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Experimental Mechanics of Solids and Structures

ISBN: 978-1-119-29232-6
176 pages
March 2016, Wiley-ISTE
Experimental Mechanics of Solids and Structures (1119292328) cover image

Description

From the characterization of materials to accelerated life testing, experimentation with solids and structures is present in all stages of the design of mechanical devices. Sometimes only an experimental model can bring the necessary elements for understanding, the physics under study just being too complex for an efficient numerical model. 

This book presents the classical tools in the experimental approach to mechanical engineering, as well as the methods that have revolutionized the field over the past 20 years: photomechanics, signal processing, statistical data analysis, design of experiments, uncertainty analysis, etc.

Experimental Mechanics of Solids and Structures also replaces mechanical testing in a larger context: firstly, that of the experimental model, with its own hypotheses; then that of the knowledge acquisition process, which is structured and robust; finally, that of a reliable analysis of the results obtained, in a context where uncertainty could be important. 

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Table of Contents

Foreword  ix

Introduction  xi

Chapter 1. Mechanical Tests  1

1.1. Introduction 1

1.2. Measurable quantities 2

1.3. Tensile test 3

1.3.1. Optimal testing conditions 5

1.3.2. Result of a standard tensile test 7

1.3.3. Stiffness of a tensile testing machine 9

1.4. Bending test  10

1.4.1. Test principle 10

1.4.2. Optimal realization conditions 10

1.4.3. Determination of flexural modulus  11

1.4.4. Damage to the structure 13

Chapter 2. A Few Sensors Used in Mechanics  15

2.1. Introduction 15

2.2. Strain measurement  15

2.2.1. Principle  15

2.2.2. Gauge factor  16

2.2.3. Description of a gauge  17

2.2.4. Conditioning  19

2.2.5. Multi-gauge assemblies 20

2.2.6. Compensation of bending effects 21

2.2.7. Effect of temperature 22

2.2.8. Measurement of a surface-strain tensor of an object  23

2.2.9. “Measurement” considerations 25

2.3. Displacement measurement 27

2.3.1. Principle  27

2.3.2. Key characteristics  27

2.4. Force measurement  28

2.4.1. Strain gauge load cell  28

2.4.2. Piezoelectric gauge load cell  29

2.5. Acceleration measurement  33

2.5.1. Principle  33

2.5.2. Selection criteria 37

Chapter 3. Optical Full-Field Methods  39

3.1. Overview  39

3.2. Selection of a field optical method 40

3.2.1. Factors governing selection 40

3.2.2. Fringe projection 41

3.2.3. Grid method  45

3.2.4. Digital image correlation  49

3.2.5. Speckle interferometry (ESPI)  53

3.3. Main processing methods of photomechanical results  60

3.3.1. Metrological aspects 60

3.3.2. Correction of target distorsions 62

3.3.3. Denoising in mapping  63

3.3.4. Phase unwrapping  65

3.3.5. Derivation of a displacement map 66

Chapter 4. Basic Tools for Measurement Methods 71

4.1. Introduction 71

4.2. Measurement and precision 72

4.2.1. Calibration 72

4.2.2. Tests  75

4.2.3. Evaluating uncertainties 78

4.3. Experimental test plans  88

4.3.1. Preparation 90

4.3.2. Approach  91

4.3.3. Adjusting polynomial models by least squares 92

4.3.4. Linear factorial design without interaction  94

4.3.5. Linear factorial design with interactions 100

4.3.6. Quadratic design with interactions 104

4.3.7. Variance analysis 107

4.4. Hypothesis tests  109

4.4.1. General principle 109

4.4.2. 1st and 2nd order error: a test’s power  110

4.4.3. Choosing a statistical law  112

4.4.4. Examples  113

4.4.5. Test for model adjustment: a return to ANOVA analysis 114

Chapter 5. Exercises  117

5.1. Multiple-choice questions  117

5.2. Problem: designing a torque meter 118

5.2.1. Mechanical analysis 118

5.2.2. Electrical installation 119

5.2.3. Analyzing uncertainty  120

5.3. Problem: traction test on a composite 121

5.3.1. Sizing a traction test 121

5.3.2. Measuring 121

5.3.3. Photomechanics  122

5.4. Problem: optic fiber Bragg gratings  122

5.4.1. What happens when there is traction on the fiber?  123

5.4.2. What will the effective index become depending on the temperature and strain parameters?  124

5.4.3. Separating temperature and mechanics  124

5.4.4. Analyzing uncertainty  124

5.5. Problem: bending a MEMS micro-sensor 124

5.5.1. Suggesting a mechanical model for this problem  125

5.6. Problem: studying a 4-point bending system 126

5.6.1. Analyzing the device 126

5.6.2. Mechanical analysis 127

5.6.3. Analyzing uncertainties 127

5.6.4. Optical full field methods  127

5.7. Digital pressure tester: statistical tests 128

5.7.1. Discovering the statistical functions library 128

5.7.2. Estimating a confidence interval  128

5.7.3. Calculating a test’s power  128

Conclusion 131

Bibliography  133

Index 141

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