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 cores regardless of the number of cores specified.

Shared-memory parallel (SMP) is not supported.

The HBM solution cannot be restarted (ANTYPE,,RESTART).

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 is limited to a single harmonic index, HI = 0 stage without a duplicate sector. For HI > 0, to take into account the coupling between time and spatial harmonics, HBM cyclic must be activated (HBMOPT,CYCLIC with CYCkey=1) and single stage cyclic superelements must be used.

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.