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vk.com/club152685050C ponent Mode Synthesis| vk.com/id446425943

Step

Description

Command(s)

 

 

 

 

 

RSTOFF,ELEM,10000

 

Expand and solve.

EXPSOL,1,4

 

 

SOLVE

 

 

FINISH

6.

Read the results.

 

 

Specify the superelement matrix file

/CLEAR,NOSTART

 

containing the results.

 

 

 

/POST1

CMSFILE,ADD,PART1,RST

CMSFILE,ADD,PART2,RST

CMSFILE,ADD,PART2SYM,RST

...

...

11.3.10. Example: Reduce the Damping Matrix and Compare Full and CMS Results with RSTMAC

This section demonstrates how to introduce damping in the tuning fork model described in Example Component Mode Synthesis Analysis (p. 290). RSTMAC is then used to compare complex results obtained by the full and CMS models. The procedure is as follows:

1.The modal analysis is performed for the full model with nodes located at y=0 fixed. Damping is introduced in one zone of part 2 and one zone of part 3 using a material mass matrix multiplier (MP,ALPD) and a material stiffness matrix multiplier (MP,BETD):

/batch,list

/title, 2D Tuning Fork with damping

/filename,fork_full

!Include the geometry, material properties

/input,cms_sample,inp

/prep7

!Fix base

nsel,s,loc,y,0,0

d,all,all

allsel,all

! Damping elements

 

et,2,plane182,,,3

 

r,1,tthk

 

mp,ex,2,190e9

 

mp,dens,2,7.7e3

 

mp,nuxy,2,0.3

 

mp,alpd,2,.1

! Mass matrix multiplier

mp,betd,2,1e-6

! Stiffness matrix multiplier

type,2

 

 

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Example Component Mode Synthesis Analysis

mat,2

esel,s,,,501,652 ! Damped material applied on a zone of part 2 emodif,all

et,3,plane182,,,3

r,1,tthk

mp,ex,3,190e9

mp,dens,3,7.7e3

mp,nuxy,3,0.3

mp,alpd,3,.1 mp,betd,3,2e-6

type,3

mat,3

esel,s,,,781,932 ! Damped material applied on a zone of part 3 emodif,all

allsel,all fini

save

/sol

antype,modal

modopt,qrdamp,8,,,on ! QRDAMP solver is used to extract the complex eigenmodes mxpand,all

solve fini

! Print real and imaginary parts of some modes for nodes 1 to 20

/post1

nsel,s,node,,1,20

set,list

! Print a summary of load step and substeps

set,1,1

! Real part

prdi

 

set,1,1,,2 ! Imaginary part

prdi

 

set,1,4

! Real part

prdi

 

set,1,4,,2 ! Imaginary part prdi

fini

2. The analysis is performed using a CMS analysis with fixed-interface method:

/clear,nostart /filename,fork_cms_fixed

/input,cms_sample,inp

/prep7

! Fix base

nsel,s,loc,y,0,0

d,all,all

allsel,all

! Damping element

et,2,plane182,,,3

r,1,tthk

mp,ex,2,190e9

mp,dens,2,7.7e3

mp,nuxy,2,0.3

mp,alpd,2,.1 mp,betd,2,1e-6

type,2

mat,2

esel,s,,,501,652

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emodif,all

et,3,plane182,,,3

r,1,tthk

mp,ex,3,190e9

mp,dens,3,7.7e3

mp,nuxy,3,0.3

mp,alpd,3,.1 mp,betd,3,2e-6

type,3

mat,3

esel,s,,,781,932

emodif,all

allsel,all save

fini

! Generation pass 1

/filname,part1

/solu

antype,substr

seopt,part1,2,1 ! No damping, only stiffness and mass matrices are reduced cmsopt,fix,10

cmsel,s,part1

cmsel,s,interface1

m,all,all nsle solve fini

save

! Generation pass 2

/filname,part2

/solu

antype,substr

seopt,part2,3,1 ! Stiffness, mass and damping matrices are reduced cmsopt,fix,10

cmsel,s,part2

cmsel,s,interface2

m,all,all nsle solve fini

save

! Generation pass 3

/filname,part3

/solu

antype,substr

seopt,part3,3,1 ! Stiffness, mass and damping matrices are reduced cmsopt,fix,10

cmsel,s,part3

cmsel,s,interface3

m,all,all nsle solve fini

save

! Use pass

/clear,nostart

/filnam,use

/prep7

et,1,matrix50

type,1

 

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Example Component Mode Synthesis Analysis

se,part1

se,part2

se,part3 fini

/solu

antype,modal

modopt,qrdamp,8,,,on ! QRDAMP solver is used to extract the complex eigenmodes mxpand,all

solve fini

/post1

set,list ! Print a summary of load step and substeps after use pass fini

! Expansion pass 1

/clear,nostart

/filname,part1 resume

/solu

expass,on

seexp,part1,use

numexp,all ! All solutions are expanded solve

fini

! Expansion pass 2

/clear,nostart

/filnam,part2 resume

/solu

expass,on

seexp,part2,use

numexp,all solve

fini

! Expansion pass 3

/clear,nostart

/filnam,part3 resume

/solu

expass,on

seexp,part3,use

numexp,all solve

fini

! Print real and imaginary parts of some modes for nodes 1 to 20

/clear,nostart

 

/post1

 

cmsfile,add,part1,rst

 

set,list

! Print a summary of load step and substeps after expansion pass

cmsfile,add,part2,rst

 

cmsfile,add,part3,rst

 

set,1,1

! Real part

nsel,s,node,,1,20

 

prdi

 

set,1,1,,2

! Imaginary part

prdi

 

set,1,4

! Real part

prdi

 

set,1,4,,2

! Imaginary part

prdi

 

cmsfile,clear

 

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fini

3. Real and imaginary parts of the eight modes are appended and written in file fork_cms_fixed.rst:

/clear,nostart /filname,fork_cms_fixed

resume,,, fini

/post1

*do,j,1,8

!Append the real part of the 3 substructures file,part1

append,1,j,,

file,part2

append,1,j,,

file,part3

append,1,j,,

!Write the appended real part in the result file

!"1" indicates that complex results are written

reswrite,fork_cms_fixed,,,,1

!Append the imaginary parts of the 3 substructures file,part1

append,1,j,,1

file,part2

append,1,j,,1

file,part3

append,1,j,,1

!Write the appended imaginary part in the result file

!"1" indicates that complex results are written

reswrite,fork_cms_fixed,,,,1 *enddo

4.Finally, eigenmodes of the full model (fork_full.rst) and eigenmodes of the CMS model after expansion (fork_cms_fixed.rst) are compared using the RSTMAC command:

rstmac,fork_full,1,all,fork_cms_fixed,1,all,,,,2 fini

The results show good agreement:

****** Modal Assurance Criterion (MAC) VALUES ******

 

 

 

 

 

Solutions

are complex

 

 

 

 

Rows:

8 substeps in load step

1 from file fork_full.rst

Columns:

8 substeps in load step

1 from file fork_cms_fixed.rst

 

1

2

3

4

5

6

 

7

8

1

1.000

0.000

0.000

0.000

0.000

0.000

0.000

0.000

2

0.000

1.000

0.000

0.000

0.000

0.000

0.000

0.000

3

0.000

0.000

1.000

0.000

0.000

0.000

0.000

0.000

4

0.000

0.000

0.000

1.000

0.000

0.000

0.000

0.000

5

0.000

0.000

0.000

0.000

1.000

0.000

0.000

0.000

6

0.000

0.000

0.000

0.000

0.000

1.000

0.001

0.000

7

0.000

0.000

0.000

0.000

0.000

0.001

1.000

0.000

8

0.000

0.000

0.000

0.000

0.000

0.000

0.000

1.000

*** NOTE ***

 

 

 

CP =

0.000

TIME= 00:00:00

Solutions matching in RSTMAC

command

succeeded.

 

 

 

 

8 pairs of solutions have a

Modal Assurance Criterion (MAC) value

greater than the smallest acceptable

value (.9).

 

 

 

 

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Example Component Mode Synthesis Analysis

********************************** MATCHED SOLUTIONS **********************************

Substep in

Substep in

MAC value

Frequency

Frequency

fork_full.rst

fork_cms_fixed.rst

 

difference (Hz)

error (%)

1

1

1.000

-0.49E-06

0.0

2

2

1.000

0.15E-06

0.0

3

3

1.000

-0.17E-02

0.0

4

4

1.000

-0.23E-05

0.0

5

5

1.000

-0.13E+00

0.0

6

6

1.000

-0.13E+00

0.0

7

7

1.000

-0.36E-03

0.0

8

8

1.000

-0.14E-01

0.0

Note

If you repeat the whole process, you must delete previous .RST files to avoid appending results of the new analysis to the previous file. The following commands can be used in this case:

/inquire,test,exist,fork_full,rst *if,test,eq,1,then /delete,fork_full,rst

*endif /inquire,test,exist,fork_cms_fixed,rst *if,test,eq,1,then /delete,fork_cms_fixed,rst

*endif

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