Be aware of the following considerations when setting up your cyclic symmetry analysis:
Consider the following distinctions and limitations when defining a cyclic symmetry model:
Cyclic symmetry solution does not work for elements that have thermal and hydrostatic pressure degrees of freedom.
Note: Cyclic symmetry modeling of static and transient thermal analyses are supported in the Mechanical Application using the Cyclic Region object (See Cyclic Region Overview in the Mechanical User's Guide).
The following structural element types are not supported:
Axisymmetric elements (such as PLANE83)
Generalized axisymmetric elements (such as SOLID272)
Thermal surface effect elements (such as SURF151)
Reinforced elements (such as REINF263)
User-defined element (USER300)
Superelement (MATRIX50)
Generalized plane strain option (such as PLANE183 with KEYOPT(3) = 5)
Birth and death of elements (EKILL and EALIVE) is not supported in a cyclic symmetry solution.
A cyclic model generated while having solid model based cyclic edge components does not write cyclic data to the .cdb file if CDWRITE is issued with
Option= DB. A warning is issued that you must reissue the CYCLIC command after a CDREAD of the model. You must also reissue any CYCOPT and CYCFREQ commands previously issued, as they are not written during the CDWRITE operation in this case.Initial state (INISTATE) is not supported for layered elements. Only stress and strain initial states are supported for non-layered elements
Constraint and joint elements (MPC184) are permitted with cyclic symmetry. However, these elements cannot attach to a cyclic high or low edge, including the cyclic axis, nor can they attach to a surface attached to the cyclic high or low edge. Also, non-cyclically symmetric loading is not supported with constraint/joint elements. Constraint and joint elements are not supported for full linear perturbation harmonic cyclic symmetry analyses.
Consider the following distinctions and limitations when defining loads for a cyclic symmetry model:
General non-cyclically symmetric loading (CYCOPT,LDSECT) is only supported for static and full harmonic solutions. General non-cyclically symmetric loading is not supported for cyclic mode-superposition harmonic analyses.
When cyclically-symmetric loading is applied, non-cyclically symmetric loading defined using the CYCOPT,LDSECT command is ignored. If a combination of cyclically symmetric and non-cyclically symmetric loading is desired, both types must be applied using the CYCOPT,LDSECT command.
Engine-order loading (or traveling wave excitation) (CYCFREQ,EO) is only supported for cyclic mode-superposition analyses.
For modal restart used to generate loads for cyclic mode-superposition, loads cannot be applied on nodes on the cyclic boundaries or on elements that lie on or adjacent to the cyclic boundary. Note that body loads (e.g. OMEGA, ACEL) that are typically applied to an entire body or component also cannot be applied on the cyclic boundaries.
Note the following regarding the use of pilot nodes (or remote points):
Pilot nodes may be used to apply force-distributed constraints (KEYOPT(4) = 1) and rigid constraints (KEYOPT(4) = 2) for both forces and displacements using multipoint constraints (KEYOPT(2) = 2) or the Lagrange multiplier method (KEYOPT(2) = 3). See Multipoint Constraints and Assemblies and the table of contact element key options in Defining Surface-Based Constraints in the Contact Technology Guide.
Loads and displacements applied through a pilot node placed on the cyclic axis are multiplied by the number of sectors, Nsect, as they are applied to all sectors of the model. For example, consider a single load applied to the sector, which is directed along the z-axis (aligned with axis of symmetry), Fz. The total load applied to the structure will be Fz * Nsect (not Fz).
Only Fz (F,,FZ), Mz (M,,UZ), Dz (D,,UZ),Drotz (D,,ROTZ), and fixed constraints (D,,ALL) are supported.
Only static analyses (ANTYPE,STATIC) are supported.
The target elements on the surface where the boundary conditions are applied must have KEYOPT(6) = 2. For details, see Additional Guidelines for a Force-Distributed Constraint and Additional Guidelines for a Rigid Surface Constraint in the Contact Technology Guide.
The pilot node should be created after a call to the CYCLIC command.
The pilot node must be rotated (NROTAT) into the cyclic coordinate system.
A single pilot node that is not on the cyclic axis and is attached to a sector will behave like one pilot node per sector in the expanded solution.
If a nodal load is applied on both low and high edge nodes, it will be taken into account twice in the solution due to the cyclic constraint equations.