reference/textbook for theory behind VIII-1 impact testing exemptions 2

[keyen]

I'm curious about the theory behind the impact testing exemptions permitted in VIII-1. Specifically:

1. Why are thin plates exempt to lower temperatures than thick plates?
2. Why is the effective thickness of plate stress in bending one-quarter of the actual thickness when determining the minimum impact exemption temperature?

Can both of the above questions be answered with classic fracture mechanics theory?

Can anyone point me to a reference textbook or white paper(s) that explains the theory behind these rules?

 

[pdiculous963]

The background to the VIII-1 rules is documented in Annex A of WRC Bulletin 528. They were originally developed by Corten using a fracture mechanics basis.

On your question, toughness is not actually a material property as it can vary based on thickness. Thick components tend to have higher constraint than thinner components and are more susceptible to fracture. Corten's paper uses a 1/4 thickness flaw depth to develop the exemption curves, so the postulated flaws used in the fracture mechanics assessment are larger for thicker plates.

 

[metengr]

Lets not confuse impact energy behavior with fracture toughness. In materials science, fracture toughness is a material property. You can measure K [sub]Ic[/sub] stress intensity factor (elastic fracture behavior ) and J[sub]Ic[/sub] which is elastic-plastic fracture behavior.