhibit negative stiffness immediately after buckling because martensitic phase transformation does not occur in the center of the specimen immediately after buckling, while the convex-tape SMA element tends to exhibit negative stiffness from immediately after buckling due to martensitic phase transformation in the center of the specimen.