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2.5  ABAQUS interfacing

• Non-linear springs
• Superelement generation (Craig-Bampton type)

For generalities about superelements see section 1.6.1. This section discusses the specifics of superelement generation using ABAQUS.

2.5.1  Non-linear springs

For spring representations of volumes or surfaces, a first common approach is to use so called rigid elements.

Abaqus supports several types

• *KINEMATIC COUPLING : rigid connections where the spring is connected to a master node with 6 DOF which enforce motion of a number of slave DOFs.
• *DISTRIBUTING COUPLING (RBE3) : flexible connection where the spring is is connected to a slave node with 3 or DOF which depend from a set of master nodes.
• *COUPLING : specific surface based definition, followed by either a *KINEMATIC card for rigid or *DISTRIBUTING card for RBE3 formulations.
• *MPC : node based definition with type BEAM to constraint 6 DOF per node or type PIN to constraint the 3 translations only.
• *CONNECTOR : connectors provide advanced structural kinematics, type BEAM without elasticity definition provides a rigid connection (linearized in SDT).
• *EQUATION : generalized MPC definition with a direct constraint matrix declaration.

2.5.2  Superelement generation (Craig-Bampton type)

Superelement generation in Abaqus is divided in three steps.

• *STEP, PERTURBATION//*STATIC used to define residual vectors. Note that export of residual loads associated with non-linearities is not yet implemented in SDT.
• *FREQUENCY, EIGEN=LANC to compute internal modes with possibly a Craig-Bampton interface declared by a *BOUNDARY card.
• *SUBSTRUCTURE GENERATE to generate and export the superelement, use *RETAINED NODAL DOF associated to fixed DOF in the frequency step for a Craig Bampton reduction.

 See SeGenResidual.inp