材料力学PDF电子书下载

1 Introduction 2

1-1 Engineering and the Mechanics of Materials 4

1-2 Units and Numbers 5

International System of Units 5

U.S.Customary Units 5

Use of Numbers 6

1-3 Review of Statics 6

Free-Body Diagrams 6

Equilibrium 8

Structures 10

CONTENTS 11

About the Authors 11

Preface 13

Centroids 15

Distributcd Forces 17

Problems 21

2 Measures of Stress and Strain 28

2-1 Stresses 30

Traction,Normal Stress,and Shear Stress 30

Average Stresses 31

2-2 Strains 39

Extensional Strain 39

Shear Strain 41

Chapter Summary 45

Problems 46

3 Axially Loaded Bars 60

3-1 Stresses in Prismatic Bars 62

Stresses on Perpendicular Planes 62

Stresses on Oblique Planes 68

3-2 Strains in Prismatic Bars 72

Axial Strain andModulus ofElasticity 72

Lateral Strain and Poisson s Ratio 73

3-3 Statically Indeterminate Problems 81

Example 82

Flexibility and Stiffness Methods 83

3-4 Nonprismatic Bars and Distributed Loads 91

Bars with Gradually Varying Cross Sections 91

Distributed Axial Loads 93

3-5 Thermal Strains 100

3-6 Material Behavior 105

Axial Force Tests 105

Other Aspects of Material Behavior 110

3-7 Design Issues 112

Allowable Stress 113

Other Design Considerations 113

Chapter Summary 114

Problems 117

4 Torsion 136

4-1 Pure Shear Stress 138

State of Stress 138

Shear Modulus 138

Stresses on Oblique Planes 139

4-2 Torsion of Prismatic Circular Bars 141

Stresses and Strains 141

Polar Moment of Inertia 144

Positive Directions of the Torque and Angle of Twist 146

4-3 Statically Indeterminate Problems 149

4-4 Nonprismatic Bars and Distributed Loads 150

Bars with Gradually Varying Cross Sections 150

Distributed Torsional Loads 153

4-5 Torsiotn of an Elastic-Perfectly Plastic Circular Bar 156

4-6 Torsion of Thin-Walled Tubes 160

Stress 160

Angle of Twist 163

Cross Sections 167

4-7 Design Issues 167

Allowable Stress 168

Chapter Summary 171

Problems 174

5 States of Stress 186

5-1 Components of Stress 188

5-2 Transformations of Plane Stress 191

Coordinate Transformations 192

Maximum and Minimum Stresses 197

Constructing the Circle 206

5-3 Mohr s Circle for Plane Stress 206

Why Mohr s Circle Works 207

Determining Principal Stresses and the Maximum In-PlaneShear Stress 208

5-4 Principal Stresses in Three Dimensions 217

General State of Stress 218

Triaxial Stress 219

5-5 Design IssuesPressure Vessels 221

Spherical Vessels 221

Cylindrical Vessels 223

Allowable Stress 227

5-6 Tetrahedron Argument 228

Determining the Traction 228

Determining the Normal and Shear Stresses 230

Chapter Summary 233

Problems 236

6 States of Strain 248

6-1 Components of Strain 250

6-2 Transformations of Plane Strain 252

Strain Gauge Rosette 254

Maximum and Minimum Strains 257

6-3 Mohr s Circle for Plane Strain 264

Constructing the Circle 265

Determining Principal Strains and the Maximum In-Plane Shear Strain 266

6-4 Stress-Strain Relations 270

Linearly Elastic Materials 270

lsotropic Materials 271

Chapter Summary 279

Problems 284

7 Internal Forces and Moments in Beams 292

7-1 Axial Force,Shear Force,and Bending Moment 294

7-2 Shear Force and Bending Moment Diagrams 298

7-3 Equations Relating Distributed Load,Shear Force,and Bending Moment305 Chapter Summary 314

Problems 315

8 Stresses in Beams 322

8-1 Distribution of the Stress 324

Normal Stress 324

Geometry ofDeformation 325

Relation between Normal Stress and Bending Moment 328

Beams Subiected to ArbitraryLoads 330

8-2 Design Issues 338

Cross Sections 338

Allowable Stress 340

8-3 Composite Beams 343

8-4 Elastic-Perfectly Plastic Beams 347

8-5 Unsymmetric Cross Sections 355

Moment Exerted about a Principal Axis 355

Moment Exerted about an Arbitrary Axis 358

Shear Stress 362

8-6 Distribution of the Average Stress 363

Shear Formula 363

Rectangular Cross Section 366

8-7 Thin-Walled Cross Sections 371

8-8 Shear Center 377

Chapter Summary 385

Problems 390

9 Deflections of Beams 404

Differential Equation 406

9-1 Determination of the Deflection 406

Boundary Conditions 408

9-2 Statically Indeterminate Beams 414

Difierential Equation 419

9-3 Deflections Using the Fourth-Order Equation 419

Boundary Conditions 420

9-4 Method of Superposition 424

Chapter Summary 429

Problems 430

10 Buckling of Columns 438

10-1 Euler Buckling Load 440

10-2 Other End Conditions 447

Analysis of the Deflection 447

Effective Length 458

10-3 Eccentric Loads 461

Analysis of the Deflection 461

Secant Formula 464

Chapter Summary 467

Problems 469

11 Energy Methods 476

11-1 Work and Energy 478

Work 478

Strain Energy 480

Applications 482

11-2 Castigliano s Second Theorem 489

Derivation 489

Applications 491

Chapter Summary 496

Problems 498

12 Criteria for Failure and Fracture 502

12-1 Failure 504

Overloads 504

Repeated Loads 512

12-2 Stress Concentrations 520

Axially Loaded Bars 520

Torsion 521

Bending 524

12-3 Fracture 527

Overloads and Fast Crack Growth 528

Repeated Loads and Slow Crack Growth 535

Chapter Summary 539

Problems 542

Appendices 549

A Results from Mathematics 549

B Material Properties 555

C Centroids and Moments of Inertia 559

C-1 Centroids of Areas 559

C-2 Composite Areas 563

C-3 Moments of Inertia of Areas 566

C-4 Parallel Axis Theorems 570

C-5 Rotated and Principal Axes 577

Problems 583

D Properties of Areas 589

E Deflections and Slopes of Prismatic Beams 593

F Isotropic Stress-Strain Relations 599

G Answers to Even-Numbered Problems 605

Index 623