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.
Highlights
Shape memory alloy (SMA) is a metallic material that has the ability to recover its shape after deformation due to phase transformation [1,2]
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, and the application of the convex tape-shaped SMA elements to passive vibration isolator devices and force limit devices was investigated
When the buckling deformation is above 1 mm, the negative stiffness gradient tends to become almost constant regardless of the cross-sectional shape and buckling direction
Summary
Shape memory alloy (SMA) is a metallic material that has the ability to recover its shape after deformation due to phase transformation [1,2]. Shape memory alloys may recover their shape autonomously or by heating, depending on the temperature and stress environment. This autonomous shape recovery is called superelasticity, while shape recovery by heating is referred to as the material’s shape memory properties. Applications of the superelasticity of Ti-Ni SMA include medical products such as orthodontic wires and self-expanding stents [6,7], as well as consumer products such as eyeglass frames. Applications of the shape memory properties of Ti-Ni SMA include in medical devices such as the brain spatula (retractor) [8], and consumer devices such as temperature sensors [9] and haptic devices [10]
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