Coupling displacements

Coupling displacement coordinates (VECTOR)

The CLIENT=VECTOR coupling restriction can be used to fully couple a bunch of nodes. The client nodes inherit both, the direction and the length of the master node.

The following two parameters are entered for coupling displacement coordinates:

        
          CLIENT = VECTOR
          CS = name_of_coord_system
        
      

The procedure involves calculating the difference between the current coordinates and start coordinates of the master node in relation to the coordinate systems referenced by CS. Then the start coordinates of the client nodes are calculated in relation to the coordinate system, the difference of the master node is applied and the current coordinates of the client nodes are determined (see the following figure).

It is also possible to couple only single displacement coordinates by adding options to the standard form of the CLIENT=VECTOR parameter:

        
          CLIENT = VECTOR, ON/OFF, ON/OFF, ON/OFF
          CS = name_of_coord_system
        
      

Each of the three coordinates can be set to either ON or OFF. Only those displacement coordinates set to ON are coupled. Displacement coordinates set to OFF are not taken into consideration for the coupling. The default setting is VECTOR=ON, ON, ON.

Important: The coordinate system referenced by CS can be a Cartesian coordinate system or a cylindrical or spherical coordinate system. If the coordinate system is Cartesian, all nodes have the same displacement vector (given the name CLIENT=VECTOR), i.e., all nodes are moved translational like a 'rigid body'. All nodes have the same displacement direction and the same amount of displacement. If the coordinate system is cylindrical or spherical, the displacement vectors of the master node and client nodes with respect to the global Cartesian coordinate system can generally differ. Corresponding coordinates are determined in the relevant coordinate system. For example, if a group of moving nodes allocated in a circle have the same radial coordinates in relation to a cylindrical coordinate system and are coupled with respect to this coordinate system, the nodes of the final design will always lie on the same circle.

Coupling displacement direction (DIRECTION)

In contrast to the above CLEINT=VECTOR coupling restriction, this one can be used to couple only the directions. But every node can stay with individual lengths.

The following two parameters are entered for coupling the displacement direction:

        
          CLIENT = DIRECTION
          CS = name_of_coord_system
        
      

The procedure is the same as that for CLIENT=VECTOR, but with the difference that the retained displacement vector is rescaled to the original displacement amount of the client nodes (see the following figure).

Important: The coordinate system referenced by CS can be a Cartesian coordinate system or a cylindrical or spherical coordinate system. If the coordinate system is Cartesian, all nodes have the same displacement vector (given the name CLIENT=VECTOR), i.e., all nodes are moved translational like a 'rigid body'. All nodes have the same displacement direction and the same amount of displacement. If the coordinate system is cylindrical or spherical, the displacement vectors of the master node and client nodes with respect to the global Cartesian coordinate system can generally differ. Corresponding coordinates are determined in the relevant coordinate system. For example, if a group of moving nodes allocated in a circle have the same radial coordinates in relation to a cylindrical coordinate system and are coupled with respect to this coordinate system, the nodes of the final design will always lie on the same circle.

Coupling amount of displacement (LENGTH)

In contrast to the above CLEINT=VECTOR coupling restriction, this one can be used to couple only the optimization length. But every node can stay with individual directions.

The following parameter is entered for coupling the amount of displacement:

        CLIENT = length
      

The procedure is as follows: The amount of displacement of the master node is calculated and the displacement direction of the master node is determined (growth or shrinkage). The displacements of the client nodes are scaled in such a way that the displacement amount of the master node is retained (see the following figure).

Coupling coordinates in the FE displacement coordinate system (DISP_CS)

The nodes are fully coupled like with the CLIENT=VECTOR restriction, but the nodes are moved in their local coordinate system.

The following parameter is entered for coupling the coordinates in the FE displacement coordinate system:

        CLIENT = DISP_CS
      

The procedure is as follows: The optimization displacements (coordinates) of the master node with reference to the FE displacement coordinate system are transferred directly into the FE displacement coordinate system of the client nodes. It is also possible to couple only single displacement coordinates by adding parameters to the standard form of the CLIENT=DISP_CS parameter

        CLIENT = DISP_CS, ON/OFF, ON/OFF, ON/OFF
      

Each of the three coordinates can be set to either ON or OFF. Only those displacement coordinates set to ON are coupled. Displacement coordinates set to OFF are not taken into consideration for the coupling. The default setting is DISP_CS=ON, ON, ON.

Important: The FE displacement coordinate system of the coupled nodes must be of the same type, i.e. either Cartesian, cylindrical or spherical. Each node can have its own FE displacement coordinate system. Alternatively, if all nodes have the same FE displacement coordinate system, an identical link condition with CLIENT=VECTOR can be defined.