Chapter 4: Applying Loads and Constraints in an HBM Analysis

Consider the following distinctions and limitations when defining loads and constraints in an analysis:

  • Constraints applied using D commands must be real. Tabular constraints are not supported.

  • Loads must be defined either as a pressure (SF or SFE) or as a nodal force load (F). To apply different loads on the harmonics, a table (*DIM) with primary variable name Var1 = NHINDEX can be used as shown in the example below. 

    *dim,Ftab,TABLE,NH+1,1,,NHINDEX,FREQ
*vfill,Ftab(1,0),RAMP,0,1
Ftab(0,1) = Freq
Ftab(1,1) = F_H0    ! harmonic 0
Ftab(2,1) = F_H1    ! harmonic 1
F,2,FY,%Ftab%

  • If the load is not tabular and HBM cyclic is not activated (default CYCkey=0 on HBMOPT,CYCLIC), it is implicitly taken as a harmonic 1 load.

  • Loads other than pressure and nodal forces (temperature, etc.) are not supported.

  • Constraint equations (CE,CP) applied on the nonlinear element nodes are not supported.

  • For an HBM cyclic analysis (HBMOPT,CYCLIC with CYCkey=1) HBM Cyclic Analysis: Superelements Use Pass:

    • The DOF constraints (D commands) applied to the primary stage are internally copied to all higher time harmonics superelements (h > 0). All other DOF constraints are deleted.

    • The superelement load vector (SFE with Lab=SELV) created during a superelement generation pass can be used but an NHINDEX-based tabular load vector is not supported.

    • The loads can be defined using one of these two options:

      • At least one tabular load based on primary variable NHINDEX is applied on the primary stage using nodal forces (F) in the HBM analysis. With this option, the loads applied to higher harmonic superelements are deleted. The only loads considered are the loads applied to the primary stage.

      • No NHINDEX-based tabular load is defined. With this option, loads are directly applied to each single stage cyclic superelement.