question to apply a new boundary condition each time step

[Liam]

Dear Professors and mates,

As I mentioned at the title, I met a case that I need re-apply the boundary condition every time step. But not for the mechanical properties. Some other degrees of freedom will be redescribed at each time. Therefore, I am asking if it is possible to have this advantages and how can I approach this simulation in FEAP?

Many many thanks for your kind help and I am looking forwards to your patient reply.

Best regards,

Liam

[FEAP_Admin]

Is it the boundary values that are changing or is the character of the boundary conditions (force versus displacement) that are changing?

[Prof. R.L. Taylor]

Liam,

Can you be more specific on how the boundary inputs are determined.  Does the solution to the problem define what you need to chang or are you determining it by another known approach? Feap allows you to go into "mesh" each step, however it would be tedious to have a data set for each step.  It seems you need to have a user macro that can do it for you.  But we need more information to guide you for that.

[Liam]

Dear Prof. Taylor and FEAP_ADMIN,

Actually I want to solve a problem that after each time step, the boundary condition for some other DOF like (temperature or moisture whatever) will be updated, and I want to find the mean value of whole structure and apply this mean value to every nodes again for the next time step as a new boundary condition. Therefore, theoretically, I need to define the boundary condition each time step. But I am wondering how can I achieve this by using macro routines?

Another question for the pointer np(*), which one represent the material sets? Since if I just need part of the elements do this reapplying boundary, I need to make a check to do this.


Many many thanks for your kind and patient help.

Best regards,

Liam

[Prof. R.L. Taylor]

The material number for each element is at ix(nen1,*)

So you need a user macro to loop over elements and for the materials that affect bc compute value.

You could use an isw and formfe.f todo contribution to avg in your element. Say isw=55.

[Liam]

Dear Prof. Taylor,

Many many thanks for your help and I will try this out. If I meet further problems, probably I will bother your again.

Best regards,

Liam