*MPC

Keyword type: model definition

With this keyword card a multiple point constraint is defined, usually a nonlinear one. Right now, four different MPC's can be selected.

• A plane MPC (name PLANE). This MPC specifies that all nodes listed within this MPC card should stay in a plane. The first three nodes are the defining nodes and should not lie on a line. For all subsequent nodes a nonlinear MPC is generated expressing that they stay within the plane. Notice that the plane can move during deformation, depending on the motion of the defining nodes.

• A straight line MPC (name STRAIGHT). This MPC expresses that all nodes listed within this MPC card should stay on a straight line. The first two nodes are the defining nodes and should not coincide. For all subsequent nodes two nonlinear MPC's are generated expressing that they stay on the straight line. Notice that the straight line can move during deformation, depending on the motion of its defining nodes.

• A beam MPC (name BEAM). This MPC involves exactly two nodes the distance between which is kept constant during the calculation.

• A user MPC (name to be defined by the user). With this option the user can define new nonlinear MPC's. Examples are given in Section 8.7, e.g. the mean rotation MPC.

Since the 3-D expansion of standard beam, shell, plane stress, plane strain and axisymmetric elements frequently involves the use of extra linear equations and/or nonlinear MPC's such as knots, the additional application of nonlinear MPC's to such elements is problematic. Therefore, it is not allowed to apply STRAIGHT, PLANE, BEAM and MEANROT MPC's to any node belonging to such elements.

A *MPC card automatically triggers the NLGEOM parameter, i.e. a geometrically nonlinear calculation is performed, except if the MPC is a mean rotation MPC.

There are no parameters for this keyword card.

First line:

• *MPC

Second line:

• MPC name
• list of nodes participating in the MPC: maximum 15 entries. Zero entries are discarded.

Following lines (as many as needed):

• list of nodes participating in the MPC: maximum 16 entries. Zero entries are discarded.

Example:

*MPC
PLANE,3,8,15,39,14

specifies that nodes 3, 8, 15, 39 and 14 should stay in a plane. The plane is defined by nodes 3, 8 and 15. They should not be co-linear.

Example files: beammr, beamplane, beamstraight.