A two species thermodynamic Preisach model for the torsional response of shape memory alloy wires and springs under superelastic conditions

A three-species model for simulating torsional response of shape memory alloy components using thermodynamic principles and discrete Preisach models

“…SMA springs and wires under torsional loading are preferred over conventional materials due to their ability to deliver large working strokes (i.e. using SME) and thus making them suitable contenders as thermal actuators [11–13]. Many pre-industrialized concepts of using SMAs as thermal actuators in the automotive industry for mirror adjustments, suspension adjustments for improved ride comfort, climate control, fuel management, etc., have been proposed (see figure 2 from [8]) [14].…”

“…SMA cables, rods, torque tubes as thermal actuators are also being used in tailoring inlet geometry and orientation, increase/decrease fan nozzle in various aerospace applications [9, 15–17]. The ability of superelastic SMA springs and wires to deliver near-constant forces over large strokes have made them better alternatives for space closure and tooth movement in orthodontic applications when compared against its counterparts like stainless steel, β -Ti or Co–Cr material systems [13, 18–24]. The associated hysteresis with SE responses have enabled large SMA beams and springs to find applications as damping elements in bridges, buildings and also in seismic resisting systems due to their excellent energy dissipation and re-centering capabilities [13, 25–30].…”

“…Mirzaeifar et al [44, 45] and Chapman et al [46] reduced the three-dimensional (3D) model developed by Boyd et al [47] and Qidwai et al [48] to predict the torsional response of SMA. Due to the lack of full 3D experimental data, the models are forcefully reduced to a special 1D pure shear case with the use of a von-Mises equivalent stress approach for a finite-element method (FEM) implementation [13]. Mirzaeifar et al [49] in their sequel work extended this idea to capture the superelastic response of large axially loaded SMA helical springs with and without accounting for curvature effects (i.e.…”

Introduction to Shape Memory Alloys

“…The ability of SMA to deliver large plateau strains over relatively constant forces/stresses makes them good candidates as actuators [28]. Due to different crystal structures of austenite and martensite, SMA's have different moduli over various parts of the superelastic response [see Fig.…”

Basic SMA Component Geometries and Responses

“…4.1. In applications, understanding SMA component responses under partial or fully transformed cases with internal loops is of particular importance as the entire response might not be utilized always and only a portion of the entire response (internal loop) might be of significance to designers [3,4]. The area of these smaller hysteretic internal loops depends on the extent of the loading and unloading levels that the component is subjected to during service within the transformation region (plateau region) [4].…”