### VERSION HISTORY LIRA-FEM

New types of perfectly rigid body (PRB)

# New types of perfectly rigid body (PRB)

Last updated: Jan 08, 2024 11:15:20

New types of PRBs are implemented.

Now, PRB may be one of the following types:

• All degrees of freedom (DOF)
• X, Y, Z, UX, UY, UZ
• Z, UX, UY
• Y, UX, UZ
• X, UY, UZ
• X, Y, UZ
• X, Z, UY
• Y, Z, UX
• X, Y, UX, UY, UZ
• X, Z, UX, UY, UZ
• Y, Z, UX, UY, UZ

Directions for the degrees of freedom(DOF) correspond to the directions of the local coordinate system of the master node.

The PRB was limited to type 1 ("All degrees of freedom") earlier. This meant that the slave and master nodes were connected by the identical values for warping (model type 6) and temperature (model type 15), in addition to the kinematic restraints between X, Y, Z, UX, UY, and UZ.

The 2nd type of PRB imposes only kinematic restraints between X, Y, Z, UX, UY, and UZ.

PRB of types 3-5 connect the displacements of the slave and master nodes as they move out of the certain planes. As a result, the displacements of the slave and master nodes are independent in this plane.

PRB of types 6-8 connect the displacements of the slave and master nodes in the certain plane. As a result, the displacements of the slave and master nodes are independent when they move out of the certain plane.

PRB of types 9-11 make the displacements of the slave and master nodes independent only along the appropriate axis.

Now, a node can serve as the master for multiple PRBs simultaneously.

Let’s consider modelling a slab-wall intersection, where the slab "leaves a trace" in the shape of a PRB in the wall and the wall "leaves a trace" in the shape of a PRB in the slab.

Example. How to use the PRB

Previously, the model in the figure was modelled by three PRBs:

1, 4, 5, 48, 51

2, 6, 7, 47, 50

3, 8, 9, 46, 49

Now this can be modelled with the six PRBs. This will release the degrees of freedom in the PRB in directions that do not require restraint. For example, so that the slab and wall nodes in the PRB can move freely from thermal heating.

1, 4, 5 (PRB type 3. Z, UX, UY)

1, 48, 51 (PRB type 5. X, UY, UZ)

2, 6, 7 (PRB type 3. Z, UX, UY)

2, 47, 50 (PRB type 5. X, UY, UZ)

3, 8, 9 (PRB type 3. Z, UX, UY)

3, 46, 49 (PRB type 5. X, UY, UZ)

That is, 1, 4, 5 is an unbending body in the XOY-plane, but can deform in that plane,

and 1, 48, 51 is an unbending body in the YOZ plane, but can deform in that plane.

Important.

When you open the problems generated in previous versions, all PRBs are of type 1 (all degrees of freedom).

A slave node can be part of only one PRB and a slave node cannot be a master node.