"Ned Simmons" wrote in message
...
On Thu, 23 Feb 2012 20:11:33 -0500, "Jim Wilkins"
wrote:

I agree with your conclusion, but the .2% number you used to get
there
has nothing to do with elastic deformation, and it's only a
coincidence that our numbers are close. I could just as easily have
used .1 in^2 as the area in my example, and the resulting strain
would
be 10mm per meter.

I suspect the practical limitations of tensile testing machines 100
years ago is why the transition from elastic to plastic was
designated
at .2% elongation. In other words, that's what could be reliably
detected.
Ned Simmons

I should have written 30E3 PSI, not total stress. 300KSI material is
beyond my machining and heat-treating ability so its superior
elongation doesn't help for homebrew load cells.

I operated one of those old Tinius Olsen tensile strength machines in
a test lab and agree with you. It was kind of tricky to get good
repeatable results from it.

jsw