Volume Meshing on a Rearview Mirror in ANSA Preprocessor

Aim: To mesh a 'rearview mirror' using tetra elements without having any kinks and Dips on the surface. Removing geometrical errors and meshing the component with the given quality criteria for the elements, is of prime importance.

S.No	Quality Criteria	Value
1	Target/Average length	1
2	Minimum Length	0.5
3	Maximum Length	2
4	Tetcolapse	0.2

Procedure: The operation that has to be performed here is volume meshing or solid meshing or 3D meshing. This is achieved by deploying a 2Dmesh on the surface first. Following which volume is to be assigned in the volume mesh module by creating new solid PID, and then deploying a volume mesh on this new solid. Volume meshing has two types of meshing methods. Structured mesh is where hexa mesh is created and unstructured mesh is where tetra mesh is created. For this component the meshing elements in the volume should be tetrahedral, so we proceed with the unstructured meshing method.

Starting with the topology cleanup, topo is performed on the imported component first. It is followd by geometry check and then elimination of errors found in the geometry. The difference between the imported geometry and the cleaned geometry is shown in the images below.

Next step would be to remove extra lines (cuts) from the surface. These are the lines due to which the elements may fail for minimum length criteria. Removing such lines proves efficient way of generating surface mesh without any failures.

Generation of surface mesh needs more attention as selecting the type of elements to be deployed is important for accuracy and efficiency. The ortho tria elements can capture curved surfaces very accurately but they take more time for solving than the simple tria elements. So, on the straight surfaces simple tria mesh is deployed and ortho tria is deployed on the curved surfaces. After generation of surface mesh, quality of it is checked and failing elements are rearranged.

Now proceed to the volume mesh module and firstly define the volume that is to be meshed by creating a solid PID for the part. When created, right clicking the new volume will drop a window where 'Remesh' option will be available. By selecting it, a new window will ask for the type of mesh to be created. Ttra Rapid and Tetra FEA are the two types for structural analysis. They differ only in the way of approaching the elements from the surface to centre. Also, Tetra FEA can create a pyramid element for any quad element present on the surface mesh, and then begin for tetrahedral from there onwards. Though a window will appear showing the pyramid element warning. Selecting any of the two will give a volume tetra mesh.

Finally the meshed volumes are to be seperated from the Geometry by the release option in the volume mesh module. This release will give the FEA of the model which is further the main part to be solved. Also, after creating the FEA it cannot be rearranged for any flaws in it. Releasing the FEA from the volume and geometry is the last step which gives FEA.

This was the detailed procedure for volume meshing any component. Though the way for proceeding depends on individuals. In this part there are four PIDs already set.Approaching one PID at a time from geometry clean up till volume mesh and then proceeding for next PID is the way I prefer to work.

Learning Outcomes: Using unstructured mesh for volume meshing for tertahedral elements is a new exploration. Handling trias is totally different in volume mesh than in the surface mesh and midsurfacing methods.

Conclusion: The rearview mirror is meshed successfully by removing all the geometrical errors and by satisfying all the quality criterias given.

The link for downloading the meshed model is given below.

https://drive.google.com/file/d/1q86CZgvUT2o3da0xCDUc-pqsXxizJG9h/view?usp=sharing