Learning Forum

[castrohenrique0208]

Hi everyone,

I’m trying to simulate a constraining layer design consisting of three layers: one layer of composite material, one layer of viscoelastic material, and one layer of an aluminum plate.

I’ve read almost every discussion on this topic, but nothing has helped so far. I found an ANSYS document and video and tried to replicate the steps, but the problem remains unresolved. I have experimental data for the viscoelastic material( storage modulus and loss factor).

I'm using ANSYS Workbench and inputting the viscoelastic properties through a snippet command, but I keep getting the following message from ANSYS:

For material 2, the harmonic viscoelastic model requires two elastic constants. The shear modulus experimental data will be used with the real Poisson's ratio input via the MP or TB,ELAST command, and the imaginary part of Poisson's ratio will be set to zero.

I also tried switching to APDL and curve-fitting my data, but I encountered an error (figure 1).

I have this university project due by Saturday, 7th September. Can anyone help me understand what I might be doing wrong?

I’m attaching some pictures and the project files for reference.

https://drive.google.com/file/d/1Ydu3UY5QfyiOYddeTG1R1v5Aod7wCV8u/view?usp=drive_link

 

[benjamin.starling]

Hi Henrique,

In the following section:

MAPDL Help -> Material Reference -> 4.8.3.1.2 Experimental Data Complex Modulus

Towards the bottom:

Two elastic constants are required to define the model. If only one set of experimental data is defined, the poisson's ratio is used as the second elastic constant.

You can add the following to your command snippet.

    MP, PRXY, MATID, 0.3   ! 0.3 being the possions ratio for your material

Alternatively you can use the TB command, or add bulk modulus, tensile modulus, or possions ratio as experimental data.

If this doesn't remove the error, can you please add screenshots of your material definition in engineering data and mechanical showing the command snippet implementation.

[castrohenrique0208]

Hi Benjamin, 

Thank you for your reply. 

 

I have tried before by adding (MP, PRXY, MATID, 0.45) to my command snippet, but I get the same message as in figure 2 (above). 

 

For the viscoelastic material I have the density and isotropic properties. 

[benjamin.starling]

Hi Henrique,

I wasn't able to view your project as no files were included, just the .wbpj file. I have recreated a simple problem as per the screenshots below. This solves just fine in 2024R1.

 

[castrohenrique0208]

Hi Benjamin,

I apologize for forgetting to send my files, I made a mistake.

I saw your answer on the forum and I have a question. Does your model account for the viscoelastic variation according to the snippet command? Also, could you verify if it doesn't show the following message in the solution information:

For material 2, the harmonic viscoelastic model requires two elastic constants. The shear modulus experimental data will be used with the real Poisson's ratio input via the MP or TB, ELAST command, and the imaginary part of Poisson's ratio will be set to zero.

When I run my model, it doesn't account for the snippet command, but it still runs. However, the results are incorrect, when comparing with the simulation without the viscoelastic material.

 

[benjamin.starling]

Hi Henrique,

The viscoelasticity can be turned off per analysis system with the command snippet shown below. If the material has multiple tables, be sure to issue the correct Label(s) on the TBDELE command. You can also modify the material per analysis be reissuing the TB and TBPT commands

Below is the comparison of the model with and without the visoelastic material table. First is phase angle of the response at a single location, the second is the amplitude. My model shows very little sensitivity to the visco material, but that is because my model was made up just to test implementation.

When I soften the visoelastic properties by a factor of 100 I get the following comparison.

If you are not getting the expected results, there is something else wrong with the model or material setup. Please upload an archived workbench project, and provide more information about the expected results, if you would like me to investigate further.

 

[GAURAV SHARMA]

you can follow these paper. a detailed process related to the use of viscoelastic material for constrained layer damping in ANSYS. 

http://dx.doi.org/10.1002/pen.26696

http://dx.doi.org/10.4028/p-MRpjE3