The nodes of nonlinear elements must be attached to linear elements. Chained nonlinear elements without connected linear elements (with unconstrained shared nodes and DOFs connected to nonlinear elements only) are not supported.

NROPT,UNSYM is ignored for HBM nonlinear elements. Unsymmetric matrices are used for CONTA178 only if the coefficient of friction specified for the element material is greater than or equal to 0.2.

Distributed-memory parallel (DMP) processing uses two MPI processes regardless of the number of processes specified.

Shared-memory parallel (SMP) is only available for the nonlinear multiharmonic MPI process (HBM Analysis and Parallel Processing).

Damping applied to non-linear elements: Rayleigh damping applied to the nonlinear elements is ignored (BETAD, ALPHAD, MP with Lab = BETD/ALPD).

Damping applied to linear elements: Damping is supported in linear elements except for structural damping (DMPSTR, MP with DMPS, and TB,SDAMP with TBOPT = STRU). Also, frequency-dependent damping is not supported.

HBM analysis of a prestressed structure through the linear perturbation procedure is not supported. To add prestress in the linear elements, a prestressed superelement can be used instead (see Model with Prestressed Superelement).

The expansion pass of superelements is not supported for any result type.

The cyclic symmetry procedure (initiated with CYCLIC), with or without superelements, is not supported.

The multistage cyclic procedure (see the Multistage Cyclic Symmetry Analysis Guide) can be used to reduce the size of cyclically symmetric structures. The procedure can be directly used for a single harmonic index, HI = 0 stage without a duplicate sector. For HI > 0, you must account for the coupling between time and spatial harmonics by using the HBM cyclic procedure (HBMOPT,CYCLIC with CYCkey=1) and single stage cyclic superelements. For more details, see HBM Cyclic Procedure.

During the restart procedure, the following must remain unchanged:

When using the multistage cyclic symmetry procedure, nonlinear elements must be located inside the model sector. Nodes attached to nonlinear elements located on the cyclic sector edges are not supported.

If CONTA178 is used, note that it cannot be attached to quadratic elements. See Creating Geometry and Meshing the Model in the Contact Technology Guide.