CMSOPT

CMSOPT, Cmsmeth, NMODE, FREQB, FREQE, Fbddef, FBDVAL, IOkey, --, --, Elcalc, --, Eigmeth, nStartVN
Specifies component mode synthesis (CMS) analysis options.

SOLUTION: Analysis Options

Product Restrictions

Cmsmeth

The component mode synthesis method to use. This value is required.

FIX	—	Fixed-interface method.
FREE	—	Free-interface method.
RFFB	—	Residual-flexible free-interface method.

NMODE

The number of normal modes extracted and used in the superelement generation. This value is required; the minimum is 1.

FREQB

Beginning, or lower end, of frequency range of interest. This value is optional.

The program always sets this value to zero if the residual-flexible free-interface method (Cmsmeth = RFFB) or the free-interface method (Cmsmeth = FREE) is specified via RESVEC.

FREQE

Ending, or upper end, of frequency range of interest. This value is optional.

Fbddef

In a free-interface (Cmsmeth = FREE) or residual-flexible free-interface (Cmsmeth = RFFB) CMS analysis, the method to use for defining free body modes:

FNUM	—	The number (`FDBVAL`) of rigid body modes in the calculation.
FTOL	—	Employ a specified tolerance (`FDBVAL`) to determine rigid body modes in the calculation.
FAUTO	—	Automatically determine rigid body modes in the calculation. This method is the default.
RIGID	—	If no rigid body modes exist, define your own via the RIGID command.

FBDVAL

In a free-interface CMS analysis (Cmsmeth = FREE), the number of rigid body modes if Fbddef = FNUM (where the value is an integer from 0 through 6), or the tolerance to employ if Fbddef = FTOL (where the value is a positive real number representing rad/sec). This value is required only when Fbddef = FNUM or Fbddef = FTOL; otherwise, any specified value is ignored.

IOkey

Output key to control writing of the complete transformation matrix on the .cms file to the .tcms file (FIX or FREE methods) or body properties to the .EXB file (FIX method).

CMS	—	Write the complete transformation matrix of the nodal component on the .cms file. For more information, see CMS File Format in the Programmer's Reference.
TCMS	—	Write the transformation matrix of the nodal component defined via OUTPR to a .tcms file. For more information, see TCMS File Format in the Programmer's Reference.
EXB	—	Write a body property input file (.EXB file) containing the condensed substructure matrices and other body properties for use with AVL EXCITE. For more information, see Ansys Interface to AVL EXCITE in the Substructuring Analysis Guide.

--, --

Unused fields.

Elcalc

Element calculation key:

NO	—	Do not calculate element results (default).
YES	—	Calculate element results and write them to the .cms file for the expansion pass.

--

Unused field.

Eigmeth

Mode extraction method to be used for the symmetric eigenvalue problem during the generation pass:

LANB	—	Block Lanczos algorithm (default).
SUBS	—	Subspace algorithm.
SNODE	—	Supernode algorithm.

nStartVN

Node number to be assigned to the first virtual node created to store the generalized coordinates. See "Notes" for more information.

Command Default

Issuing the CMSOPT command with no arguments is invalid. You must specify at least the CMS method (Cmsmeth) and the number of modes (NMODE). In a free-interface (Cmsmeth = FREE) or residual-flexible free-interface (Cmsmeth = RFFB) CMS analysis, the default method for determining rigid body modes is FAUTO (automatic).

Notes

CMS supports damping matrix reduction when a damping matrix exists. Set the matrix generation key to 3 (SEOPT,Sename,SEMATR) to generate and then reduce stiffness, mass, and damping matrices.

CMS does not support the SEOPT,,,,,RESOLVE command. Instead, the program sets the expansion method for the expansion pass (EXPMTH) to BACKSUB.

By default, the static constraint modes are not written to the .cms file for the fixed-interface and free-interface methods. Issue IOkey = CMS to write them.

If IOkey = TCMS, the transformation matrix is printed out and written to the .tcms file when the OUTPR command is issued with ITEM = NSOL and FREQ not equal to NONE. In addition, the transformation matrix is printed out when SEPR is equal to 1 or 2 on SEOPT. In interactive sessions, the transformation matrix is not output if the model has more than 10 elements.

For information about the component modes stored in the .cms or .tcms file, refer to Component Modes Storage.

If Elcalc = YES, the element results of the component modes included in the transformation matrix of the CMS method are calculated and written to the .cms file. This can significantly reduce the computation time of the The CMS Use and Expansion Passes in the Substructuring Analysis Guide. For limitations and available element results, see Calculating the Element Results in the Substructuring Analysis Guide.

Select a nStartVN value to offset the virtual node numbers from the other node numbers used in the model; otherwise, the program selects nStartVN to fulfill that condition. In the case of multiple superelements, if nStartVN is defined during each generation pass, then in the use pass, the virtual nodes of all imported superelements are gathered and renumbered from the nStartVN value specified for the first encountered superelement (first SE command). nStartVN can also be defined in the use pass via SE. (If nStartVN is defined by both the CMSOPT and SE commands, the larger number prevails.)

For more information, see Component Mode Synthesis in the Substructuring Analysis Guide.

This command is also valid in /PREP7.

Product Restrictions

Ansys Mechanical Enterprise PrepPost — Only CMSOPT,FIX,,,,,,EXB is supported.

Menu Paths

Main Menu>Preprocessor>Loads>Analysis Type>Analysis Options

Main Menu>Solution>Analysis Type>Analysis Options