Metal Fatigue

263 Pages·1974·11.3 MB·263\263

by  Frost, N.E., Marsh, K.J., Pook, L.P.

METAL
FATIGUE
N. E. Frost
K.1. Marsh
and
L. ~ Pook
DOVER PUBLICATIONS, INC.
Mineola, New York
Copyright
Copyright© 1974byOxford UniversityPress
New Preface to the Dover Edition copyright © 1999by N. E. Frost,
K.1.Marsh, and L. P.Pook
Allrights reserved.
BibliographicalNote
This Dover edition, first published in 1999,isan unabridged republi
cation of the work originally published in the "Oxford Engineering
ScienceSeries"byClarendonPress,Oxford,in1974.AnewPrefacetothe
DoverEdition hasbeenspeciallyprepared forthepresentedition. Offset
fromtheOxfordUniversityPresseditionofMetalFatiguebyN.E.Frost,
K.1.Marsh and L. P.Pook.
LibraryofCongressCataloging-in-Publication Data
Frost, N.E.(NormanEdward), 1923-
Metal fatigueIN.E. Frost, K.1.Marsh, and L.P.Pook.
p.em.
Originally published: Oxford, Eng. : Clarendon Press, c1974, in
series:Oxfordengineeringscienceseries.
Includesbibliographical referencesand index.
ISBN0-486-40927-9(pbk.)
1. Metals-Fatigue. I. Marsh, K. 1. (Kenneth James), 1935
II. Pook,L. P.(LesliePhilip), 1935-III. Title.
TA460.F76 1999
620.1'66-dc2I
99-048936
ManufacturedintheUnited Statesby CourierCorporation
40927902
www.doverpublications.com
Preface to the Dover Edition
Thisbook, published 25yearsago,signalledsomethingof aturningpoint
in the literature ofmetal fatigue. Not only does it include a comprehen
sivecollection of fatigue data published up to the early 1970s,but it was
also thefirstmonograph to stressthe importanceof fatiguecrack propa
gation in the interpretation of the fatigue phenomenon. This approach
wascarried out within the then novel(but nowubiquitous)framework of
linearelasticfracture mechanics.Similarly,itwasthefirstbookonfatigue
to bewritten inSIunits.Thefatiguetestingof componentsand structures
under realistic variable-amplitude simulations of service loading condi
tions, using the then recentlyavailableservo-hydraulic testing equipment
is described. This is a field in which considerable advances have been
made,particularlythewidespreadstandardizationof testand designtech
niques, and the advent of undreamt-of computing power. However,
despite the technological advances made in the past 25 years the basic
concepts of metal fatiguepresented inthe book arestillsound.
January 1999
Cambridge N.E.F.
Carlisle K. 1.M.
Sevenoaks L. P. P.
Contents
1. INTRODUCTION 1
References 5
2. CRACK INITIATION 6
2.1. Introduction 6
2.2. Surfaceexamination 7
2.3. Changesinbulkproperties 17
2.3.1. Hysteresisloopand dampingmeasurements 17
2.3.2. Changesinmechanicalproperties,stiffness, hardness,etc. 18
2.3.3. Changesinphysicalproperties 20
2.3.4. Strain-ageing effects: coaxing, rest-periods, intermittent
heat-treatments 20
2.3.5. Diffusionand surfaceemissionstudies 23
2.3.6. X-raydiffractionstudies 24
2.4. Discussionofsurfacecrackinitiation 25
References 35
3. FATIGUESTRENGTH OF PLAIN SPECIMENS 40
3.1. Introduction 40
3.2. Thefatiguelimit,orfatiguestrengthat longendurances 40
3.3. Effectofsurfacefinish 48
3.3.1. Method ofmachining 49
3.3.2. Effectofelectropolishing 50
3.3.3. Effectofstress-relieving 51
3.3.4. Effectofforgedsurfaces 52
3.3.5. Discussion 52
3.4. Differenttestingmethodsand sizeeffects 54
3.4.1 Discussion 61
3.5. Effectofa meanstress 65
3.5.1. Discussion 74
3.6. Effectofcombinedstressesand anisotropy 75
3.6.1. Discussion 85
3.7. Effectof frequencyofstressapplication 87
viii Contents
3.8. Effectof temperature 90
3.8.1. Low-temperature fatigue 91
3.8.2. Elevated-temperaturefatigue 92
3.8.3. Thermalfatigue 101
3.8.4. Discussion 103
3.9. Effectofenvironment 105
3.9.1. Mechanismofcorrosion fatigue 107
3.9.2. Fatiguestrength inwaterand brine 109
3.9.3. Effectofhumidity 112
3.9.4. Protectivemeasures 113
3.9.5. Exclusionof theatmosphere 115
3.9.6. Discussion 119
References 122
4. EFFECT OF STRESS CONCENTRATIONS AND CRACKS
ON FATIGUE STRENGTH 130
4.1. Introduction 130
4.2. Elasticstressdistribution around a notch 133
4.3. Behaviourofnotched laboratoryspecimensat zeromeanload 136
4.3.1. Experimentaldata 136
4.3.2. Kt-K relationships 143
t
4.4. Non-propagatingcracks in notchedspecimens 149
4.5. Theminimumalternatingstressrequired to propagate a crackofa
givenlengthor depth at zeromeanstress 157
4.5.1. Testson specimenscontaining artificialcracks 157
4.5.2. Testsonplain specimenscontaining fatiguecracks 157
4.5.3. Testsonspecimenscontaining fatiguecracksgrownat
notches 159
4.5.4. Tests to determine the relationship between crack length
and the stress necessaryfor crack growth 160
4.6. Interpretation ofzero mean load notched fatigue data 166
4.6.1. Wrought materials 166
4.6.2. Castmaterials 173
4.7. Effectofa meanload 175
4.7.1. Notched specimens 175
4.7.2. Crackedspecimens 180
4.8. Effectofcombinedstresses 184
4.9. Effectoftemperature 187
4.10. Effectofenvironment 188
4.11. Additional implicationsofa macrocrack length-cyclicpropagation
stressrelationship 195
Contents ix
Fleferences 198
5. THE GFlOWTH OF FATIGUE CFlACKS 202
5.1. Introduction 203
5.2. Linearelasticfracture mechanics 205
5.2.1. Modesofcrackgrowth 205
5.2.2. Stressintensityfactor 206
5.2.3. Crack direction 210
5.2.4. Effectofyielding 210
5.2.5. Applicationto fatiguecrackgrowth 211
5.3. Fractographicaspectsofcrackgrowth 213
5.3.1. Macroscopicappearance 213
5.3.2. Crack direction 213
5.3.3. Microscopicappearance 216
5.4. Metalphysicsaspectsofcrackgrowth 220
5.5. Determinationoffatiguecrackgrowth rates 222
5.6. Somefatiguecrackgrowth theories 228
5.6.1. Head's theory 228
5.6.2. Thegeometricalsimilarityhypothesis 229
5.6.3. Net area stresstheories 231
5.6.4. Accumulatedstrain hypothesis 233
5.6.5. Dislocation theories 234
5.6.6. Energytheories 235
5.6.7. Frostand Dixon's theory 235
5.6.8. Afracture-mechanicscrackgrowth theory 238
5.6.9. Correlation withexperiment 239
5.7. Fatiguecrack growthdata for various materials 245
5.8. Thresholdeffectsinfatiguecrackgrowth 260
5.9. Other factors affectingcrackgrowth 263
5.9.1. Effectofthickness 263
5.9.2. Effectoftestfrequency 264
5.9.3. Effectofloadchanges 265
5.9.4. Effectofenvironment 266
5.9.5. Effectofstressstate 269
5.9.6. Methods ofincreasingresistanceto fatiguecrack growth 272
5.10. Fatiguecracksinstructures 275
5.10.1. Residualstaticstrength ofcrackedstructures 275
5.10.2. Estimation ofservicelife 283
References 285
x Contents
6. NOTES ON VARIOUS OTHER ASPECTS OF FATIGUE 293
6.1. Low-endurancefatigue 293
6.1.1. Introduction 293
6.1.2. Total strain amplitude tests 295
6.1.3. Plasticstrain amplitude tests 297
6.1.4. Mode offracture and the effectof meanstrain 300
6.1.5. Notched specimens 302
6.1.6. Discussion 304
6.2. Fatigue under varyingstressamplitudes 307
6.2.1. Introduction 307
6.2.2. ThePalmgren-Minerruleand earlyexperimentalwork 308
6.2.3. Other prediction methods 311
6.2.4. Programme loadingto simulateserviceconditions 318
6.2.5. Random loading 321
6.2.6. Servo-hydraulictestingmethods 325
6.2.7. Structural fatiguetestson vehicles 327
6.2.8. Acceleratedtesting 328
6.2.9. Discussion 329
6.3. Effectofmechanicalworking 330
6.3.1. Introduction 330
6.3.2. Effectofwork-hardening 331
6.3.3. Effectofresidualstresses 332
6.3.4. Discussion 337
6.4. Surfacetreatments 340
6.4.1. Metalplatings 340
6.4.2. Anodizing 346
6.4.3. Metallurgicalsurface-hardeningtechniques 347
6.4.4. Softlayers 352
6.5. Pressurizedcylinders 353
6.6. Fretting 364
6.7. Pin, riveted,and boltedjoints 370
6.7.1. Pinjoints 370
6.7.2. Rivetedand boltedjoints 375
6.8. Weldedjoints 379
6.8.1. Introduction 379
6.8.2. Butt weldsinstructuralsteels 379
6.8.3. Filletweldsinstructuralsteels 385
6.8.4. Butt weldsinlightalloys 390
Contents xi
6.8.5. Methods ofimprovingfatiguestrength 391
6.8.6. Spot welds 392
6.8.7. Glued, brazed,and pressure-weldedjoints 395
6.9. Shrink-fitassemblies 397
6.10. Screwedconnections 401
6.11. Rollingcontact 408
6.12. Methodsofrapidlyestimatingthefatiguelimitofamaterial 410
6.13. Statisticalanalysisoffatigue testresults 417
6.13.1.Introduction 417
6.13.2. Applications to SINcurves 418
6.13.3. Combined distributions 422
6.13.4. Testmethods basedon statisticaltheory 424
6.14. Fabricatedmaterials 427
6.15. Components and structures 429
References 436
APPENDIX 1. TERMS USED INDEFINING THE STRESS-STRAIN
RELATIONSHIPS OF A MATERIAL 455
References 457
APPENDIX2 REPEATED LOADING AND FRACTURE 458
References 459
APPENDIX3. COMPARISON OF APPEARANCES OF BROKEN
TENSILE AND FATIGUE SPECIMENS 460
APPENDIX 4. ELEMENTARY CONCEPTS OF PLASTIC DEFOR-
MATION IN DUCTILE METALS 461
References 463
APPENDIX 5. FATIGUE TESTING MACHINES 464
A5.I. Conventional direct-stressmachines 465
AS.2. Servo-hydraulicmachines 466
A5.3. Other machines 466
~re~ces 4~
APPENDIX 6. TEST SPECIMENS AND METHODS FOR DETER-
MINATION OF PLAIN FATIGUE PROPERTIES 469
A6.1. Specimens 469
A6.2. Testingand presentation ofresults 471
References 475
xii Contents
APPENDIX 7. STRESS CONCENTRATION FACTORS FOR VAR-
IOUS CONFIGURATIONS 476
References 480
AUTHOR INDEX 481
SUBJECT INDEX 493
ILLUSTRATIONS
Thefollowinglistoffiguresappearasseparateplate sections.
FIG. 2.1. FIG. 5.4. FIG. 6.44.
2.2. 5.5. A3.I.
2.3. 5.6. A3.2.
2.4. 5.7. A5.I.
2.5. between 5.8. between A5.2. between
2.6. pp. 12-13 5.10. pp. 212-13 A5.3. pp. 460-1
2.7. 5.11. A5.4.
4.10. 5.12. A5.5.
4.11. 6.14. A5.6.
4.19. 6.18.
4.23. 6.23.
[J]
I
Introduction
MATERIALS, whether they be metallic or non-metallic, are of nopractical
usetomankinduntiltheyareturnedinto workingcomponentsor structures.
One link in the process chain by which this happens is called engineering
design.
A major problem facingthe designeristhe selectionofthe right materials
fromwhichtomanufactureaparticulardesignofcomponentorstructure;the
material properties mustensure that itcarries out the dutiesfor whichitwas
designedwithoutbreakingwithinaguaranteedlifeandyetenableittobesold
atapricewhichthecustomerispreparedtopay.Toenablehimto do this, the
designer needs to know the loads to which his componentor structurewill
be subjected in service,the environmentin which it willwork, the working
life expected, and what it will cost to make. This information now sets
boundaries on the range of materials from which to select those to use for
hisspecificdesign.To finalizethechoiceofmaterials, heneedsto knowhow
they behave under various loadings in various environments (that is, the
material properties), and then, knowingtheseproperties, he must beable to
correlate them with the load-carrying capacity of his proposed component
orstructure. Thesubjectsofstressanalysisand fracture mechanicshavebeen
developedexclusivelyfor this purpose.
However, a number of indeterminate factors arise: the loading to be ex
perienced by the component or structure in service is often known only
imprecisely, manufacturing and fabrication techniques may induce residual
stresseswhosemagnitudesare unknownat thedesignstage, the actualgeom
etryinsomelocalregionmaydeviatefrom thatstipulatedon the drawing so
thatthe originalstressanalysismaybeinerror, or the properties ofthe ma
terial used in manufacture may be different from those assumed by the
designer.Thus, experiencein bothchoiceofmaterial andallowable working
stresses for any common grouping of various types of components and
structuresisall-importantin achievinga successfulend-product.
Traditional design was based on the concept of a factor of safety (to
supposedly cover all unknown and imprecisely known factors), the tensile
strength of the material, and a nominal stress analysis procedure. This, of
course, was the only approach possible when little was known ofmaterial
properties, fracture mechanisms, detailed stress analysis, and serviceload
ings. The factor of safety used wasgenerally a matter of personal intuition