chapter 6 - outline machine element design i
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Fatigue failure resulting from variable loading
By
Soheil Nakhodchi
Machine Element Design I
K.N.Toosi University of Technology
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Chapter 6 - Outline
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6–1 Introduction to fatigue in metals
6–2 Approach to fatigue failure in analysis and design
6–3 Fatigue life methods
6–4 The stress-life method
6–5 The strain-life method
6–6 Linear elastic fracture mechanics method
6–7 The endurance limit
6–8 Fatigue strength
6–9 Endurance limit modifying factor
6–10 Characterizing fluctuating stresses
6–11 Torsional fatigue stress strength under fluctuating stress
6–12 Combination of loading modes
6–13 varying, fluctuating stress, cumulative fatigue damage
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Introduction to fatigue in metals Introduction to fatigue in metals
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Figure 6.1- Fatigue failure of a bolt due to repeated unidirectional bending.
Failure started at thread root A, propagated across most of cross section shown by beach marks before final fast fracture at C
Three stages of fatigue failure Initiation Propagation Final fracture
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Introduction to fatigue in metals
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“ASM Handbook, Fractography, Vol.12” is a good reference for learning failure surfaces.
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Introduction to fatigue in metals
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Approaches to fatigue failure in analysis and design
• The stress-life methods
• The strain-life methods
• The linear elastic fracture mechanics
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Stress-Life approach
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R. R. Moore rotating-beam fatigue testing machine
Stress-Life approach
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Stress-Life approach
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Stress-Life approach
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Stress-Life approach