G'day, I'm a beginner to ANSYS, and I met a strange problem.
The centroid of my cylinder, which should be at (0,0,-150), can't be the same position in Mechanical (as pic shown). I imported the .iges into "Geometry", and clicked "Model" to open Mechanical, then I checked the properties box and found this problem. But opening SpaceClaim to check it, its position is correct. Hmm...what happened? :(
I tried other types of file(.sat, .obj, .step), but the problem is still unsolved. (by the way, I created the geometry with Fusion 360)
Does anyone know the reason and how to solve it?
Hope someone can help me out, thank you.
#CFD #ANSYS
Hi Milne Ciou,
It appears to be a numerical rounding issue. 2.8e-16 is a very small value which is effectively considered as zero. That's why SpaceClaim rounds it to 0. Have you checked the *.iges file? Is the position value exactly 0.0 mm? You can open the file with a simple text editor and check the text. More importantly, is this small deviation significant for your model? I mean 1e-16 mm is less than 1 nanometer.
Sincerely,
Pavlo
The centroid of a geometry is the point at which the geometry is balanced. In ANSYS Mechanical, the deviation of the centroid can occur due to several factors such as mesh density, element quality, and material properties. To solve this issue, you can try the following steps:
Refine the Mesh: Increasing the mesh density will give a more accurate result, as the elements will be smaller, and the geometry will be represented more closely.
Check Element Quality: Make sure that the elements in your model are of good quality. Poor quality elements can lead to inaccurate results.
Verify Material Properties: Ensure that the material properties used in the model are accurate. Incorrect material properties can also lead to deviation in the centroid.
Check Geometry: Verify that the geometry is accurate and that it is properly defined. If the geometry is not accurate, it can lead to deviation in the centroid.
Try using different type of element: Different type of elements like Solid, shell, beam etc can give you different centroid results.
Use the Move/Copy feature: In ANSYS Mechanical, you can use the Move/Copy feature to adjust the position of the centroid if necessary.
By following these steps, you should be able to reduce the deviation of the centroid in ANSYS Mechanical. However, keep in mind that some deviation might always be present due to the numerical approximations used in FEA.
Pavlo Pavliuchenko Hi,
Oh, I wasn't aware that it's smaller than a nano; in my model scale, the deviation is small enough to be ignorable. It's just not satisfying. Hmm, if it's a common defect of Mechanical, maybe just accept that.
Thanks for your reply!
Ahmad Bilal Hi,
But I checked the property before generating the mesh, so I think the deviation is irrelevant to its mesh. I also tried building geometry with SolidWorks; I found different types of files(.obj, .step, .sat) have different values of deviation. Thus, I'm sure that no problem with my geometry.
Thanks for your enthusiastic reply! Oh btw, is it possible that I can adjust the magnitude of "standard Earth gravity" in Mechanical? (for simplification, I just want it to be 9.8m/s^2.)
The deviation in the centroid position of your cylinder could be due to several factors, including the modeling software used to create the geometry, the file format used for import and export, and the software settings used for analysis.
Here are some suggestions that you could try to resolve the issue:
Check the file format: The .iges file format is known to have some limitations in preserving the geometry details, which could result in deviation of the centroid. You could try importing the file using other file formats, such as .sat, .obj, or .step, to see if that resolves the issue.
Export the geometry with high accuracy: When exporting the geometry from Fusion 360, ensure that the highest level of accuracy is selected. This can help maintain the geometric details of the model and reduce the deviation of the centroid.
Check the software settings: The settings used in ANSYS Mechanical could also contribute to the deviation of the centroid. Check the settings for geometry import, mesh generation, and analysis to see if they could be affecting the accuracy of the results.
Verify the results: Verify the results by comparing them with experimental data or other reliable sources to validate the accuracy of the solution.
If the deviation of the centroid still persists, it may be necessary to revise the model or consider using a different numerical method to solve the problem.
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