"A Numerical/Experimental Study of Nitinol Actuator Springs"

Wednesday, May 22, 2013: 11:45
Congress Hall 1 (OREA Pryamida Hotel)
Dr. Marco Urbano , SAES Getters S.p.A, Lainate, Italy
Prof. Ferdinando Auricchio , University of Pavia, Pavia, Italy
Dr. Giulia Scalet , UniversitÓ di Bologna, Bologna, Italy
Shape Memory Alloy (SMA) helicoidal springs can be seen as devices that combine an actuator, a
sensor (typically a temperature sensor), and a displacement amplifier. A single component
is indeed a system able to accomplish complex functions like reacting to a temperature
variation with an actuation.
Helicoidal springs are finding more and more applications, particularly in systems where
temperature is governed by a liquid medium, or where fast response is not required.
Despite the apparent simplicity, the behavior of SMA helicoidal springs is rather complex
and the design of such devices may possibly take advantage of numerical simulations.
In this work, we utilize three different constitutive models of Shape Memory Alloys, presented by Souza et al. (1998), Auricchio et al. (2011) and Auricchio and Bonetti (2012), in a finite element model to simulate the behavior
of helicoidal springs. The constitutive model parameters are calibrated by means of two
temperature loops carried out at different constant tensile loads on straight wires that
experienced identical annealing process.
Helicoidal springs are tested under temperature cycling at constant load and deformation
cycling at constant temperature. Through the comparison with experimental results,
different issues will be discussed, like the effect of large displacement and large
deformations, the effect of R-phase and functional fatigue.