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Simple Tensile Test
Posted Nov 16, 2017, 1:16 p.m. EST Structural & Acoustics, Geometry, Materials Version 5.2a 5 Replies
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Hopefully the fix can easily be managed. I am working with a 1mm^3 cube and want to back out a poisson ratio after applying a known displacement.
Property values include Young Modulus (3000 MPa), density 1380 (kg/m^3), and poisson ratio (.4).
I am applying a displacement of 1% (to one side, the other opposite side cannot move in the x direction). In the Y directions, the faces can only move in the Y and X direction while in the Z direction it can only move in the X and Z directions.
The most dense mesh I have used is on the order of 100000 elements with element qualities of 1 (I am using cubes).
My issue is that the displacments in the Y and Z directions provide maximum displacements that would back out a poisson ratio with error on the order of 10-15%. As this is a simple unit problem it should be closer to 1%. What common issues might be responsible for the skew?
Attachments:
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Your BCs are suspicious. I am not familiar with an analytical solution for the problem as you set it up. Perhaps you meant to set up the model as attached. Even with a much coarser mesh (a single element!), you can "back out" a Poisson ratio of .4 with accuracy of 14 decimal places, i.e. numerical noise.
Jeff
-------------------Jeff Hiller
Attachments:
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Thanks for the help. It seems the files you attached are for a later edition of Comsol than I have (I have 5.2a). Is there anyway to work around this for my edition?
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Sorry, Jeremy, but in the Discussion Forum I can only offer to build model files in the current version of the software. Please consider upgrading to the current version.
-------------------Jeff Hiller
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Thats understandable. In any case, would it be possible to explain what kind of boundary conditions used in the model? This may enable me to get to the results I am looking for.
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Bottom, at x=0[mm], face: no x-direction displacement
Top, at x=1[mm], face: .01[mm] x-direction displacement
Vertex at (0,0,0): fixed constraint
Vertex at (0,0,1[mm]) : zero y-direction displacement
Jeff
-------------------Jeff Hiller