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About this book

This short monograph presents an analysis and design methodology for shape memory alloy (SMA) components such as wires, beams, and springs for different applications. The solid-solid, diffusionless phase transformations in thermally responsive SMA allows them to demonstrate unique characteristics like superelasticity and shape memory effects. The combined sensing and actuating capabilities of such materials allows them to provide a system level response by combining multiple functions in a single material system. In SMA, the combined mechanical and thermal loading effects influence the functionality of such materials.

The aim of this book is to make the analysis of these materials accessible to designers by developing a "strength of materials" approach to the analysis and design of such SMA components inspired from their various applications with a review of various factors influencing the design process for such materials.

Table of Contents

Frontmatter

Chapter 1. Introduction to Shape Memory Alloys

Abstract
Classical materials like metals and alloys have played a significant role as structural materials for many centuries. Engineers have designed components and selected alloys by employing the classical engineering approach of understanding the macroscopic properties of the material and selecting the appropriate one to match the desired functionality based on the application. With advancements in material science and with increasing space and logistical limitations, scientists have been constantly developing high performing materials for various applications.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 2. Need and Functionality Analysis

Abstract
Generally the word “smart” is used synonymously with “intelligent,” but in reality the dictionary definition of “smartness” is “marked by often sharp forceful activity or vigorous strength,” that is, it is active. Thus, a “smartphone” can only wake you up with an alarm, but in reality it is smart only if it can “slap” you if you don’t wake up!
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 3. Manufacturing and Post Treatment of SMA Components

Abstract
We would like to briefly review the different manufacturing techniques and post-treatment techniques employed in the SMA community. This is by no means an exhaustive discussion but a broad overview of some important items. As designers, it is important to having an understanding of these details especially as many of these techniques/treatments discussed here influence the performance of the component immensely.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 4. Basic SMA Component Geometries and Responses

Abstract
SMA components must allow for a large surface area compared to their volume in order for them to be able to be cooled rapidly and repeated use at reasonable actuation frequencies. Thus SMAs are commonly used in the form of wires/rods, springs, tubes or beams under different loading conditions (tension, torsion or bending) for exploiting their unique characteristics in many practical applications. All these geometries are governed by their high surface to volume ratios.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 5. Factors Influencing Design of SMA Actuators

Abstract
Given the complex nonlinear nature of SMA responses, understanding their coupled thermomechanical responses of different components has been of significant interest for both researchers and application developers.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 6. Graphical Description of Temperature Controlled Actuation of SMA Wires

Abstract
In this chapter, we will demonstrate how the SMA wires and springs are actuated and the way a given stroke is achieved by means of temperature changes.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 7. Case Studies in the Preliminary Design of SMA Actuators

Abstract
In spite of the rather complex and hysteretic behavior of SMA components (wires and springs), and the complex changes that occur in their microstructures, the preliminary design of SMA wires and springs turns out to be reasonably simple provided we utilize their shape memory characteristics in specific ways. Designing SMA actuators requires defining actuation intervals (temperature profile), load levels and/or displacement outputs over its intended designed life. The alloy composition dictates the transformation temperatures and the component’s operating range. SMA components could be functional under load controlled or displacement controlled or simultaneous load and displacement controlled setups.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 8. Coupling SMA Actuators with Mechanisms: Principle of Virtual Work

Abstract
In Chap.7, we covered the basics of SMA wire and spring design for dead loading conditions. We noted that if the stroke required is very large, a simple SMA wire may be unfeasible.Thus, successful design of a shape memory wire actuator depends upon the ability to combine it with a mechanism to achieve the desired force and stroke when actuated.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy

Chapter 9. Fatigue of SMAs

Abstract
With growing applications of SMA components in different engineering applications, the issue of material performance over its designed life is of great concern to researchers lately. Fatigue studies in SMAs is still an unsolved puzzle and we wish to highlight some important items that affect the designers and some open questions in SMA fatigue areas.
Ashwin Rao, A. R. Srinivasa, J. N. Reddy
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