Face normals problem with modal analysis setting for aluminium wheel.

Question

동규 2022-7-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1753665-face-normals-problem-with-modal-analysis-setting-for-aluminium-wheel

回答： Shubham 2023-12-29

forum_2.zip

%%%%%%%%%%%%%%%%% import, mesh %%%%%%%%%%%%%%%%%
structuralmodel = createpde('structural','modal-solid');
importGeometry(structuralmodel,'wheel_modeling_2.stl');
generateMesh(structuralmodel,'Hmax',15)
pdeplot3D(structuralmodel)
%% 
%%%%%%%%%%%%%%%%%%  Modal  %%%%%%%%%%%%%%%%%%%%%%
structuralProperties(structuralmodel,'Youngsmodulus',210E9,'PoissonsRatio',0.3,'MassDensity',8000); %% properties are from help-menu example
structuralBC(structuralmodel,"Edge",4,"Constraint","fixed");
modalResults = solve(structuralmodel,"FrequencyRange",[-1 1200]);

I want to set modal analysis for aluminium wheels. So I import .stl file and converted to geometry with mesh.

But I can't solve the warning "Face normals directed incorrectly. Face normals must point outwards, away from the solid."

How can I handle with it?

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Answer 1

Shubham 2023-12-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1753665-face-normals-problem-with-modal-analysis-setting-for-aluminium-wheel#answer_1379926

Hey 동규,

I understand that you want to perform modal analysis for aluminium wheels for which you have imported a model from a “.stl” file and converted it into a mesh. You wish to resolve the error: "Face normals directed incorrectly. Face normals must point outwards, away from the solid."

The direction of a normal is decided by the ordering of the vertices present in the triangle. The normal vector is obtained by cross product of two edges of a triangle. The convention is to use the right-hand thumb rule to determine the direction of the normal. If the vertices are present in counterclockwise manner, then the direction of normal is outwards. For more information, please refer to this previous MATLAB answer provided by MathWorks Staff: https://www.mathworks.com/support/search.html/answers/321387.html?fq%5B%5D=asset_type_name:answer&page=1

You can try checking the direction of surface normal. Please have a look at the following for plotting and computing mesh normals:

Surfnorm (for plotting surface normal): https://www.mathworks.com/help/matlab/ref/surfnorm.html

COMPUTE_mesh_normals: https://www.mathworks.com/matlabcentral/fileexchange/29585-compute-mesh-normals

To have a consistent direction for all the normals (either inside or outside), you can try referring to the below function “unifyMeshNormals” present in file exchange:

https://www.mathworks.com/matlabcentral/fileexchange/43013-unifymeshnormals

If all the normal point in a consistent direction but are not pointing outwards, you may try reordering the vertices.

Hope this helps!!