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[Austin Sutton <question672563@xxxxxxxxxxxxxxxxxxxxx>]

Question #672563 on Yade changed:
https://answers.launchpad.net/yade/+question/672563

    Status: Answered => Open

Austin Sutton is still having a problem:
*Luc,* I appreciate your effort in putting together that script. It is
long, but it I'm grateful since it provides a lot of details that I was
going to need to figure out anyways. Thanks!

--> In my mind, the biperiodic configuration where the sample is sandwiched in
between 2 moving plates corresponds to a direct shear test... It does,
right?
After reading a bit more into the topic, it seems that it is simple shear.
However, the script you made is still useful since I've read that direct
and simple shear tests have been shown to provide close results in terms of
steady-state stress for some materials. In other words, they may differ in
terms of peak stress and strain, but can give the same yield locus curves.

*Bruno,* thank you for your input.

--> They are fundamentally different I'm afraid. Even direct and rotational
are not the same.
This is exactly what I was thinking, but wasn't entirely sure. Thank you
for the clarification.

-->  The yade's preprocessor "SimpleShear" is badly named, btw, since it
simulates a direct shear.
I had no idea. I dismissed this route because of its name...thank you for
bringing this to my attention.

*To all,* thanks for your input. I believe I have a couple of different
routes to try. One last question: have either of you heard of reducing the
modulus of the powder material in a simulated shear cell to reduce
computational time? I'm just wondering since my material is small stainless
steel particles: high modulus with a minimum particle size of 1 um == very
small timestep. Since we care about stresses, I'm wondering if this would
be frowned upon. If I were to reduce the modulus, I believe I would just
need to ensure that the volume ratio of the packing when initially
consolidated is the same as that observed experimentally.


On Fri, Aug 31, 2018 at 10:43 AM, Bruno Chareyre <
question672563@xxxxxxxxxxxxxxxxxxxxx> wrote:

> Your question #672563 on Yade changed:
> https://answers.launchpad.net/yade/+question/672563
>
> Bruno Chareyre proposed the following answer:
> >the biperiodic configuration where the sample is sandwiched in between
> 2 moving plates corresponds to a direct shear test...
>
> Direct shear refers to the (inhomogeneous) shear box for soils, or a
> sheared rock joint.
> The yade's preprocessor "SimpleShear" is badly named, btw, since it
> simulates a direct shear.
> Rotational shear is not homogeneous, although it does not impose the
> position of the shear band as firmly as direct shear.
>
> Conversely, the periodic BCs define simple shear (homogeneous). Only
> very specific devices (e.g. 1γ2ε in Grenoble) can do such thing in
> practice.
>
> >  you could try to apply a rotation to the top plate with the centre of
> rotation located either the centre of the sample or offset from it so as
> to mimic your experiment...
>
> Nope. Such a rotational field is not periodic, the simulation would just
> go weird. It is not possible to use periodic BCs for rotational shear
> (unless someone implements periodicity for annular geometries, which is
> not straightforward).
>
> Bruno
>
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-- 
*Austin Sutton*
Graduate Research Assistant and Graduate Teaching Assistant
342 Toomey Hall, Rolla, MO 65409
PhD Student - Mechanical Engineering Department
Missouri University of Science and Technology

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