## General Mechanical

#### Solar panel flying off modal simulation

• Jedi_USC
Subscriber

Hello,

I am working on a student project to design a satellite.

In the picture below you can see the areas where the solar panel will be connected to the structure.

The panel is connected from the top and bottom to the chassis using a fixture and at the center using a screw.

I used the a bonded connection between the two lines shown below

Then I added a screw to hold the panel to the chassis in the center

But the whole thing comes off in the simulation:

I think it stems from a misuse of boundary conditions. Any suggestions? How would you do things differently?

• Sandeep Medikonda
Ansys Employee

Hi Jedi,

The bonded contact at the bottom seems to hold fine, correct? It is not clear to me if bonded contact is being defined at the very top as well?

I see that you are defining bonded contact at the bottom and at the screw, but I think you might be missing it at the top. Can you confirm this?

Regards,

Sandeep

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• Jedi_USC
Subscriber

Hi Jedi,

The bonded contact at the bottom seems to hold fine, correct? It is not clear to me if bonded contact is being defined at the very top as well?

I see that you are defining bonded contact at the bottom and at the screw, but I think you might be missing it at the top. Can you confirm this?

Regards,

Sandeep

I was on vacation, but now that I'm back, let me check.

• Jedi_USC
Subscriber

It is bonded at the top, but the difference is that the bottom connection is between two coincident lines, whereas the top connections the line / geometry does not intersect, and the lines are parallel. All is bonded.

And the screw area is still disconnecting.

• Sandeep Medikonda
Ansys Employee

Can you first look at what visualization scale factor you are looking at this? Set it to true scale?

If that doesn't help. Can you show the details of the top bonded contact and illustrate how they are defined with the help of an image?

Regards,
Sandeep

• Jedi_USC
Subscriber

Thanks.

Where can I find the visualization scale factor?

• Jedi_USC
Subscriber

I changed the geometry and now there is no separation between the solar panel and the chassis.

• Jedi_USC
Subscriber

In addition to the three contact regions I showed in my first post:

I added another frictional contact because the solar panel has the option of sliding across the middle surface, shown in blue:

I ran simulation with and without this contact.

With a frictional contact:

With no friction contact:

For the simulation with the friction contact, I get the warning:

"One or more Remote Boundary Conditions have been scoped to a solid vertex.  Stiff beams have been employed to connect the remote point to the vertex.  Check results carefully. You may visualize the created beams on the Solution Information Folder."

Without the friction contact, I get the same warning.

Any thoughts as to what is causing this error, and as to the quality of this simulation?

• Sandeep Medikonda
Ansys Employee

Modal analysis is a linear analysis. So all contacts are either converted to no separation or bonded contacts (i.e., only linear contacts are used).

This looks like just a warning and based on what it says, looks like it has to do with the way you are scoping something. If you right click on the warning and use Go to Object, it will take you to the object that is causing this warning. If you think you have set up the simulation correctly, you can ignore the warning.

Regards,
Sandeep

• Jedi_USC
Subscriber

When I click "Go to Object", it takes me to the solution folder.

• Sandeep Medikonda
Ansys Employee

Again, this is not an error and just a warning. Typically:

Remote boundary conditions scoped to a large number of elements can cause the solver to consume excessive amounts of memory. Point masses in an analysis where a mass matrix is required and analyses that contain remote displacements are the most sensitive to this phenomenon.

You can visualize the beams that the warning is referring as shown here:

This will show you something like this for all the beams connecting to the point mass in your model:

If this looks correct to you in your model, you can ignore that warning.

Regards,
Sandeep
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• Jedi_USC
Subscriber

It looks ok, I think. I'm not sure what I'm looking for, some unusual behavior?

Screenshot:

• Jedi_USC
Subscriber

Also, I added another solar panel with a hinge to the model, but I am unsure if the connections I created are correct. I defined a "no separation" contact between the hinge rod and the solar panel bore, as can be seen below:

Should I allow small sliding? What will that accomplish?

• Sandeep Medikonda
Ansys Employee

If they are already touching, no separation will be the same as a bonded contact. See this article by the developer on small sliding. You can try small sliding but I don't think it will make any difference in this particular model.

• Jedi_USC
Subscriber

If they are already touching, no separation will be the same as a bonded contact. See this article by the developer on small sliding. You can try small sliding but I don't think it will make any difference in this particular model.

Thanks!

All of your input is a huge help.

- J

• Sandeep Medikonda
Ansys Employee

Jedi, please close the discussions so that it will help someone else in the future. Take a moment to look at the guidelines.