Good day!
I've been trying to figure out how to create my own element and studies
ChElementBeamEuler
to understand how to construct it correctly.
First, I was trying to determine all the coordinates systems for components
of the equations (in particularly for ShapeFunction) and meet the following
code
void ChElementBeamEuler_63::GetStateBlock(chrono::ChVectorDynamic<> &mD) {
mD.resize(9);
ChVector<> delta_rot_dir; double delta_rot_angle;
// Node 0, displacement (in local element frame, corotated back)
// d = [Atw]' Xt - [A0w]'X0
ChVector<> displ = this->q_element_abs_rot.RotateBack(nodeA->Frame().GetPos
())
- this->q_element_ref_rot.RotateBack(nodeA
->GetX0().GetPos());
mD.segment(0, 3) = displ.eigen();
...
If I understand everything correctly
[Atw]' Xt - is current position of nodeA rotated into the current element
orientation
[A0w]'X0 - is the original position of nodeA rotated into the original
element position
Since
Xt = nodeA->Frame().GetPos()
X0 = nodeA->GetX0().GetPos()
Xt and X0 are both in the same (world) frame (coordinate system)
But again the [Atw] != [A0w] and we get that vector [Atw]' Xt and [A0w]'X0
are in different coordinate systems!!!!
How comes?!!
Maybe I miss something... If anyone knows what's going on, please explain=)
On Tuesday, January 16, 2024 at 12:47:51 PM UTC+3 Vic M wrote:
> Hello, everyone
>
> I've been trying to solve my problem with modal reduction for some time
> now with no significant success. Despite my model has finally been reduced
> (the correct way to do it I'll describe later in the my conversation) the
> DoFs are still to many. The reason is the abundance of boundary nodes and
> links between them and the interface node.
> The only way to solve this (as I see it, may be I'm wrong) is to attach
> these nodes not with links but with finite elements. The problem is that I
> need to attach ChNodeFEAxyz to ChNodeFEAxyzrot and there's no such an
> element (I couldn't find one at least).
>
>
> So finally my question: Is there any guide how to create an element? I
> guess the ChElementGeneric class should be somehow inherited and
> reimplemented with the new element math?
> Thanks in advance
>
> ________________________
> Best regards,
> Victor
>
>
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