Smart materials and structures

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SMART MATERIALS AND STRUCTURES_PPT

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SMART MATERIALS AND STRUCTURES

Lecture at Swiss Federal Institute of Technology Zurich (ETH) ¨

Zurich, 14 Sept.,2015 ¨

Bohua Sun

Member of Academy of Science of South Africa(ASSAf)

Professor in Engineering

Cape Peninsula University of Technology

Cape Town

South Africa

[email protected]

CAPE PENINSULA UNIVERSITY OF TECHNOLOGY (2015)

Copyright ⃝c 2015 by Bohua Sun. All rights reserved.

Published by Cape Peninsula Univerisity of Technology

Cape Town, South Afica.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form

or by any means, electronic, mechanical, photocopying, recording, scanning.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in

preparing this book, they make no representations or warranties with respect to the accuracy or

completeness of the contents of this book and specifically disclaim any implied warranties of

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but not limited to special, incidental, consequential, or other damages.

Smart Materials and Structures / Bohua Sun . . . [et al.].

Printed in South Africa.

To My Dear Father, Mother

and Family

[I hope that I may succeed in deserving and obtaining your confidence. But in the first place, I can

ask nothing of you but to bring with you, above all, a trust in science and a trust in yourselves.

The love of truth, faith in the power of mind, is the first condition in Philosophy. Man, because

he is Mind, should and must deem himself worthy of the highest; he cannot think too highly of the

greatness and the power of his mind, and, with this belief, nothing will be so difficult and hard

that it will not reveal itself to him. ]

—Georg Wilhelm Friedrich Hegel, Oct. 28, 1816 at Heidelberg University

PREFACE

Smart structures or smart materials systems are those which incorporate actuators and sen￾sors that highly integrate into the structures and have structural functionality, as well as

highly integrated control logic, signal conditioning, and signal power amplification elec￾tronics. Such actuating, sensing and controlling are incorporated into a structure for the

purpose of influencing its states or characteristics, be they mechanical, thermal, optical,

chemical, electrical, or magnetic. For example, a mechanically smart structure is capable

of altering both its mechanical states (its position or velocity) or its mechanical charac￾teristics (its stiffness or damping). Optically smart structures could, for example, change

color to match its background.

In the following decades, it is expected that there will be widespread application of

the technology under development, in its current and evolutionary forms. The breath of

application of this technology is expected not only towards high-tech but also towards

civilian fields.

This lecture notes is specially prepared for the Seminar at Institute of Structural Engi￾neering at ETH. I would like to take this opportunity to address important issues of smart

materials and structures and to introduce some work from my research group.

I would like to express my deep gratitude to Prof. Dr. Eleni Chatzi1

for his warm

hospitality and to the South African National Research Foundation for financial support.

BOHUA SUN

Cape Town, South Africa and Zu¨rich, Switzerland

1Prof. Dr. Eleni Chatzi is the Chair of Structural Mechanics at ETH

v

CONTENTS

Preface v

List of Figures xi

List of Tables xv

1 INTRODUCTION 1

1.1 The Needs 1

1.2 Smart Material Age 2

1.3 Smart Structures and Development Background 3

1.4 Smart Materials 4

1.5 Smart Structures 5

1.6 Critical Component Technologies of Smart Structures 6

1.7 Smart Materials and MEMS 7

2 SMART MATERIALS AND STRUCTURES 9

2.1 Piezoelectric Materials 9

2.1.1 General Concepts 9

2.1.2 Piezo Transducers 12

2.1.3 PZT Application 12

2.2 Shape Memory Materials 16

2.2.1 General Concepts 16

2.2.2 Ferromagnetic Shape Memory Alloys 18

vii

viii CONTENTS

2.2.3 SMA Application 19

2.3 Magnetostrictive Materials 20

2.3.1 General Concepts 20

2.3.2 Basics of Magnetostriction 22

2.3.3 MS Applications 23

2.4 Electrorheological Fluids 24

2.4.1 General Concepts 24

2.4.2 EF Applications 25

2.5 Magnetorheological fluids 25

2.5.1 Introduction to MR Fluids 25

2.5.2 MR Actuators 27

2.5.3 Design of MR Systems 29

2.6 Fibre Optic Sensors 30

2.6.1 The Structure of Optical Fibres 30

2.6.2 Characteristics, Advantages and Capabilities of Fibre Optic

Sensors 31

2.6.3 Capabilities and Significance 31

2.6.4 Intensiometric Fibre Optic Sensors 32

2.6.5 Interferometric fibre optic sensors 33

2.6.6 Bragg (Grating) Fibre Optic Sensor 33

2.6.7 Polarimetric Fibre Optic Sensors 34

2.6.8 Modalmetric Fibre Optic Sensors 34

3 DISTRIBUTED PIEZOELECTRIC ACTUATING SMART STRUCTURES 35

4 SOME GENERAL ASPECTS OF PIEZOELECTRIC SENSOR MECHANICS 41

4.1 Introduction 41

4.2 Smart structure and active control 41

4.3 Sensory Elements 42

4.4 Working Principle of Piezoelectric Smart Structures 43

4.5 Sensor Analysis 44

4.5.1 Piezo Composite Beam 45

4.5.2 Modal sensor 46

5 SMART PIEZO COMPOSITE MINDLIN BEAMS 47

5.1 Introduction 47

5.2 Formulations 48

5.3 Numerical Example 51

6 RECTANGULAR AND CIRCULAR SHAPE DISTRIBUTED PIEZOELECTRIC

ACTUATOR 55

6.1 Introduction 55