Quote:
Originally Posted by mr beer
When does that start happening?
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For ductile metals like steel and aluminum, at about a few hundred nanometers (this is the radius over which ductile deformation is happening at the crack tip. For plastics it is more like a few tens to hundreds of microns. For glass, it really is all happening at only an atom or two in radius.
For a rough dimensional analysis of the distance over which the strain is occurring around the crack tip, divide the strain energy release rate by Young's modulus (you can look up both of these quantities for most commonly used materials).
Luke