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Problem of extracting structural damping

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Posts: 5
Topic starter
(@PeterC)
Active Member
Joined: 15 years ago

Hello,

I have a problem of extracting structural damping coefficient of a sandwich plate type steel / polymer / steel. I have already entered the shear modulus of the polymer in ABAQUS G = G0 (iw) / (1 + iw) With the: *viscoelastic, frequency=TABULAR

I do not know if my approach is right?

My inp file has this form:

*NODE, NSET=ALLNODES, SYSTEM=R

..

*ELEMENT, TYPE=S4 , ELSET=THIN-SHELL1

..

*SHELL GENERAL SECTION,

ELSET=THIN-SHELL1 ,

COMPOSITE

0.000762,3,Mat_COUCHE-1-3

0.000254,3,Mat_COUCHE-2

0.000762,3,Mat_COUCHE-1-3

*MATERIAL,NAME=Mat_COUCHE-1-3

*ELASTIC,TYPE=ISOTROPIC

68.9E+9, 0.3

*DENSITY

2740.0,

*MATERIAL,NAME=Mat_COUCHE-2

*viscoelastic, frequency=TABULAR

29966703.66 , 998890.1221 ,,, 30

59983337.96 , 999722.2994 ,,, 60

..

*DENSITY

999.0,

*ELSET, ELSET=ALLELEMENTS

THIN-SHELL1 ,

*BOUNDARY

*STEP,INC=10

*FREQUENCY, EIGENSOLVER=LANCZOS

20

*MODAL DAMPING,MODAL=COMPOSITE

1,20

*MODAL FILE

*MODAL PRINT,FREQUENCY=1

*END STEP

**

Thank you for your help

3 Replies
Posts: 3998
(@jorgen)
Member
Joined: 4 years ago

What happens if you try to run the inp-file?

3 Replies
Posts: 5
Topic starter
(@PeterC)
Active Member
Joined: 15 years ago

The frequency result is good, but the damping have not.

And I have this WARNING message in . Dat:

***WARNING: SHELL GENERAL SECTION WILL USE ONLY THE ELASTIC PART OF THE

MATERIAL DEFINITION TO COMPUTE THE SHELL STIFFNESS TO BE USED

THROUGHOUT THE ANALYSIS.

*STEP,INC=10

*STEP,INC=10

*STEP,INC=10

*FREQUENCY, EIGENSOLVER=LANCZOS

*FREQUENCY, EIGENSOLVER=LANCZOS

*MODAL DAMPING,MODAL=COMPOSITE

*END STEP

*BOUNDARY

*STEP,INC=10

*FREQUENCY, EIGENSOLVER=LANCZOS

*FREQUENCY, EIGENSOLVER=LANCZOS

*MODAL DAMPING,MODAL=COMPOSITE

***WARNING: *MODAL DAMPING WILL BE IGNORED IN NON MODE-BASED AND STEADY STATE

DYNAMICS, SUBSPACE PROJECTION PROCEDURES. INSTEAD, SPECIFY DAMPING

WHEN DEFINING MATERIALS OR BEHAVIORS (*DAMPING, *CONNECTOR

DAMPING, *VISCOELASTIC, *DASHPOT).

*MODAL FILE

*MODAL PRINT,FREQUENCY=1

***WARNING: THE FREQUENCY PARAMETER IS IGNORED IN A *FREQUENCY OR *BUCKLE STEP

*END STEP[/SIZE]

Reply
Posts: 3998
(@jorgen)
Member
Joined: 4 years ago

I recommend that you try to validate your model by running a single polymer layer. That way you can hopefully better isolate the problem.

-Jorgen

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