Finding Stress-Strain Curve from Load-Deflection Data
Finding Stress-Strain Curve from Load-Deflection Data
(OP)
Hi,
I have the load-deflection data for a composite tube and would like to find the stress-strain curve. I know the dimensions of the tube.
Is it just calculating stress=force/area & strain = change in length/original length at each point from the load-deflection curve or do I have to take anything else into consideration?
Thanks,
David
I have the load-deflection data for a composite tube and would like to find the stress-strain curve. I know the dimensions of the tube.
Is it just calculating stress=force/area & strain = change in length/original length at each point from the load-deflection curve or do I have to take anything else into consideration?
Thanks,
David





RE: Finding Stress-Strain Curve from Load-Deflection Data
Regards,
Cory
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RE: Finding Stress-Strain Curve from Load-Deflection Data
Stress = ( Force * distance to force * distance from neutral axis to force ) / area moment of inertia
Therefore, if you have the force (load data), the cross-sectional measurements, and the distance to the force, then you should be able to retrieve the stress.
From there you know that strain = stress / Young's Modulus.
Assuming you know the modulus for this material, you can find the strain.
Keep in mind, that this is probably only good for the linear elastic region of the material. Afterwards, all bets are off, and the data may take an odd turn.
V
Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."
- R. Buckminster Fuller
RE: Finding Stress-Strain Curve from Load-Deflection Data
Thanks,
David
RE: Finding Stress-Strain Curve from Load-Deflection Data
V
Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."
- R. Buckminster Fuller
RE: Finding Stress-Strain Curve from Load-Deflection Data
i don't think it's relevant for your case, but rememebr poisson's effect (affecting the area).
did you measure the change in diameter of the test piece ? i suspect that the sides of your tube might have bowed outwards, affecting your results (if you were trying to charactise the material).
RE: Finding Stress-Strain Curve from Load-Deflection Data
The load-deflection curve was obtained from a reference standard handbook so even though there must have been some bowing, I do not know the values of the out of plane deformations (poisson's effect).
RE: Finding Stress-Strain Curve from Load-Deflection Data
poisson accounts to the thickness change (like the necking of a tension test specimen) ... i don't think it a pplies in this particular case, i mentioned it just in case you were going onto other things.
but if you've got a load/deflection curve from a standard reference, then i'd divide the loa by the area, and the deflection by the original length of the specimen. (like your OP!)