OK, good luck with that!
r.
On 03/18/2016 11:32 AM, Ronghai Wu wrote:
Hi Robert,
I thought it over, and I noticed what I wanted to do just could not help that much in scientific point of view but complicate solving procedure. So, I will use periodic displacement boundary condition. Anyway, thanks always for your help.
Regards Ronghai
在 2016年3月18日星期五 UTC+1上午11:16:37，Robert Cimrman写道：
Hi Ronghai,
So you mean something like enforcing a symmetric deformation of the neck? That should be automatic, provided the mesh is good enough and the loads/BCs are symmetric.
As for constraining the strain, maybe you would need some kind of a mixed formulation, where strain is an independent variable, but I am not sure I understand what you want to achieve.
r.
On 03/16/2016 12:00 PM, Ronghai Wu wrote:
Hi Robert,
Thanks for your reply. Here I do not mean periodic displacement boundary condition, but periodic strain boundary condition. The reason is, still taking 2D uniaxial tension along y direction as example. If I fix the "u.x" both at top and bottom boundary. There will be necking at left and right boundary as tension goes on (but I do not want to have free surface boundary condition). However, if using periodic displacement boundary condition, there would be no displacement at left and right boundary, and the elastic stress-strain would be larger than free surface case. I am thinking if there is periodic strain boundary condition, then the necking is retained and stress-strain would be between free surface and periodic displacement cases. So, I am wondering is it possible to have periodic strain boundary condition in sfepy, sounds kind of odd though.
Regards Ronghai
在 2016年3月15日星期二 UTC+1下午10:28:54，Robert Cimrman写道：
Hi Ronghai,
you can constrain the displacements using the periodic boundary
conditions
- then the strain on the boundaries would be the same as well. Or you need something else?
r.
On 03/15/2016 03:26 PM, Ronghai Wu wrote:
Hi sfepy developers and users,
I am wondering is it possible to have periodic strain boundary condition in sfepy? For example, in a 2D uniaxial tension along y direction, how to constrain the strain at left and right boundary to be same when solving mechanical equilibrium equation?
Regards Ronghai