The Experimental Validation of Pseudoelastic Shape Memory Sheet Elements in Tooling Applications

Abstract

Shape memory alloys (SMA) are capable to remember a previously programmed form even after strong deformation. The reversible deformation of pseudoelastic SMA takes place on the basis of stress-induced martensitic phase transformation. These alloys are also interesting for elastic spring and damping elements, making their use in a variety of different machining and tool applications conceivable. Examples are elastic spring elements in forceps or damping elements in the field of sawing applications. The use of sheet like pseudoelsatic elements is of particular relevance for applications in handheld- and machining-tools. High elastic deformability, the damping properties and the potential of setting a horizontal spring characteristic curve in SMA elements come with problems such as strong temperature dependence of the spring and damping characteristics, possible limitations on the durability due to aging effects in cyclically occurring loads. Therefore, it requires a more extensive characterization and validation of sheet-shaped NiTi spring and damping elements. Hence different sheet-shaped SMA elements are analyzed in this publication due to different bends and thicknesses as well as different heat treatments for programming shapes into the sheets. Prepared sheets are characterized, especially cycle dependent force to displacement and damping properties. The publication shows experimental results of this analysis for various SMA sheets and potential industrial applications in the field of machine tools.