I have data obtained from compression test. how to calculate young modulus from a compression test (stress-strain curve) with nonlinear elastic region?
Hello,
In my case, I used an optimization tool to identify nonlinear parameters that fit the compression experiment results.
However, Young's modulus is a property of the linear elastic region. In the nonlinear region, it is necessary to select a nonlinear constitutive law according to the purpose and determine its parameters.
There is no young modulus in non linear elastic region, it can calculated just from elastic region, because it is the slope between stress and strain …..
Question is incomplete. What kind of material it is ? Ductile, Brittle, Plastic, strain hardening, strain softening, etc..... For the drooping portion of the curve, the instantaneous modulus will change from positive to negative value, after the peak. Slope of this line indicates, how fast material is degrading. E can be estimated continuously between two succesive points on the curve. This is used for non-linear analysis, as input.
I agree with Kawashima's answer and supplement here. Nonlinear constitutive laws are important to model the material for analysis beyound lienar range. It also need input for confinement of material, whether the test data is from uniaxial loading without lateral confinement, or there is a confining pressure. Depending on this pressure, material behaviour will change drastically. As I said, failure theories based on type of material are also important, to take the 'E' value, and model in any computational tool. I can say, the classic GIGO > 'Garbage In and Garbage Out' for any computational tool. But, I revised this as, 'Gold In and Gold Out', based on my experience with CAD, CAE and FEM Tools. If the input is perfect, out out will be perfect, provided the tool is good, vefied and validated.
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