CMSMETH (Bulk Data Entry)

Bulk Data Entry

CMSMETH – Component Mode Synthesis Method Definition

Description

CMSMETH defines the CMS (Component Mode Synthesis) method, frequency upper limit, number of modes, and starting SPOINT ID to be used in a CMS solution. The eigenvalue solver is also specified. In addition, preload as well as loads for reduction and residual vector generation can be defined. Also, an ASCII file containing CELAS4 and CDAMP3 element data and/or their corresponding design variable definitions can be generated for DMIG to allow the use of the component modes in optimization runs.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
CMSMETH	CMSID	METHOD	UB_FREQ	NMODES	SPID	SOLVER	AMPFFACT	SHFSCL

Optional continuation lines for Fluid Analysis
(mandatory if a minimum of 1 Fluid grid is present in the model)

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+			UB_FREQ_F	NMODES_F	SPID_F	GPRC

Optional continuation lines for preload definition

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	PRELOAD	SPCID	PLSID

Optional continuation lines for LOAD SET definition

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	LOADSET	USETYPE	LSID1	LSID2	LSID3

Optional continuation lines for DMIGDV definition

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
+	DMIGDV	S	OUTOPT	NMODE	DVKUPFAC	DVGEUP	DVBUP

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
CMSMETH	5	CBN	1000	200	100000
+			600	100	200000

Field	Contents
CMSID	CMSMETH identification number. (Integer > 0)
METHOD	Component Mode Synthesis method to be employed. See comment 2. No default (Character = CB, CC, CBN, GM, or GUYAN)
UB_FREQ	Upper bound frequency for the eigenvalue analysis for the structural part. If 0.0 or blank, no upper bound is used. See comments 3 and 4. Default = blank (Real > 0.0, or blank)
NMODES	Number of modes to be extracted from structural eigenvalue analysis. If set to -1 or blank, number of modes is limitless. See comments 3 and 4. Default = blank (Integer > -1, or blank)
SPID	The starting SPOINT ID to be used in DMIG matrix output for the structural eigenmodes. No default. See comment 6.
SOLVER	The eigenvalue solver. Either blank or LAN for Lanzos. AMSES for AMSES. Default = LAN (Character = LAN, AMSES, or blank)
AMPFFACT	AMSES Amplification Factor. The substructure modes are solved up to the frequency of AMPFFACT*V2. Higher values of AMPFFACT will lead to more accurate results and longer running times. See comment 9. Default = 5.0 (Real or blank)
SHFSCL	For vibration analysis, it is the estimate of the frequency of the first flexible mode. See comment 12. Default = blank (Real or blank)
UB_FREQ_F	Upper bound frequency for the eigenvalue analysis for the fluid part. If 0.0 or blank, no upper bound is used. See comments 3 and 4. Default = blank (Real > 0.0, or blank)
NMODES_F	Number of modes to be extracted from fluid eigenvalue analysis. If set to -1 or blank, number of modes is limitless. See comments 3 and 4. Default = blank (Integer > -1, or blank)
SPID_F	The starting SPOINT ID to be used in DMIG matrix output for the fluid eigenmodes. No default. See comment 6.
GPRC	Grid participation recovery control. Allows fluid-structure interface grid shape data (that is the modes associated with the fluid-structure interface) to be calculated and stored with the external superelement. Only applicable when GM (general modal formulation) is input in the METHOD field and when all boundary degrees-of-freedom are free (BNDFREE). If any boundary degrees-of-freedom are fixed and GPRC is set to YES, the program will be terminated with an error. Default = NO (YES or NO)
PRELOAD	Flag indicating that a preload will be used in the CMS analysis. See comment 21.
SPCID	SPC SET ID for the preload
PLSID	LOAD SET ID for defining the preload.
LOADSET	Flag indicating that static loads will be reduced in CMS superelement generation run. See comments 11 and 19.
USETYPE	RESVEC/REDLOAD/BOTH defines the type for the static loads reduction. RESVEC – the loads defined on the LSIDi fields are used for generating residual vectors to improve the modal space. REDLOAD – the loads defined on the LSIDi fields used for generating reduced loads. BOTH – both RESVEC and REDLOAD options are selected. Default = BOTH (Comments 11 and 19)
LSIDi	The static load IDs for generating residual vectors and/or reduced loads.
S	Selects the structural part of the model. See Comment 25. Default = S
DMIGDV	Flag indicating that an ASCII file containing CELAS4 and CDAMP3 element data and/or their corresponding design variable definitions is generated for DMIG (Comment 13).
OUTOPT	Defines how design variable definitions are written for DMIG. See comments 13 to 17. 1 – Only CELAS4 and CDAMP3 element data and PDAMP properties (if any) are written. Design variable definitions are not written. 2 – All data from Option-1 and design variable definitions are written (Default, see Comment 14). 3 – All data from Option-2 and constraint (f1<f2) creation data are written (Comment 15). If OUTOPT field is blank, then Option-2 is the default.
NMODE	Defines the number of design variables for ΔK/ΔGE and ΔB in CELAS4 and CDAMP3. See comment 18. If NMODE > 0, the “NMODE” number of design variables will be written to control the first “NMODE” eigenvalue changes (ΔK), damping coefficient changes (ΔGE) and scalar damping value changes (ΔB). If NMODE is not specified (the NMODE field is blank), then as many design variables as the total number of modes are written.
DVKUPFAC	Used to determine the upper bound of ΔK (which is (maximum eigenvalue)*DVKUPFAC). If DVKUPFAC is not specified (DVKUPFAC field is blank), by default it is set to 0.1 (Comment 16). Default: DVKUPFAC=0.1
DVGEUP	Upper bound of ΔGE. This applies to all the design variables for ΔGE. If DVGEUP is not specified (DVGEUP field is blank), by default it is set to 2DVBUP (Comment 16). Default: DVGEUP=2DVBUP
DVBUP	Upper bound of ΔB. This applies to all the design variables for ΔB. If DVBUP is not specified (DVBUP field is blank), by default it is set to 0.4 (Comment 16). Default: DVBUP=0.4

Comments

1.	This definition will be ignored unless referenced in the I/O Options section by a CMSMETH run control.

2.	Several methods are available for Component Mode Synthesis, these are: CB, CC, CBN, GM and GUYAN (see descriptions below).

The first two methods (CB and CC) are used for generating flexible bodies for use with multi-body dynamics analysis software, such as Altair’s MotionSolve.

The remaining methods (CBN, GM and GUYAN) are used primarily to generate external superelements (stored in DMIG format) for use in subsequent finite element analyses.

Flexible body methods:

CB – Craig-Bampton formulation

CC – Craig-Chang formulation

External superelement methods:

CBN – Craig-Bampton Nodal formulation

GM – General Modal formulation

GUYAN – GUYAN reduction:

GUYAN is the same as CBN without including structural eigenmodes; when GUYAN is used, UB_FREQ & NMODES are ignored.

3.	UB_FREQ, NMODES, UB_FREQ_F and NMODES_F cannot all be blank. Additionally, when structural elements are present in the model, UB_FREQ and NMODES cannot both be blank, and when fluid elements are present in the model, UB_FREQ_F and NMODES_F cannot both be blank.

4.	When UB_FREQ = 0.0 and NMODES = 0, this is a special case where no structural eigenmodes will be included in CMS mode generation. If both UB_FREQ and NMODES are specified, lowest NMODES below UB_FREQ will be accepted as structural SPOINTs. Similarly things are applied to fluid part.

5.	If PARAM, EXTOUT, DMIGPCH (or DMGBIN) is defined when using the CB method, a DMIG matrix corresponding to the reduced stiffness and mass matrices will be output. The stiffness and mass corresponding to the eigenmodes will be assigned to the generated SPOINTs.

6.	The SPOINT IDs of the structure and fluid should have distinct IDs. Any fluid SPOINT ID cannot be in between structural SPOINT IDs.

7.	When PARAM,EXTOUT is used to output DMIG matrices, then it is possible to disable the output of a flexh3d file by specifying “OUTPUT,H3D,NONE” in the input file.

The nodal flexh3d file output from the CBN method can be used as the DMIG input (using ASSIGN,H3DDMIG). In this way, the model set output in flexh3d file will be recovered as the interior points of the DMIG matrix in the residual structure run. The displacements of these interior points will be included in the output.

AMPFFACT is used to increase the accuracy of the eigenvalue and eigenvectors at the expense of slightly longer run times. It is recommended to use higher values of AMPFFACT for solid structures like engine blocks and suspension components. If AMPFFACT is not specified by you and the model contains a large number of solid elements, the value of AMPFFACT is automatically reset to 10.

10.	The mass properties of the super element (Mass, Center of Gravity, and Moments of Inertia) are written to the H3D file. In the residual run, these mass properties are included in the mass properties of the structure printed in the .out file.

11.	Static load reduction is supported for CMSMETH superelement generation runs (METHOD=CBN/GUYAN) and Flexbody generation runs (METHOD=CB/CC). Static load reduction is not supported for GM superelement generation runs.

12.	A specification of SHFSCL may improve the performance of a vibration analysis.

13.	If the DMIGDV optional continuation card is defined, a text file (ASCII) filename_dmig_dv.inc is created after the run. This file can be included in the original input deck to study how changes in the eigenvalues/damping of superelements affect the performance of the residual structure.

14.

In addition to the data included in option 1, the ASCII file now also contains design variable definitions. These design variables can control available eigenvalues, structural damping, and viscous damping of the superelement. You can set up an optimization problem by including this file in the original input deck.

15.	In addition to the data included in option 2, the ASCII file now includes data required for the creation of constraints. These constraints ensure that the eigenvalue of the nth mode is less than the eigenvalue of the (n+1)th mode during optimization.

16.	The lower bound of ΔK, ΔB and ΔGE is set such that K, B and GE are always greater than or equal to zero.

17.	The DMIGDV continuation line works only for METHOD = GM (General Modal formulation) in field 3 of CMSMETH (See comment 2).

18.	Where, ΔK, ΔGE and ΔB represent increments/decrements to the eigenvalues (K), damping coefficients (GE) and scalar damping values (B), respectively. It is required to include the .h3d file containing the values of K, GE and B using ASSIGN, H3DDMIG.

19.	The LOADSET flag is required only for the first continuation line. Multiple continuation lines with LSID’s do not require the LOADSET flag.

20.	For further information on creating flex bodies for third party software, refer to Coupling OptiStruct with Third Party Software in the User’s Guide.

21.	Preloading for Component Mode Synthesis subcases can now be defined using the STATSUB(PRELOAD)=SID command. This is more versatile than the PRELOAD continuation line, as any static subcase can be applied as a preload.

22.

SDAMPING cannot be included in the generation of CMS superelements. SDAMPING can be included in the generation of CDS superelements (CDSMETH entry). If you used SDAMPING in the generation of the combined CDS and CMS (METHOD=GM) superelements, the SDAMPING will be included only in the CDS superelement. Use DMIGMOD to apply SDAMPING in the residual run to the CMS (METHOD=GM) superelements. If SDAMPING is not required for CMS superelements in the residual run, then the corresponding DMIGMOD data can be excluded from the model.

23.	CMS runs are not supported, if Frequency-dependent materials are present in the model.

24.	PUNCH output files generated from CMS runs contain ASET, BSET, and CSET information and their corresponding grid and coordinate systems along with the SPOINTs corresponding to the structural eigenmodes.

25.	Currently, the fluid part of the model cannot be selected for the DMIGDV continuation line on the S field.

26.	This card is represented as a loadcollector in HyperMesh.

CMSMETH

CMSMETH

CMSMETH

Optional continuation lines for DMIGDV definition

Comments

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