Learning Forum

[N1129070]

I am currently working on a simulation in ANSYS Workbench involving a coupled field static analysis followed by a coupled field harmonic analysis. I model two piezoelectric actuators near each side of a string. I encountered an issue that I need assistance with.

Problem Description:

• In the first step, I performed a coupled field static analysis where I applied a displacement boundary condition at one end of a string and a fixed boundary condition at the other end (pretension of string). I also applied voltages to the piezoelectric actuators attached to the beam.
• I then linked the solution from this static analysis to a coupled field harmonic analysis setup. I intended for the string to maintain its static displacement while the piezoelectric actuators actuate harmonically.

Issue:

When I check the harmonic analysis results, it appears that the displacement boundary condition from the static analysis is being treated as a harmonic load. As a result, the sting is stretching and shortening in cycles, which is not the intended behaviour. Instead, I want the string to first stretch as per the static analysis and then remain in that state while only the piezoelectric actuators function during the harmonic analysis.

Request for Guidance:

Could you please advise on how to correctly configure the boundary conditions so that the displacement from the static analysis acts as a constant initial condition in the harmonic analysis, without turning into a varying harmonic load?

I selected different options ('keep all', 'keep inertia and displacement constraints', 'keep displacement constraints') in the 'load control' section in the Pre-stress section of coupled field harmonic analysis. But they do not work and still, I see the harmonical movement of string in the z-direction (longitudinal) in the directional deformation results, which is wrong.

please kindly see the attached picture.

I would greatly appreciate any insights or guidance you can provide to resolve this issue.

[dlooman]

I just tried a simple pure structural prestressed full (not mode-superposition) harmonic with an applied non-zero displacement in the static.  The harmonic did not treat this non-zero displacement as a harmonic load.  Could you try a full harmonic?

[N1129070]

thanks for your answer. Yes, I work with the full harmonic. But in my case, the non-zero displacement (in coupled field static) always acts as harmonic load in coupled field harmonic analysis. 

may I send my case to you?

[Erik Kostson]

 

 

Hi

Ansys empl., are not allowed to download any external files.

Set load control to keep all disp. as zero (see image below):

To try that it is OK then – just apply zero voltages everywhere so no electric excitation (all zero) in the coupled harmonic analysis, and then all results should be zero.

If you getting nonzero results with the above recomend., then:

Finally,I have tried it out on myside (similar case as you show), and it works all good in 2024 R2 (I would suggest to download 2024 R2 – latest version).

All the best

Erik