Questions about Structural buckling analysis

[gavin20181001]

Hello everyone,

I would like to ask if the mesh structure can be analyzed

Because I want to substitute the model, but I cannot display the model.

Can someone tell me why? Thanks

model:

https://drive.google.com/file/d/1aeVDUMXiu1q6DRS3Ase1sgH92PP3cKQ5/view?usp=sharing

[John_Holtz · Accepted solution]

Hi @gavin20181001 

I see why you did not attach an image of your model. It is too hard to visualize in a static image! You really need to rotate the model around and zoom in and out to understand what it is. With that said, here are two poor images of the model so that other readers can get an idea of what the model is:

Isometric viewFront view (or any view; they are all the same!)

For lack of a better description, it is a cube. Each side of the cube is a grid (or screen, or grating).

You cannot do a simulation on this model with Fusion. Fusion Simulation only works with solids, and your model is only a surface. You should use a different program, such as Inventor and Inventor Nastran, so that you can analyze the structure using shell elements. (Shell elements have an area but no thickness, just like your model.)

[gavin20181001]

Hi john.holtz,

Thank you for your reply,

I understand that something is wrong with my model.

I currently try to reduce the model units and use the Brep form to

test it and merge all the brep into one in the funsion 360 software.

But analysis is still failed.

model:

https://drive.google.com/file/d/1Q7eO4iB5hnLdA0myeF8ItySBbdqqg5E0/view?usp=sharing

[John_Holtz]

Hi @gavin20181001 

The file that you attached did not have any setup for the simulation. You probably attached a version before you saved the model.

I tried to apply some loads and constraints just to see what would happen. The full error that was returned is as follows. (The image that you attached only showed the last 2 lines. The full message probably included an error similar to what I received.)

"Stiffness Matrix Singular" indicates that the model is not statically stable. The most likely reasons are these:

1. incorrect material properties. (Ha! I forgot to check what materials are used, so that may be the problem in my analysis!! No, it looks like everything is steel.)
2. Contact is not defined, so parts are free to move an infinite distance with any load. (I did define contact, but I think it will not work in this type of model.)
3. Mesh is distorted (usually when it is too large).
4. Components/bodies are not statically stable because of other reasons.

I think the problem is item 4. It looks like the dozens or hundreds of bodies are connected together along a line or edge. In this section view, one body is shaded in blue, and the adjacent body is shaded in green. They "connect" along a line (shown by the arrows). If these two bodies could be connected along the line in the analysis, they would act like a hinge; they would not resist any bending. (Fusion does not have the ability to connect two bodies that only touch along a line, so a line connection will not work.) Is the real design hinged together between every component? I think there needs to be thickness here so that each of the 6 faces act like a plate (a plate with square holes and varying thickness, but other wise continuous and able to resist bending).

Creating some non-zero thickness along these edges would also allow the entire model to be one body. If you have one body that is all connected, you do not need to use contact in the simulation. If you have multiple bodies (whether they are touching or not), you need to use contact in the simulation to connect them together.

Let us know what you find out.