Machine Design_slide 8

Machine Design_slide 8 - ENGR3220MachineDesign...

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ENGR 3220 – Machine Design ENGR 3220 – Machine Design Week 5, Lecture 1 Week 5, Lecture 1 Fatigue Failure Fatigue Failure
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Fatigue Failure Machine members are found to have failed under the action of repeated or fluctuating stresses even the actual maximum stresses were well below the ultimate strength of the material or even below the yield strength. The most distinguishing characteristic of these failures is that the stresses have been repeated a very large number of times , these failures are called fatigue failures . Fatigue failure is due to crack formation and propagation . A fatigue crack will initiate at a discontinuity in the material where cyclic stress is a maximum. Various conditions that accelerate crack initiation include residual tensile stresses, elevated temperatures, temperature cycling, a corrosive environment, and high-frequency cycling.
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Fatigue Failure Fatigue failure has three stages of development: Stage I : initiation: one or more cracks Stage II : propagation: from microcracks to macrocracks Stage III : fast fracture Fatigue failure of a bolt due to repeated unidirectional bending.
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This note was uploaded on 04/16/2011 for the course ENGR 3220 taught by Professor Turro during the Spring '11 term at UOIT.

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Machine Design_slide 8 - ENGR3220MachineDesign...

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