A model for an HBM analysis is generally partitioned into a linear part and a nonlinear part, as shown in the following figure. Only specific nonlinearities can be included in an HBM analysis. These are described in detail in the next section, Nonlinear Elements Supported in an HBM Analysis. There are no specific guidelines for modeling the linear part of an HBM analysis. For more details, see Linear Part of the Model.
For modeling limitations, see Limitations.
If your model is cyclically symmetric and if the nonlinearity is located within a sector, the multistage cyclic symmetry procedure can be used to reduce both the size of the problem and the solve time. Depending on the problem, you can choose either one of the following procedures:
For engine order 0 excitation, the single stage (MSOPT) cyclic procedure with harmonic index 0 can be used directly. In that case, the HBM cyclic option should not be activated, the duplicate sector is not present, and the stage should not be a superelement. For an example problem demonstrating this, see VM319: Nonlinear Harmonic Analysis of a Cyclic Chain of Oscillators.
For all other cases (including engine order 0 excitation with single stage superelement), the HBM cyclic option must be activated (HBMOPT,CYCLIC with
CYCkey=1). The spatial harmonics are represented by single stage cyclic superelements. Each time harmonic corresponds to a spatial harmonic. The details are presented in HBM Cyclic Procedure. For examples demonstrating this procedure, see Example 4: Cyclic Spring-Mass System with Cubic Nonlinearity and Example 5: Cyclic Model with Solid Elements and Frictional Contact.