Budynas-Nisbett:Shigley's Il.Failure Prevention 6.Fatigue Failure Resulting ©The McGraw-Hill Mechanical Engineering from Variable Loading Companies,2008 Design,Eighth Edition Fatigue Failure Resulting from Variable Loading 261 maximum tensile stresses.The crack growth process can be explained by fracture mechanics (see Sec.6-6). A major reference source in the study of fatigue failure is the 21-volume ASM Metals Handbook.Figures 6-1 to 6-8,reproduced with permission from ASM International,are but a minuscule sample of examples of fatigue failures for a great variety of conditions included in the handbook.Comparing Fig.6-3 with Fig.6-2,we see that failure occurred by rotating bending stresses,with the direction of rotation being clockwise with respect to the view and with a mild stress concentration and low nominal stress. Figure 6-3 Fatigue fracture of an AlSl 4320 drive shaft.The fatigue failure initiated at the end of the keyway at points B and progressed to final rupture at C.The final rupture zone is small,indicating that loads were low.(From ASM Handbook,Vol.11:Failure Analysis and Prevention,ASM International,Materials Park. OH440730002,fig18, p.111.Reprinted by permission of ASM International www.asminternational.org.) Figure 6-4 Fatigue fracture surface of an AISI 8640 pin.Sharp corners of the mismatched grease holes provided stress concentrations that initiated two fatigue cracks indicated by the arrows.(From ASM Handbook,Vol.12: Fractography,ASM International,Materials Park, OH440730002,fig520, p.331.Reprinted by permission of ASM International www.asminternational.org.]Budynas−Nisbett: Shigley’s Mechanical Engineering Design, Eighth Edition II. Failure Prevention 6. Fatigue Failure Resulting from Variable Loading 264 © The McGraw−Hill Companies, 2008 Fatigue Failure Resulting from Variable Loading 261 Figure 6–3 Fatigue fracture of an AISI 4320 drive shaft. The fatigue failure initiated at the end of the keyway at points B and progressed to final rupture at C. The final rupture zone is small, indicating that loads were low. (From ASM Handbook, Vol. 11: Failure Analysis and Prevention, ASM International, Materials Park, OH 44073-0002, fig 18, p. 111. Reprinted by permission of ASM International ®, www.asminternational.org.) Figure 6–4 Fatigue fracture surface of an AISI 8640 pin. Sharp corners of the mismatched grease holes provided stress concentrations that initiated two fatigue cracks indicated by the arrows. (From ASM Handbook, Vol. 12: Fractography, ASM International, Materials Park, OH 44073-0002, fig 520, p. 331. Reprinted by permission of ASM International ®, www.asminternational.org.) maximum tensile stresses. The crack growth process can be explained by fracture mechanics (see Sec. 6–6). A major reference source in the study of fatigue failure is the 21-volume ASM Metals Handbook. Figures 6–1 to 6–8, reproduced with permission from ASM International, are but a minuscule sample of examples of fatigue failures for a great variety of conditions included in the handbook. Comparing Fig. 6–3 with Fig. 6–2, we see that failure occurred by rotating bending stresses, with the direction of rotation being clockwise with respect to the view and with a mild stress concentration and low nominal stress