Female breast under zero-gravity 2

[mual]

Hi every one,

I am doing a Biomechanics research of female breast cancer, i am using ANSYS 12 to solve my FEM problems.

I have the mesh of deformed breast under itself weight (from a 3D RMI images) and i would like to know if it is possible to get the zero-gravity mesh of that breast. So i can apply the gravity in another direction.

 

[mual]

Hi again, we know the deformed shape of breast under gravity, so we need to solve a backward problem to have a reference state. Could ansys do that? Help needed!

Thanks and best regards

 

[Stringmaker]

I think it can. If you know the deformed shape w/ 1g of load couldn't you apply a -1g inertial load and solve for the undeformed shape in this manner?

The most correct way would be to apply stresses as initial conditions to the deformed configuration of the breast and let the problem find the undeformed configuration. I seems that it'd be difficult to know what stresses are present in the tissue to apply as initial conditions though.

-Brian

 

[mual]

Hi brian, thank you for reply, actually i tried to apply -g internal load, maybe it is good for approximation but didn’t give the exact result due to shape deformation and displacement of the center of mass of the studied geometry and for each elements.

Actually i don’t know how to apply stresses as a initial conditions because i just have the final deformed shape and the internal force, can you please give me some hints to do it?
thank you again

 

[Stringmaker]

Initial stresses are applied with the INISTATE command. That's the easy part...knowing what those stresses and/or strains are is the difficult part.

 

[flash3780]

I'm just curious... do you have material property data for... erm... boob?

 

[mual]

Hi brain, my question was about the difficult part.

Hi flash, yes i know the material propert actually breast has three tissues and all of them are hyperelastic (rubber-like) material.

 

[flash3780]

Perhaps the undeformed shape could be approximated with by a "guess-and-check" methodology on a 2D model. You could build a parametric model of an undeformed breast, apply a gravity load and adjust the initial shape based on the results. As long as the model runs quickly, you could probably hone in on a shape in a reasonable amount of time.
You could probably automate this process, but seeing as there are likely quite a few parameters defining the shape of the breast, it might be easier to adjust them manually.

 

[mual]

Hi again flash, thank you for your reply, it is a good idea, but i have a huge 3D mesh with 3 milliones of nodes and it is imposible to be adjusted manually.
I have another question, i start to use ansys 13, in this version there is no real constant for shell 181 or shell 281 and I dont know how to define the thickness of shells!!

best regards and merry christmas