Tensile test and Poisson ratio calibration

[ctrlc0ctrlv]

Hi everyone,

In my research I am trying to simulate an epoxy (Poisson ratio of epoxy is about 0,3 and Young modulus = 3 GPa). So during calibration with tensile test I faced a problem: axial Poisson's ratios Poisson_YY and Poisson_ZZ are too different.

poisson_graph.png

Is it correct to use average Poisson ratio for calibration (Poisson_ave on picture) or am doing something wrong?

Test sample is a cube box 7*7*7mm with AverageDeRadius="227e-6" and RandomRange="25%", so Cardinality is about 6,2 and ratio "microscale over macroscale" is more than recommended 20.

Here are parts of my input file (TimeStep="3e-8" and there are 300000 iterations):
         <PlugIn Id="_Convert" What="ElementPair" To="Beam" YoungModulus="501.5e9" RadiusRatio="0.1557" PoissonRatio="0.3" />
...
        <PlugIn Id="_ImposeDisplacement" Clamp="true" Set="Boundary-xMin" />
        <PlugIn Id="_ImposeDisplacement" X="0.1e-7*it" Y="0" Z="0" Set="Boundary-xMax" TriggerIf="it<3000" />
        <PlugIn Id="_ImposeDisplacement" X="3e-5" Y="0" Z="0" Set="Boundary-xMax" TriggerIf="it>=3000" />

Also, I don't use _SetElasticProperty plugin, because it gives me wrong values (it gave me MicroYoungModulus = 83 GPa and RadiusRatio = 0,32 for CoordinationNumber = 6,183722 for the values of the macroparameters specified at the beginning) Is it OK? And is the calibration procedure that I use in general normal?

Thanks

[Damien André]

Hello,

ctrlc0ctrlv wrote

In my research I am trying to simulate an epoxy (Poisson ratio of epoxy is about 0,3 and Young modulus = 3 GPa). So during calibration with tensile test I faced a problem: axial Poisson's ratios Poisson_YY and Poisson_ZZ are too different.

Is it correct to use average Poisson ratio for calibration (Poisson_ave on picture) or am doing something wrong?

I guess that you can improve the accuracy of your results by unclamping the "Boundary-xMin" set. The discrete element must be free to move in the Y and Z direction to match a perfect uniaxial tensile test.

Kind regards, Damien.

[ctrlc0ctrlv]

Thanks for your reply
Should I also do similar thing to "Boundary-xMax"? I mean this:

<PlugIn Id="_ImposeDisplacement" X="0.1e-7*it" Set="Boundary-xMax" TriggerIf="it<3000" />

[Damien André]

ctrlc0ctrlv wrote

Thanks for your reply
Should I also do similar thing to "Boundary-xMax"? I mean this:

<PlugIn Id="_ImposeDisplacement" X="0.1e-7*it" Set="Boundary-xMax" TriggerIf="it<3000" />

Yes ;-) Of course !