Quote:
Originally posted by WinFlex
You do however bring up a valid point. WE NEED TO FIND THE CRACK TIP ENERGY for polycarbs in order to continue this analysis on a scientific basis.
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You'd be better off with a crack growth rate, I think. I have one for an "average" acrylic - only an example graph, no specs on the material.
How about fracture toughness?
I have data on a sample polycarbonate with a fracture tougness of 3,000 psi -inch^(1/2). Yield stress is 8400 psi.
I don't have the geometry factor for radial flaws, unfortunately, so someone more skilled in mechanics should take it from there. If I spoke any further on this, I fear BillA might set my house on fire.
/me yells "What's that!" at BillA so he looks away and doesn't read the next paragraph.
What you really want, I think, is a crack growth rate. Assume for a second the forces are enough to lead to some crack propogation, and that flaws are already present. You know that there is a cycle of stress on the material as it heats up and cools down. This can tell you how long until some sort of failure occurs. If the forces are far too low or far too high for slow crack growth, it will be obvious at this point. You also need to know a coefficient of thermal expansion and stress-strain curve to find out what that cyclic stress is, as well as the size of any intial cracks.
Most of my knowledge is in fluid deformation rather than solid deformation, so that's all I got. Just be lucky you're dealing with unidirectional stresses.
Alchemy