karthickraja liked a post in a topic by Simon Križnik in *DOUBT* RBE2 & RBE3
RBE2 and RBE3 are rigid links in FEM used for load transfer. These elements in fact will not deform as they are considered to be infinitely rigid (diamond under atmospheric pressure for example even though it's not infinitely rigid) and the sole purpose of these elements is to transfer the loads between the grid points or nodes. RBE2 transfers the loads in such a way that all the slave (dependent) nodes have zero relative deformation after the load application. Whereas RBE3 transfers the load using weighted average of slave nodes(independent nodes) position.
Perhaps you will understand even better:
karthickraja liked a post in a topic by monu in Need some help in project
I am Sanjeev Kumar, currently pursuing my Mechanical Engineering from Pune University, India. Sir, we are working on a project based on Biomimetics of a butterfly. In this project, we have to analyze the motion of the butterfly while in motion. We have to perform CFD and crash analysis of the butterfly in Altair/LS Dyna as the one shown in the attached GIF.But we don't know this is possible in HyperWorks or not if not can we take help of Ls Dyna.because the major problem we are facing is how to apply motion to the wings of a butterfly and how to apply moving mesh to simulate this. If it is possible then please help me that how can we do this we are unable to find tutorials on the internet. Sir it would be great if you will help. Thanking you in anticipation With warm regards sanjeev kumar firstname.lastname@example.org 7030305737
karthickraja liked a post in a topic by tinh in Why 3D elements have only 3 Degrees of freedom?
I had exactly same questions when i was in university and no teacher told me answer, unfortunately my fe textboooks just say that brick has 3 dofs/node, shell 6dofs/node,... but do not explain
then i have to imagine (actually similar to when i was processing of mechanical parts):
- when I lathe a shaft (ROD), i have to position one end fully in a clamper (like a tube), so ROD need 6 dofs/node to be fully constrained
- when I punch a sheet (SHELL), i have to position one corner with 5 dofs and one other corner 1 dof (in-plane rotation), so SHELL has 5 dofs/node, remain in-plane rotation dof is constrained by adjacent node, so you never let 2 shell elements connect together by only 1 node (cannot transfer moment). But some solvers may provide particular SHELL has fully 6dofs/node, like CQUADR in nastran/optistruct
- when I mill a block (BRICK), i have to position 3 faces so it cannot move in 3 directions, after position 3 faces then it cannot rotation around 3 axles also because each plane (face) constrained rotation dofs. so BRICK have 3 translation-dofs/node and it is enough to transfer moment
put more dofs in to a fully position part (element) will make it over-constrained (too stiff)
and be careful when connect 1d to 2d, 2d to 3d or 1d to 3d, you have to take into account all dofs have to be constrained