Modeling the Shape Memory Effect in Modern Alloys

Dr. Chuck Collins

Department of Mathematics
University of Tennessee at Knoxville

December 6, 1996

Abstract

Over the past 20 years, material science has discovered a family of materials with interesting and useful properties: the smart materials. These materials can be used as sensors and/or an actuators in a system, where their intelligent responses can take the place of external control. One important class of smart materials is the shape memory alloys (SMAs). A sample of a SMA can be bent, stretched and otherwise abused, yet it will return to its original shape when heated. A defining feature of SMAs is their ability to form a microstructure called twinning as a response to external forces. Twinning consists of fine-scale bands, where in each band the material has a uniform orientation, but in adjacent bands it takes on different but symmetry-related orientations.

In this talk, I will first look at some examples of SMAs and their applications. Then I will discuss the details of the shape memory response and the development of mathematical models used to understand these materials, in particular the phenomena of twinning. Finally, I will look at some of the computationals results I have obtained which exhibit this microstructure.