Learning Forum

[Jurjen]

Dear readers,

For a project I am trying to simulate palpation using a pressure field (Acoustic radiation force/ARF) and the formation of shear waves thereafter.

Since I know the pressure field from the ultrasound probe I import this in a plane as pressure boundary condition. This step works fine and gives me the palpation effects of tissue as expected. (see also picture below).

But after the first step I am aiming at removing this pressure BC to see the bounce back of the indentation/palpation caused by the ARF. First I tried to deactivate my imported pressure at the end time of step 1 to have no pressure left in step 2. But this didn't work and the palpation would just continue as it did in step 1 (unitl it crashes).

Thereafter I tried the same but by adding an APDL command which should remove the imported pressure at the beginning of step 2 (SFEDELE command, as i saw pressure was imported via SFE command). But this also resulted in continued palpation. (I also checked this step by listing the SFE loads, which said there were none left).

At first i thought this could be some momentum left in the tissue which caused the tissue to further indent before bouncing back. But after looking more closely to the results I saw the deformation had a steady rate and was not slowing down or bouncing back.
Therefore I think there are some reaction forces or other forces in my simulation still there after removing the pressure loads. But I actually don't know where they are.

Therefore I was hoping someone could give me an indication where my simulation goes wrong. I added my Workbench project in the attachements. 

Thanks in advance

 

Jurjen

[Jurjen]

I am sorry, hereby the attachement: https://drive.google.com/open?id=1KrGKY-Wc_RF5avPLoCacqbM7iKmQUHlc