Deformation and rotary driving characteristics of a shape-memory alloy thin strip element

Abstract

If a shape-memory alloy (SMA) thin strip is applied to elements subjected to torsion, a rotary driving element with a simple mechanism can be developed. With this purpose in view, torsion, recovery torque and torsion fatigue tests were carried out for a TiNi SMA thin strip, and the basic torsion characteristics of the strip were obtained. It was found that torque and recovery torque both increase in proportion to the angle of twist and temperature, and that the recoverable strain energy increases in proportion to temperature, while dissipated work decreases slightly with an increase in temperature. Fatigue life decreases in proportion to the angle of twist, and the fatigue life of a heat-treated material is longer than that of an as-received material. The angle of twist at the fatigue limit for the heat-treated material is almost the same as for the as-received material. As a practical application for a rotary driving element of this type, a means of opening and closing a door with an element driven by an SMA thin strip is demonstrated. © 2008 The Japan Institute of Metals.