Back-calculating strain in tooling
Back-calculating strain in tooling
(OP)
I am currently testing a composite coupon in tension. I am using the crosshead displacement for the extension - I have no means to attach extensometers or strain gauges.
The problem is, I know that a part of the tooling is adding to the strain. If I can work out the elastic modulus of the tooling, is there an equation to deduct its strain from the total extension measured by the tensile testing machine?
Cheers,
Dave
The problem is, I know that a part of the tooling is adding to the strain. If I can work out the elastic modulus of the tooling, is there an equation to deduct its strain from the total extension measured by the tensile testing machine?
Cheers,
Dave





RE: Back-calculating strain in tooling
RE: Back-calculating strain in tooling
I just wondered if there was an equation you could apply if you knew the material characteristics of the tooling (or studding in this case).
Cheers,
Dave
RE: Back-calculating strain in tooling
You could come up with free body diagrams and constitutive equations for each member of the load train and create an equation. Or, you can eliminate (or substitute) the specimen and run a test to measure the combined elastic and plastic strains in the load train, then use those results to create the equation. Both have difficulties.
RE: Back-calculating strain in tooling
I appreciate that the whole system is straining, but the load is about 3Kn, not much, and the threaded bar is the obvious weak point. The other parts of the tooling are massive in comparison.
I have pulled a piece of the threaded bar on it's own. It yielded at around 3.5Kn, so I'm pretty certain it's in an elastic phase.
Can I use those results to create an equation? And if so, what's the equation!?
Thanks for your help so far,
Dave
RE: Back-calculating strain in tooling
RE: Back-calculating strain in tooling
I didn't know if you could just do a straight subtraction of the bar's force/displacement over 3Kn from the total force/displacement of the bar and sample over 3Kn, but that seems to be what your equation is inferring. Sometimes I'm wary over the obvious, simple solutions, but if you're backing it then I'll go with it!
Cheers, take it easy.
Dave