Fracture Mechanics

von: Alan T. Zehnder

Springer-Verlag, 2012

ISBN: 9789400725959 , 235 Seiten

Format: PDF, OL

Kopierschutz: Wasserzeichen

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Fracture Mechanics


 

Fracture Mechanics

4

Preface

6

References

6

Contents

8

Acronyms

12

Chapter 1: Introduction

16

1.1 Notable Fractures

16

1.2 Basic Fracture Mechanics Concepts

18

1.2.1 Small Scale Yielding Model

19

1.2.2 Fracture Criteria

19

1.3 Fracture Unit Conversions

20

1.4 Exercises

20

References

21

Chapter 2: Linear Elastic Stress Analysis of 2D Cracks

22

2.1 Notation

22

2.2 Introduction

22

2.3 Modes of Fracture

23

2.4 Mode III Field

23

2.4.1 Asymptotic Mode III Field

24

2.4.2 Full Field for Finite Crack in an In?nite Body

28

2.4.2.1 Complex Variables Formulation of Anti-Plane Shear

28

2.4.2.2 Solution to the Problem

29

2.5 Mode I and Mode II Fields

31

2.5.1 Review of Plane Stress and Plane Strain Field Equations

31

2.5.1.1 Plane Strain

31

2.5.1.2 Plane Stress

32

2.5.1.3 Stress Function

32

2.5.2 Asymptotic Mode I Field

32

2.5.2.1 Stress Field

32

2.5.2.2 Displacement Field

34

2.5.3 Asymptotic Mode II Field

36

2.6 Complex Variables Method for Mode I and Mode II Cracks

36

2.6.1 Westergaard Approach for Mode-I

37

2.6.2 Westergaard Approach for Mode-II

37

2.6.3 General Solution for Internal Crack with Applied Tractions

37

2.6.4 Full Stress Field for Mode-I Crack in an In?nite Plate

38

2.6.5 Stress Intensity Factor Under Remote Shear Loading

40

2.6.6 Stress Intensity Factors for Cracks Loaded with Tractions

41

2.6.7 Asymptotic Mode I Field Derived from Full Field Solution

41

2.6.8 Asymptotic Mode II Field Derived from Full Field Solution

43

2.6.9 Stress Intensity Factors for Semi-in?nite Crack

43

2.7 Some Comments

43

2.7.1 Three-Dimensional Cracks

44

2.8 Exercises

46

References

47

Chapter 3: Energy Flows in Elastic Fracture

48

3.1 Generalized Force and Displacement

48

3.1.1 Prescribed Loads

48

3.1.2 Prescribed Displacements

49

3.2 Elastic Strain Energy

50

3.3 Energy Release Rate, G

51

3.3.1 Prescribed Displacement

51

3.3.2 Prescribed Loads

52

3.3.3 General Loading

53

3.4 Interpretation of G from Load-Displacement Records

53

3.4.1 Multiple Specimen Method for Nonlinear Materials

53

3.4.2 Compliance Method for Linearly Elastic Materials

56

3.4.3 Applications of the Compliance Method

57

3.4.3.1 Determination of G in DCB Sample

57

3.4.3.2 Use of Compliance to Determine Crack Length

58

3.5 Crack Closure Integral for G

58

3.6 G in Terms of KI, KII, KIII for 2D Cracks That Grow Straight Ahead

62

3.6.1 Mode-III Loading

62

3.6.2 Mode I Loading

63

3.6.3 Mode II Loading

63

3.6.4 General Loading (2D Crack)

63

3.7 Contour Integral for G (J-Integral)

64

3.7.1 Two Dimensional Problems

64

3.7.2 Three-Dimensional Problems

66

3.7.3 Example Application of J-Integral

66

3.8 Exercises

67

References

69

Chapter 4: Criteria for Elastic Fracture

70

4.1 Introduction

70

4.2 Initiation Under Mode-I Loading

70

4.3 Crack Growth Stability and Resistance Curve

73

4.3.1 Loading by Compliant System

75

4.3.2 Resistance Curve

76

4.4 Mixed-Mode Fracture Initiation and Growth

78

4.4.1 Maximum Hoop Stress Theory

78

4.4.2 Maximum Energy Release Rate Criterion

80

4.4.3 Crack Path Stability Under Pure Mode-I Loading

81

4.4.4 Second Order Theory for Crack Kinking and Turning

84

4.5 Criteria for Fracture in Anisotropic Materials

85

4.6 Crack Growth Under Fatigue Loading

86

4.7 Stress Corrosion Cracking

89

4.8 Exercises

89

References

91

Chapter 5: Determining K and G

92

5.1 Analytical Methods

92

5.1.1 Elasticity Theory

92

5.1.1.1 Finite Crack in an In?nite Body

92

5.1.1.2 Semi-in?nite Crack in an In?nite Body

93

5.1.1.3 Array of Cracks Under Remote Loading

93

5.1.2 Energy and Compliance Methods

94

5.1.2.1 4-Point Bending Debond Specimen: Energy Method

94

5.2 Stress Intensity Handbooks and Software

95

5.3 Boundary Collocation

95

5.4 Computational Methods: A Primer

99

5.4.1 Stress and Displacement Correlation

99

5.4.1.1 Stress Correlation

99

5.4.1.2 Displacement Correlation

100

5.4.2 Global Energy and Compliance

100

5.4.3 Crack Closure Integrals

101

5.4.3.1 Nodal Release

101

5.4.3.2 Modi?ed Crack Closure Integral

102

5.4.4 Domain Integral

104

5.4.5 Crack Tip Singular Elements

105

5.4.6 Example Calculations

109

5.4.6.1 Displacement Correlation and Domain Integral with 1/4 Point Elements

110

5.4.6.2 Global Energy

110

5.4.6.3 Modi?ed Crack Closure Integral

111

5.5 Experimental Methods

112

5.5.1 Strain Gauge Method

113

5.5.2 Photoelasticity

115

5.5.3 Digital Image Correlation

116

5.5.4 Thermoelastic Method

118

5.6 Exercises

120

References

121

Chapter 6: Fracture Toughness Tests

123

6.1 Introduction

123

6.2 ASTM Standard Fracture Test

124

6.2.1 Test Samples

124

6.2.2 Equipment

126

6.2.3 Test Procedure and Data Reduction

126

6.3 Interlaminar Fracture Toughness Tests

127

6.3.1 The Double Cantilever Beam Test

127

6.3.1.1 Geometry and Test Procedure

127

6.3.1.2 Data Reduction Methods

128

6.3.1.3 Example Results

130

6.3.2 The End Notch Flexure Test

131

6.3.3 Single Leg Bending Test

132

6.4 Indentation Method

134

6.5 Chevron-Notch Method

136

6.5.1 KIVM Measurement

137

6.5.2 KIV Measurement

138

6.5.3 Work of Fracture Approach

139

6.6 Wedge Splitting Method

141

6.7 K-R Curve Determination

144

6.7.1 Specimens

144

6.7.2 Equipment

145

6.7.2.1 Optical Measurement of Crack Length

145

6.7.2.2 Compliance Method for Crack Length

145

6.7.2.3 Other Methods for Crack Length

145

6.7.3 Test Procedure and Data Reduction

147

6.7.3.1 By Measurement of Load and Crack Length

147

6.7.3.2 By Measurement of Load and Compliance

147

6.7.3.3 Indirect Approach Using Monotonic Load-Displacement Data

148

6.7.4 Sample K-R curve

148

6.8 Exercises

148

References

149

Chapter 7: Elastic Plastic Fracture: Crack Tip Fields

151

7.1 Introduction

151

7.2 Strip Yield (Dugdale) Model

151

7.2.1 Effective Crack Length Model

157

7.3 A Model for Small Scale Yielding

158

7.4 Introduction to Plasticity Theory

160

7.5 Anti-plane Shear Cracks in Elastic-Plastic Materials in SSY

164

7.5.1 Stationary Crack in Elastic-Perfectly Plastic Material

164

7.5.2 Stationary Crack in Power-Law Hardening Material

168

7.5.3 Steady State Growth in Elastic-Perfectly Plastic Material

170

7.5.4 Transient Crack Growth in Elastic-Perfectly Plastic Material

174

7.6 Mode-I Crack in Elastic-Plastic Materials

176

7.6.1 Stationary Crack in a Power Law Hardening Material

176

7.6.1.1 Deformation Theory (HRR Field)

176

7.6.1.2 Incremental Theory

179

7.6.2 Slip Line Solutions for Rigid Plastic Material

179

7.6.2.1 Introduction to Plane Strain Slip Line Theory

179

7.6.2.2 Plane-Strain, Semi-in?nite Crack

181

7.6.2.3 Plane-Stress, Semi-in?nite Crack

183

7.6.3 Large Scale Yielding (LSY) Example

183

7.6.4 SSY Plastic Zone Size and Shape

184

7.6.5 CTOD-J Relationship

186

7.6.6 Growing Mode-I Crack

187

7.6.7 Three Dimensional Aspects

191

7.6.8 Effect of Finite Crack Tip Deformation on Stress Field

193

7.7 Exercises

195

References

196

Chapter 8: Elastic Plastic Fracture: Energy and Applications

198

8.1 Energy Flows

198

8.1.1 When Does G=J?

198

8.1.2 General Treatment of Crack Tip Contour Integrals

199

8.1.3 Crack Tip Energy Flux Integral

201

8.1.3.1 Global Path Independence for Steady State Crack Growth

201

8.1.3.2 Energy Flux as Gamma->0

202

8.1.3.3 Energy Flux for Gamma Outside Plastic Zone

202

8.1.3.4 Thermal Field Visualization of Energy Flow

204

8.2 Fracture Toughness Testing for Elastic-Plastic Materials

206

8.2.1 Samples and Equipment

206

8.2.2 Procedure and Data Reduction

207

8.2.2.1 Test Procedure

207

8.2.2.2 Data Reduction

208

8.2.2.3 Validation of Results

209

8.2.3 Examples of J-R Data

210

8.3 Calculating J and Other Ductile Fracture Parameters

210

8.3.1 Computational Methods

211

8.3.2 J Result Used in ASTM Standard JIC Test

213

8.3.2.1 Rigid Plastic Material

215

8.3.2.2 Elastic Material

215

8.3.2.3 Elastic-Plastic Material

215

8.3.3 Engineering Approach to Elastic-Plastic Fracture Analysis

215

8.3.3.1 Sample Calculation

217

8.4 Fracture Criteria and Prediction

218

8.4.1 J Controlled Crack Growth and Stability

218

8.4.2 J-Q Theory

220

8.4.3 Crack Tip Opening Displacement, Crack Tip Opening Angle

223

8.4.4 Cohesive Zone Model

226

8.4.4.1 Cohesive Zone Embedded in Elastic Material

228

8.4.4.2 Cohesive Zone Embedded in Elastic-Plastic Material

229

References

231

Index

233