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
>