Study on Buckling Characteristics of a Convex Tape-Shaped Ti-Ni Shape Memory Alloy Element for Application to Passive Vibration Isolator Devices and Force Limit Devices

Abstract

The tape-shaped Ti-Ni shape memory alloy (SMA) shows negative or quasi-zero stiffness during post-buckling deformation, and this characteristic can be applied to passive vibration isolator devices and force limit devices. Design calculation of the buckling load and the negative stiffness gradient after buckling of tape-shaped SMA element are required to apply the SMA element to these devices. When the cross-section of the SMA element is convex tape shaped, an improvement in buckling properties is expected. In this study, the effects of the curvature of the cross-section on the buckling characteristics of convex tape-shaped SMA elements were investigated by the 3D finite element method (3D-FEM) and material testing. The results of the study indicate that the buckling load and negative stiffness gradient of convex tape-shaped SMA elements tend to increase with increasing curvature of the cross-section. Furthermore, when the convex tape-shaped SMA elements buckled in the convex direction of the cross-section, the loading stress was approximately equivalent to that of buckling a flat tape-shaped SMA elements. Therefore, the convex tape-shaped SMA element is considered to be more suitable for device application compared to the flat tape-shaped SMA element, because the buckling characteristics of convex tape-shaped SMA elements can be controlled by adjusting the curvature of the cross-section without changing the dimensions.