Two-dimensional analytical model and experimental validation of garter stitch knitted shape memory alloy actuator architecture

Julianna Abel, Jonathan Luntz, Diann Brei

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations

Abstract

Active knits are a unique architectural approach to meet the industrial need for high strain and simultaneous force generation. This paper presents an analytical state-based model to predict the actuation response of a Shape Memory Alloy (SMA) garter knit textile. Garter knits generate significant contraction against moderate to large loads when heated due to the continuous interlocked network of loops of SMA wire. For this knit architecture, the states of operation are defined based on the thermal and mechanical loading of the textile, the resulting phase change of the SMA, and the load path followed to that state. Transitions between these operational states induce either stick or slip frictional forces depending upon the state and path, which affect the actuation response. A load-extension model of the textile is derived for each operational state using Elastica Theory and Euler-Bernoulli beam bending for the large deformations within a loop of wire based on the stress strain behavior of the SMA material. This provides kinematic and kinetic relations which scale to form analytical transcendental expressions for the net actuation motion against an external load. The model was validated experimentally for an SMA garter knit textile over a range of applied forces with good correlation for both the load-extension behavior in each state as well as the net motion produced during the actuation cycle. Throughout the experiments, large strains (up to 250% recoverable, over 50% actuation strain) against moderate forces (order of tens of Newtons) were achieved which demonstrates promise for a wide range of applications.

Original languageEnglish (US)
Title of host publicationProceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems 2009, SMASIS2009
Pages353-368
Number of pages16
DOIs
StatePublished - 2009
Event2009 ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS2009 - Oxnard, CA, United States
Duration: Sep 21 2009Sep 23 2009

Publication series

NameProceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems 2009, SMASIS2009
Volume2

Conference

Conference2009 ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS2009
CountryUnited States
CityOxnard, CA
Period9/21/099/23/09

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