Topic: Traction Boundary condition for structural 2D and 3D elements

I am trying to apply traction BC's on an element. The constant edge load and constant surface load functions are not really adequate to apply general traction bc's. Let me be more clear. For example lets say i want to do apply a constant shear on a curved surface, then the only options present are to prescribe the x and y components of this on the element side, however, this would mean calculating the x and y comonents on each element with an assumed normal and then computing the values before hand and applying. Now for large deformation problem, if the normal vector changes, then there is no easy way to give assume that the x and y components will be the same as the material deforms.

My interest is the following. I have a problem where i would like to specify the actual traction and hopefully oofem can handle the change of the normal direction.

Cheers

Re: Traction Boundary condition for structural 2D and 3D elements

If I understood correctly, you want some kind of follower load. For that, you need a new boundary condition, which can be inherited from ActiveBoundaryCondition class, that assembles contribution to the rhs vector during each iteration and you can also implement contribution of your bc to the stiffness matrix.
Than I guess you would also need some interface from which all elements that support this boundary condition need to be inherited and implement the required functions.

Let me know, I can help you to implement it.

Re: Traction Boundary condition for structural 2D and 3D elements

Thanks for the response. Actually that is not what i am looking for.

What i am looking for is to compute the traction's on an element side with arbitrary stress state.

Assuming that i can provide the stress state at any element side integration point, is there a way to compute the equivalent nodal forces. I am looking to see what routines are available in oofem that will allow me to do this.

Cheers

Re: Traction Boundary condition for structural 2D and 3D elements

The nuemann type bcs for computational homogenization is _slightly_ similar to this.

There is also the option of specifying bcs in element local cs, which is the closest youll find in oofem presently.