Title

Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

Authors

Authors

D. E. Nicholson; S. A. Padula; R. D. Noebe; O. Benafan;R. Vaidyanathan

Comments

Authors: contact us about adding a copy of your work at STARS@ucf.edu

Abbreviated Journal Title

Smart Mater. Struct.

Keywords

shape memory; thermomechanical behavior; springs; HELICAL SPRINGS; DEFORMATION; ACTUATORS; TRANSFORMATION; STABILITY; EVOLUTION; DESIGN; STRAIN; Instruments & Instrumentation; Materials Science, Multidisciplinary

Abstract

Transformation strains in high temperature shape memory alloys (HTSMAs) are generally smaller than for conventional NiTi alloys and can be purposefully limited in cases where stability and repeatability at elevated temperatures are desired. Yet such alloys can still be used in actuator applications that require large strokes when used in the form of springs. Thus there is a need to understand the thermomechanical behavior of shape memory alloy spring actuators, particularly those consisting of alternative alloys. In this work, a modular test setup was assembled with the objective of acquiring stroke, stress, temperature, and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were subjected to both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Finally, recognizing that evolution in the material microstructure can result in changes in HTSMA spring geometry, the effect of material microstructural evolution on spring performance was examined. This was done by taking into consideration the changes in geometry that occurred during thermomechanical cycling. This work thus provides insight into designing with HTSMA springs and predicting their thermomechanical performance.

Journal Title

Smart Materials and Structures

Volume

23

Issue/Number

12

Publication Date

1-1-2014

Document Type

Article

Language

English

First Page

13

WOS Identifier

WOS:000345275400010

ISSN

0964-1726

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