Fatigue and Fracture: Understanding the Basics

699 Pages·2012·9.16 MB·English

by  F. C. Campbell

FATIGUE
AND
FRACTURE
Understanding
the
Basics
edited
by
F.c. campbell
asM international®
Materials Park, Ohio 44073-0002
www.asminternational.org
Copyright © 2012
by
ASM International®
All rights reserved
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ASM International®
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Printed in the United States of America
Fatigue and Fracture—Understanding the Basics Copyright © 2012 ASM International®
F.C. Campbell, editor All rights reserved
www.asminternational.org
contents
Preface � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ix
ChaPter 1
Introduction to Fatigue and Fracture� � � � � � � � � � � � � � � � � � � � � � � 1
Industrial Significance of Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The Brittle Fracture Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Changes in Design Philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Life-Limiting Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
ChaPter 2
Mechanical Behavior � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 25
Tensile Properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Resilience and Toughness ................................. 33
True Stress-Strain Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Stress Concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Notched Tensile Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Shear and Torsion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Stress-Strain Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Combined Stresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Yield Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Residual Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Hardness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
ChaPter 3
Ductile and Brittle Fracture � � � � � � � � � � � � � � � � � � � � � � � � � � � � 55
Ductile Fracture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Brittle Fracture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Macroscopic Ductile and Brittle Fracture Surfaces. . . . . . . . . . . . . . 86
iv / Contents
Ductile-to-Brittle Transition in Steels . . . . . . . . . . . . . . . . . . . . . . . . 90
Intergranular Failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Causes of Steel Embrittlement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Combined Fracture Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
ChaPter 4
Fracture Mechanics� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 101
Griffith’s Theory of Brittle Fracture. . . . . . . . . . . . . . . . . . . . . . . . . 101
Linear Elastic Fracture Mechanics. . . . . . . . . . . . . . . . . . . . . . . . . . 104
Elastic-Plastic Fracture Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . .113
Charpy and Izod Impact Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
Drop-Weight Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Fracture Toughness Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Variables Affecting Fracture Toughness . . . . . . . . . . . . . . . . . . . . . 140
ChaPter 5
Fatigue of Metals� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 147
Stress Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
High-Cycle Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Low-Cycle Fatigue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Fatigue-Life Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Cumulative Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
Fatigue Crack Nucleation and Growth . . . . . . . . . . . . . . . . . . . . . . 170
Fracture Mechanics Approach to Fatigue Crack Propagation. . . . . 181
Crack Closure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
The Short Crack Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Geometrical Stress Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . 192
Manufacturing Stress Concentrations . . . . . . . . . . . . . . . . . . . . . . . 194
Fatigue-Life Improvement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Fatigue Design Methodologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
ChaPter 6
Fatigue and Fracture of engineering alloys � � � � � � � � � � � � � � � � 209
Fracture Toughness of Steels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Fatigue of Steels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
Fracture Toughness of Aluminum Alloys . . . . . . . . . . . . . . . . . . . . 228
Fatigue of Aluminum Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
Fracture Toughness of Titanium Alloys. . . . . . . . . . . . . . . . . . . . . . 240
Fatigue of Titanium Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
ChaPter 7
Metallic Joints—Mechanically Fastened and Welded � � � � � � � � 263
Mechanically Fastened Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
Threaded Fasteners in Tension. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
Contents / v
Bolts and Rivets in Bearing and Shear . . . . . . . . . . . . . . . . . . . . . . 275
Fatigue in Welded Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282
Methods for Improving the Fatigue Life of Welded Joints . . . . . . . 291
Fracture Control in Welded Structures. . . . . . . . . . . . . . . . . . . . . . . 293
Factors Affecting Fracture Toughness. . . . . . . . . . . . . . . . . . . . . . . 295
ChaPter 8
Fracture Control and Damage tolerance analysis � � � � � � � � � � � 303
Principles of Fracture Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
Concepts of Damage Tolerance Analysis. . . . . . . . . . . . . . . . . . . . . 307
Fracture Control Measures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Fracture Control Plans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Damage Tolerance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 320
Fracture Mechanics and Fatigue Design . . . . . . . . . . . . . . . . . . . . . 323
ChaPter 9
Fatigue and Fracture of Ceramics and Polymers � � � � � � � � � � � � 327
Ceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
Toughening Ceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
Ceramic Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
Fatigue and Subcritical Crack Growth. . . . . . . . . . . . . . . . . . . . . . . 336
Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
Polymer Fatigue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
Impact Strength and Fracture Toughness. . . . . . . . . . . . . . . . . . . . . 359
Stress Rupture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
Fractography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
Environmental Performance of Plastics. . . . . . . . . . . . . . . . . . . . . . 366
ChaPter 10
Fatigue and Fracture of Continuous-Fiber Polymer-Matrix
Composites � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 377
Laminates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
Composites versus Metallics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
Advantages and Disadvantages of Composite Materials. . . . . . . . . 384
Fatigue Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
Delaminations and Impact Resistance. . . . . . . . . . . . . . . . . . . . . . . 396
Damage Tolerance Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . 401
Effects of Defects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
Building-Block Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
ChaPter 11
high-temperature Failures � � � � � � � � � � � � � � � � � � � � � � � � � � � � 415
The Creep Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
Stress-Rupture Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
Creep Deformation Mechanisms. . . . . . . . . . . . . . . . . . . . . . . . . . . 426
vi / Contents
Elevated-Temperature Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
Metallurgical Instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434
Environmental Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
Creep-Life Prediction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
Design against Creep. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
High-Temperature Fatigue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
ChaPter 12
Wear Failures � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � 461
Abrasive Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462
Erosive Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
Erosion-Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469
Grinding Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472
Gouging Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474
Adhesive Wear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475
Fretting Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479
Contact-Stress Fatigue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481
ChaPter 13
environmentally-Induced Failures� � � � � � � � � � � � � � � � � � � � � � � 501
Basics of Electrochemical Corrosion. . . . . . . . . . . . . . . . . . . . . . . . 501
Forms of Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507
Stress-Corrosion Cracking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521
Hydrogen Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532
Corrosion Fatigue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
Corrosion Prevention. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541
High-Temperature Oxidation and Corrosion. . . . . . . . . . . . . . . . . . 544
ChaPter 14
the Failure analysis Process � � � � � � � � � � � � � � � � � � � � � � � � � � � 549
Collection of Background Data and Samples . . . . . . . . . . . . . . . . . 550
Collecting Data and Samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550
Preliminary Examination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555
Nondestructive Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556
Fracture Origin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559
Selection and Preservation of Fracture Surfaces. . . . . . . . . . . . . . . 561
Macroscopic Examination of Fracture Surfaces . . . . . . . . . . . . . . . 564
Microscopic Examination of Fracture Surfaces. . . . . . . . . . . . . . . . 567
Stress Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567
Fracture Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568
Fracture Mechanics Applied to Failure Analysis. . . . . . . . . . . . . . . 572
Metallographic Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
Mechanical Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575
Contents / vii
Chemical Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579
Simulated Service Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581
A Final Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582
aPPenDIx a
Defects Leading to Failure� � � � � � � � � � � � � � � � � � � � � � � � � � � � � 585
Design Deficiencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585
Material and Manufacturing Defects. . . . . . . . . . . . . . . . . . . . . . . . 588
Ingot-Related Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588
Forging Imperfections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592
Sheet Forming Imperfections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596
Casting Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597
Heat Treating Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
Weld Discontinuities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616
Service-Life Anomalies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624
Materials Selection for Failure Prevention . . . . . . . . . . . . . . . . . . . 627
Index ������������������������������������������������������ 633

Fatigue and Fracture—Understanding the Basics Copyright © 2012 ASM International®
F.C. Campbell, editor All rights reserved
www.asminternational.org
Preface
This book deals with the fatigue and fracture of engineering materials.
Although modern fatigue analysis and fracture mechanics are mathe-
matical disciplines, and mathematical rigor is normally found in texts on
fatigue and fracture mechanics, I have endeavored to construct a more
basic book that balances the major points of fatigue and fracture analysis
without burdening the reader with too much complex mathematical
development.
This book is ideal for the engineer with a basic knowledge of materials
that is just starting to be involved with either failure analysis or fatigue and
fracture analysis. It also provides a sound technical groundwork for fur-
ther study of more advanced texts. This book is useful for the experienced
failure analyst that needs a more thorough background in fatigue and frac-
ture mechanics, or for the fatigue and fracture engineer that needs to know
more about failure modes.
The first chapter gives a high level introduction to fatigue and fracture
and describes some of the noteworthy failures that have occurred during
the industrial age from 1900 to date. As a result of these failures, many of
which were brittle, unexpected, and catastrophic in nature, there have been
numerous changes to design philosophy, and after World War II, the evolu-
tion of fracture mechanics. A number of the life limiting factors are also
introduced, including material defects, manufacturing defects, stress con-
centrations, elevated temperatures, and environmental degradation.
The second chapter covers the basics of the static mechanical properties
of materials. Included are tension, compression, shear, torsion, and com-
bined stress. Both the engineering and true stress-strain curves are covered
in some detail. The importance of stress concentrations and residual
stresses are also included.
The third chapter explains the difference between ductile and brittle
fracture modes from both a macroscopic and microscopic level. The gen-
eral characteristics, the macrostructural and microstructural aspects of
both ductile and brittle fractures are explained. The ductile-to-brittle tran-
ix