The parameter calibration of CpmMat

Hello,

But I do not know the reasonable range of the per microscope parameter. Can
> you give me suggestions?

For a set of reasonable parameters, see e.g. yade/examples/concrete, for
instance uniax.py [1]. What is "reasonable range" is difficult to say and
depends very much on your material and situation where you want to use the
model :-)

And I also want to know if any of these parameters (young, sigmaT,
> relDuctility, poisson, frictionAngle, epsCrackOnset) have conversion
> formula to experiment parameter.

unfortunatelly no, you have to use some kind of optimization to find values
such that the macroscopic response match your requirements.

> For example, does the parameter ”young” equal to macroscopic Young’s
> moduli in experiment or not. I do not understand the statement “In our
> case, however, we simply run elastic simulation to determine the actual
> E/kN ratio (3.40). To obtain desired macroscopic modulus of E∗, the value
> of kN is scaled by E∗/E.”

young parameter equal normal modulus E of bonds represented as rods
(considering their crossection is A=pi*r*r) in formula F = k*u = (EA/L)*u,
L being distance of particles and u their mutual displacement
(penetrationDepth). The resulting macroscopic modulus depends on how
"dense" is your interaction network. However, for the same network, the
micro and macro moduli are proportional, it is the meaning of the second
part of the paragraph. If you double micro modulus, you will get double
macro modulus. So you can set the correct young value from one simulation
(knowing the ratio of resulting and desired macro modulus).

All the other input parameters does not behave so nicely :-)

A standard approach would be firstly determine elastic parameters (young,
poisson), which are independent on inelasticity. Then determine the
inelastic parameters (using fixed young and poisson). For calibration, also
consider using the dimensional analysis mentioned in [2] from your previous
message.

cheers
Jan

[1] https://github.com/yade/trunk/blob/master/examples/concrete/uniax.py

2016-08-02 17:57 GMT+02:00 liukeqi <email address hidden>:

> New question #315620 on Yade:
> https://answers.launchpad.net/yade/+question/315620
>
> Hello,
>
> I want to calibrate microscope parameters to simulate the
> stress-strain curve of concrete obtained by experiment in the reference[1].
> But I do not know the reasonable range of the per microscope parameter. Can
> you give me suggestions?
>
> And I also want to know if any of these parameters (young, sigmaT,
> relDuctility, poisson, frictionAngle, epsCrackOnset) have conversion
> formula to experiment parameter. For example, does the parameter ”young”
> equal to macroscopic Young’s moduli in experiment or not. I do not
> understand the statement “In our case, however, we simply run elastic
> simulation to determine the actual E/kN ratio (3.40). To obtain desired
> macroscopic modulus of E∗, the value of kN is scaled by E∗/E.” in the page
> 52 of reference[2]. If it means that the young parameter in CpmMat do not
> equal to the Young in experiment.
>
> Thank you.
>
> [1] http://link.springer.com/article/10.1007/BF02476284
> [2] https://tel.archives-ouvertes.fr/tel-00502402/
>
>
>
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Thanks Jan Stránský. It solved my problem. Sorry for the late reply. I just come back from the 7th International Conference on Discrete Element Method.