uniaxial compression test

[Xanatos82]

Hi all, I'm tryin to model with FeBIO (a FEM open source software) an uniaxial (force driven) compression test, on a specimen of muscle (modeled as a Mooney Rivlin material).
My specimen is a cube of 100 mm x 100 mm x 100 mm, laid on a plate (rigid body) and with the load applied by an upper plate (rigid body too).
I've problem with instability (i added contact conditions between the bottom face of the cube and the bottom plate, and with the top face of the cube and the upper plate) and a BC of 0 displacement in Z direction for the bottom plate of the cube, but it's not enough because the cube could translate and go away during the analysis, but if I lock the X and Y of the faces, obviously the cube couldn't expand under compression.
So, because the way to do, is not different from Abaqus, what other BC i've to apply to have a realistic solution?

 

[rb1957]

ensure your constraints react the 6 rigid body freedoms. your z constraint reacts 3. you need two x (parallel, not in a line) and 1 y (or two y and 1 x) to react the other three. these should not restrict the deflection of the model.

Quando Omni Flunkus Moritati

 

[rstupplebeen]

I would use the 3 symmetry planes and only model 1/8 of the sample and only 1/4 of 1 compression platen. With the symmetry constraints your rigid body motions should be constrained. I hope this helps.

Rob Stupplebeen

http://www.optimaldevice.com

 

[GregLocock]

Lock the middle node of the bottom face of the cube to the platten, or add some soft springs laterally to stop it running away.
I've got to say I think you are exploring friction more than the elasticity and poissons ratio of the material.

Cheers

Greg Locock


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