Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Simple Tensile Test
Posted 16.11.2017, 13:16 GMT-5 Structural & Acoustics, Geometry, Materials Version 5.2a 5 Replies
Please login with a confirmed email address before reporting spam
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:
Please login with a confirmed email address before reporting spam
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:
Please login with a confirmed email address before reporting spam
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?
Please login with a confirmed email address before reporting spam
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
Please login with a confirmed email address before reporting spam
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.
Please login with a confirmed email address before reporting spam
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