Week 5

3D Meshing of Rearview Mirror using Tetra element

• Aim

Create a volume mesh ( using Tetra element) on the rearview mirror model under the given element quality criteria and avoid any kinks and dips on the surface of the component.

steps involved for generating a Tetra mesh on the component are,

1) Geometry checks and Geometry cleanup.

2) Generate surface mesh ( with Tria elements) on the model with given element quality criteria.

3) solve the OFF elements for the meshed surface.

4) Define a volume in Volume mesh deck.

5) Mesh the volume with Tetra Rapid or Tetra FEM algorithm.

6) solve the OFF elements for volume meshed component ( that is Tet collapse in the case of volume mesh )

• PROCEDURE

After opening the model, set the perimeter length as 1 mm using Mesh module-> Perimeters-> Length, to refine the perimeters of the component and apply a Topo operation to the entire model, go to Topo Module -> Faces-> Topo.

then orient the faces of the component using Topo module -> Faces -> Orient.

fig. 1- Before faces orient. fig.2- After faces orient.

1. Geometry checks and Geometry cleanup.

checks for geometrical errors in the model by using Tools -> checks-> Geometry.

you can fix most of the geometrical errors by auto fix, select all the errors by cntrl+A then right-click and apply fix

2. Surface meshing with tria elements

After geometrical cleanup and defeaturing, we can move on to surface meshing of components with tria elements.

Before meshing we have to enter Element quality criteria and Mesh parameters.

Go to, Mesh module-> Mesh Generation-> Spot Mesh, choose element type as tria, ortho tria. In order to capture the curved surface better, we can mesh the curved surface with ortho tria elements. but the computational time for ortho tria element is much higher, so we have to use tria elements for flat surfaces.

3. Solve the OFF elements for the surface mesh

In order to see the OFF elements, switch to Hidden mode, OFF elements in the case of surface mesh will be elements failing for minimum and maximum length criteria. To clear the OFF elements we can use Mesh module-> Shell mesh -> Reconstruct.

4. Define a volume and Mesh the volume with Tetra element

After solving all off elements in the surface mesh, we can move on to volume mesh. First define a volume , go to Volume mesh deck -> Volumes -> Define -> Manual , select the entire meshed model, and middle click to confirm -> Property window opens, we have to creates a new P-Solid property.

We can check the volumes created in, Volume Mesh -> Volumes -> Lists.

To mesh the volumes created, right-click on the unmeshed volumes in the Lists, and apply Remesh -> choose Tetra Rapid or Tera FEM algorithms.

or go to volume Mesh-> Unstructured Mesh -> Tera Rapid/ Tetra FEM

5. Solve the OFF elements in Volume Mesh

To check the OFFelements in volume mesh switch to Hidden mode, Off elements in the case of volume Mesh are elements failing for Tet collapse,

To solve the Tet collapse automatically, First isolate failed elements and then apply Fix Quality, ( Volume Mesh -> Improve -> Fix Quality )

In order to solve the Tet collapse without disturbing the surface quality, we have to opt for manual method, go to Mesh Module -> Grids -> MV Free.

select a node that can be moved so that height of the Tetra element can be increased, nodes on the surface should not be moved.

• Final meshed Rearview mirror model

• Learning outcomes
• Learned to check geometry and perform geometry cleanup of the model
• Learned how to create a surface mesh on the component with tria elements, and how to solve the off elements for the surface mesh with given element quality criteria
• Learned how to Define a volume and assign a p-solid property to the volume created.
• Learned how to generate a volume mesh on the model using Tetra Rapid / Tetra FEM algorithms.
• Learned how to solve OFF elements (Tet collapse) for the volume mesh generated.

• CONCLUSION

Successfully generated a volume mesh ( with Tetra element) on the Rearview mirror model with zero Off elements, Tet collapse errors in the volume mesh are solved and there are no kinks or raised edges present on the surface.