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| Failure Mechanisms | |||||||||||||||||
| ·
Consider
either the surface crack of length a, or the bulk crack of length 2a shown.
· If no net change in system energy results from critical crack propagation: {Increase in Surface Energy } = {Decrease in Strain Energy}. · The surface energy of the crack, US,is given by: US= 2(2aS) = 4aS i.e. (dUS/da) = 4S |
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| From:
Callister, "Materials Science and Engineering,"
Wiley (1994) |
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| · The Elastic strain energy released in the presence of a crack of length 2a is: UE = π(1- ν2)a2 σ2/E i.e: dUE/da = 2πa(1 - ν2)σ2 /E . | |||||||||||||||||