In-situ strain measurement of shape memory alloy fiber during the austenitic and martensitic phase transformation
Journal
Smart Materials and Structures
Journal Volume
30
Journal Issue
9
Date Issued
2021
Author(s)
Abstract
Fibers made from shape memory alloys perform strain recovery during phase transformation of crystal structure. Controlled parameters such as heating time, holding temperature, and cooling time dominate the micro deformation of shape memory alloy fiber (SMAF). Mechanical contraction occurs at high temperature (austenitic phase), and strain-relief happens at low temperature (martensitic phase). But the rapid change of temperature causes unfinished or incomplete phase transformation, which induces residual strain within the SMAF. The accumulated defects shorten the specimen's life during cyclic loading and lower the limit of fatigue failure. This study uses digital image correlation to provide the in-situ response temperature-strain relations during the phase transformation and quantizes the residual strain within the SMAF. Experiments accurately control the holding temperature of SMAF in three conditions, which are (a) under, (b) around, and (c) beyond the phase transformation temperature of the specimen, and systematically analyzes the self-accommodation and strain-recovery of SMAF in the three experiments. The in-situ measurement of microscale deformation can help the end-user optimize the control parameters and increase the life and performance of SMAF. ? 2021 IOP Publishing Ltd.
Subjects
digital image correlation
multi-physics effects
phase transformation temperature
shape memory alloy
temperature-strain relation
thermal-mechanical reactions
Austenite
Austenitic transformations
Crystal structure
Deformation
Martensite
Martensitic transformations
Strain measurement
Temperature
Thermal fatigue
Change of temperatures
Digital image correlations
Martensitic phase transformations
Mechanical contraction
Microscale deformation
Phase transformation temperature
Response temperatures
Shape memory alloy fibers
Shape-memory alloy
Type
journal article