Solving FEA problem of breast from supine to gravity-less configuration

[maverick269]

Hi,
I have a cae model of breast with skin, fat and a rigid back surface. These were created from solidworks using 3d surface images. Now my first step to get the unloaded configuration was to make sure the skin is in contact with the breast and breast with the back surface. So I am using surf-surf interaction properties to get the contact initiated reasonably (meaning it is not in perfect contact everywhere). Next I apply the necessary BCs and gravity load in appropriate direction to get unloading config. However, in this step, abaqus quits saying the time increment is too small. So my understanding is that I am either applying a completely off logic with regards to my gravity-less config here that abaqus can't solve this or the error is associated with the mesh type I am using or he BCs I am using here. Can anyone help me figure out what is wrong here. I am a beginner in abaqus and I would appreciate any help/suggestions I can get.
The cae file is here.

 

[corus]

It's not the cae file you've uploaded but a solidworks part.

 

[rstupplebeen]

This thread from a while back may be helpful.

http://www.eng-tips.com/viewthread.cfm?qid=306126

Rob Stupplebeen

http://www.optimaldevice.com

 

[maverick269]

Sorry, the cae file is here. One of them is 204 version and the other is 2012 abaqus version.

Thanks
N

 

[maverick269]

Forgot again, sorry novie to forums... here.

 

[rstupplebeen]

I don't see any gravity loads. You have provided displacements instead. You need to go to Loads-Gravity instead of BCs-Displacement/Rotation.

Right now you have defined contact between the 3 parts but there is nothing adhering them together. Likely you will experience rigid body motions. Simply fix the back of the fatty tissue and remove part v4-0-right-Back.

I understand that you want to model the skin sliding on the fatty tissue but the skin layer has a significant gap. You may be better off skinning the fatty layer with shells with appropriate thickness and material properties to the skin.

I hope this helps.

Rob Stupplebeen

http://www.optimaldevice.com

 

[maverick269]

Thanks Rob. I cannot remove the v4-0-right-back as I am thinking the whole breast will slide along the back surface depending on the load applied (like it does in actual breast geometry). So just fixing (encastre) the breast will not help visualize/achieve this effect. Here is the file with the right gravity load applied (in this cae I removed the skin to see if I can achieve this just for the main breast composed of fat). Any comments on why this step to remove gravity (effect) from natural breast position is not working?

Thanks
N

 

[maverick269]

I guess I had got the bodies too much in contact which was creating problems in the next steps. After I reduced to amount of contact, the step (unloading) ran fine.

Thanks
N

 

[rstupplebeen]

That's great that you are making progress. Good luck!

Rob Stupplebeen

http://www.optimaldevice.com

 

[maverick269]

Thanks Rob.