[CIG-SHORT] Initial stress interaction with Dirichlet bc

[Brad Aagaard]

Ekaterina,

It sounds like you are trying to do the following:

t=0: Apply Dirichlet BC that constrain the normal displacements on the 
+x, -x, +y, and -y boundaries.

t>0: Apply Dirichlet BS on -y boundary constraining the x and y 
displacements; apply Dirichlet BC on +y that constrains the y 
displacement (constant rate as a function of time).

PyLith does not currently support changing which DOF are constrained as 
a function of time.

You can either (a) use a static simulation or initial stresses to create 
the stress distribution at t=0 (assuming you have a linear elastic 
material) or (b) use Neumann BC in combination with Dirichlet BC.

For (b) I think you would do something like:

i. Neumann BC with normal tractions on -x, +x, and +y.

ii. Dirichlet BC on -y as in t>0 with x displacement compatible with the 
compression in the x direction associated with the Neumann BC. Dirichlet 
BC on x component of +y as in t>0 compatible with the  compression in 
the x direction associated with the compression.

If you have a homogeneous linear isotropic material, then I would just 
impose the initial stresses associated with the compression. Otherwise, 
I think you will need to use a static simulation and take the output and 
apply them as initial stresses.

Regards,
Brad


On 01/20/2017 11:43 AM, Ekaterina Yevgenyevna Bolotskaya wrote:
> Dear Developers,
>
> I'm currently working on a 2D simulation where I need to initially
> compress a 2D block in both directions and then fix both displacements
> of lower horizontal boundary and apply a horizontal displacement rate on
> the upper horizontal boundary.
> The problem is that my initial compression interacts with my Dirichlet
> bc: I have the whole block compressed but the horizontal boundaries
> themselves (I'm talking about time 0, when there's no rate yet). I get
> smth like this:
>
>
> While I want to compress the whole block uniformly and only after have
> the compressed block fixed.
> Could you tell me if I can do that and how?
>
> Thanks!
>
>
>
> Best regards,
> Ekaterina Bolotskaya
>
> PhD in Geophysics,
> Earth, Atmospheric and Planetary Science Department,
> Massachusetts Institute of Technology
> E-mail. bolee at mit.edu
> Mob. +1 (857) 284-2805 <tel:%2B1%20%28857%29%20284-2805>
>          +7 (963) 995-36-33 <tel:%2B7%20%28963%29%20995-36-33>
>
>
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