MECHANICS OF AIRCRAFT STRUCTURESPDF电子书下载

1 Characteristics of Aircraft Structures and Materials 1

1.1 Introduction 1

1.2 Basic Structural Elements in Aircraft Structure 2

1.2.1 Axial Member 2

1.2.2 Shear Panel 3

1.2.3 Bending Member (Beam) 4

1.2.4 Torsion Member 5

1.3 Wing and Fuselage 7

1.3.1 Load Transfer 7

1.3.2 Wing Structure 9

1.3.3 Fuselage 10

1.4 Aircraft Materials 11

Problems 15

2 Introduction to Elasticity 17

2.1 Concept of Displacement 17

2.2 Strain 19

2.3 Stress 24

2.4 Equations of Equilibrium in a Nonuniform Stress Field 26

2.5 Principal Stresses 27

2.5.1 Shear Stress 32

2.5.2 Revisit of Transformation of Stress 34

2.6 Linear Stress-Strain Relations 36

2.6.1 Strains Induced by Normal Stress 36

2.6.2 Strains Induced by Shear Stress 39

2.6.3 3-D Stress-Strain Relations 40

2.7 Elastic Strain Energy 44

2.8 Plane Elasticity 46

2.8.1 Stress-Strain Relations for Plane Isotropic Solids 47

2.8.2 Stress-Strain Relations for Orthotropic Solids in Plane Stress 50

2.8.3 Governing Equations 51

2.8.4 Solution by Airy Stress Function for Plane Isotropic Solids 52

Problems 53

3 Torsion 57

3.1 Torsion of Uniform Bars 57

3.2 Bars with Circular Cross-Sections 63

3.3 Bars with Narrow Rectangular Cross-Sections 65

3.4 Closed Single-Cell Thin-Walled Sections 69

3.5 Multicell Thin-Walled Sections 79

Problems 83

4 Bending and Flexural Shear 87

4.1 Derivation of the Simple (Bernoulli-Euler) Beam Equation 87

4.2 Bidirectional Bending 92

4.3 Transverse Shear Stress due to Transverse Force in Symmetric Sections 97

4.3.1 Narrow Rectangular Cross-Section 98

4.3.2 General Symmetric Sections 100

4.3.3 Wide-Flange Beam 102

4.3.4 Stiffener-Web Sections 103

Problems 104

5 Flexural Shear Flow in Thin-Walled Sections 107

5.1 Flexural Shear Flow in Open Thin-Walled Sections 107

5.1.1 Symmetric Thin-Walled Sections 108

5.1.2 Unsymmetric Thin-Walled Sections 113

5.1.3 Multiple Shear Flow Junctions 115

5.1.4 Selection of Shear Flow Contour 117

5.2 Shear Center in Open Sections 117

5.3 Closed Thin-Walled Sections and Combined Flexural and Torsional Shear Flow 124

5.3.1 Shear Center 125

5.3.2 Statically Determinate Shear Flow 129

5.4 Multicell Closed Sections 132

Problems 136

6 Failure Criteria for Isotropic Materials 141

6.1 Strength Criteria for Brittle Materials 141

6.1.1 Maximum Principal Stress Criterion 142

6.1.2 Coulomb-Mohr Criterion 142

6.2 Yield Criteria for Ductile Materials 145

6.2.1 Maximum Shear Stress Criterion (Tresca Yield Criterion) in Plane Stress 145

6.2.2 Maximum Distortion Energy Criterion (von Mises Yield Criterion) 147

6.3 Fracture Mechanics 151

6.3.1 Stress Concentration 151

6.3.2 Concept of Cracks and Strain Energy Release Rate 152

6.3.3 Fracture Criterion 154

6.4 Stress Intensity Factor 159

6.4.1 Symmetric Loading (Mode I Fracture) 159

6.4.2 Antisymmetric Loading (Mode II Fracture) 162

6.4.3 Relation between K and G 164

6.4.4 Mixed Mode Fracture 169

6.5 Fatigue Failure 169

6.5.1 Constant Stress Amplitude 170

6.5.2 S-N Curves 171

6.5.3 Variable Amplitude Loading 171

6.6 Fatigue Crack Growth 172

Problems 174

7 Elastic Buckling 179

7.1 Eccentrically Loaded Beam-Column 179

7.2 Elastic Buckling of Straight Bars 181

7.2.1 Pinned-Pinned Bar 183

7.2.2 Clamped-Free Bar 185

7.2.3 Clamped-Pinned Bar 187

7.2.4 Clamped-Clamped Bar 188

7.2.5 Effective Length of Buckling 190

7.3 Initial Imperfection 191

7.4 Postbuckling Behavior 193

7.5 Bar of Unsymmetric Section 199

7.6 Torsional-Flexural Buckling of Thin-Walled Bars 202

7.6.1 Nonuniform Torsion 202

7.6.2 Torsional Buckling--Doubly Symmetric Section 205

7.6.3 Torsional-Flexural Buckling 208

7.7 Elastic Buckling of Flat Plates 212

7.7.1 Governing Equation for Flat Plates 212

7.7.2 Cylindrical Bending 215

7.7.3 Buckling of Rectangular Plates 216

7.7.4 Buckling under Shearing Stresses 220

7.8 Local Buckling of Open Sections 220

Problems 223

8 Analysis of Composite Laminates 227

8.1 Plane Stress Equations for Composite Lamina 227

8.2 Off-Axis Loading 233

8.3 Notation for Stacking Sequence in Laminates 236

8.4 Symmetric Laminate under In-Plane Loading 238

8.5 Effective Moduli for Symmetric Laminates 241

8.6 Laminar Stresses 243

8.7 [±45??] Laminate 246

Problems 248

Index 251