Currently I'm working on aortic wall prestrain for which theoretical solution exists, nevertheless I'm having trouble using the FEBio prestrain plugin to use a prestrain field as initial condition.

First, the forward problem I'm solving is simple inflation by prescribing uniform pressure in the lumen. The boundary conditions are: no displacements in z (axial direction) for all nodes on the top and bottom surface, this is to impose a 2D solution. I'm fixing the lowest node (lower y coordinate) in the lumen. And finally I'm preventing movements in x directions to the lowest node (lower y coordinate) in the outer adventia to prevent rotation (no rotation node).

We are trying to impose a prestrained initial condition to this forward problem. We found that imposing the same boundary conditions for the prestrain step leads to divergence in that step unless a really small prestrain field is imposed.

Then, we tried different boundary conditions. We finally achieved convergence on the prestrain step if we completely fix one of the flat surfaces (either top or bottom) and kept the restrictions of the fixed node and no rotation node. Nevertheless, despite the prestrain step converges, the following steps (the forward problem) fail to converge. We tried reducing the time steps to 0.0001 and changing the quasi-Newton update method with no results.

We really appreciate any advice or hint on how to address this problem. I don't find a way to attach my .feb files in this new forum format.

Thanks and regards,

Johane Bracamonte