Tetra Meshing Of Rear View Mirror

Tetra Meshing Of Rear View Mirror

Aim: To create the tetra meshing for rear view mirror model by eliminating geometrical errors and considering the given element quality criteria using ANSA.

Element Quality Criteria:

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 meshing is done by following steps

1. Import Rearview mirror.IGS in to the ANSA

2. CAD Geometry clean up and topology

3. Defeaturing

4. Ortho tria or tria meshing

5. Volume Define

6. Tetra meshing for volume

7. Check for tetcolapse

1. Import Rear view mirror.IGS in to the ANSA: Import the given Rearview mirror.IGS in to the ANSA Shown in the fig.1.1. Make orientation of all visual faces and change the element length on perimeter to 1 in both perimeters and macros (MESH>Perimeters>Length) show in fig.1.2.

Fig.1.1: Imported File Rearview Mirror.IGS

Fig.1.2: Rearview Mirror

2. CAD Geometry clean up and topology: In this step the given model undergo geometry check (Tools>Checks>Geometry) where ANSA check for any geometrical errors such as collapsed faces, cracks, single con, triple con etc. those errors are shown in fig. 2.1.

Geometrical errors are cleared by using release triple cons and topo, deleting the overlapped faces and creating new faces. Here all geometrical errors auto fixed. Fig.2.2 shows the fixed all Geometrical errors.

Fig.2.1: Geometry Errors

Fig.2.2: Geometry Clean Up

Before going to the mesh check geometrical errors for all individual.

5) Defeaturing: Update the element length as per given element Quality Criteria (Mesh>Perimeters>Length) which is Target/Average length 1. Removing all unnecessary edges, fillet radiuses etc. also maintain distance between two cons or nodes not less than Minimum Length of 0.5.

4. Ortho tria or tria meshing: Assign given element Quality criteria in to the ANSA (Utilities>Quality criteria) and Mesh Parameters (Utilities>Mesh Parameters) shown in Fig.4.1.

Fig.4.1: Mesh Parameters

Here we have selected ortho tria but while doing mesh we can change as per requirement in option list element type. Ortho tria is used where the geometrical features such as holes, curve areas computation time is more compared to normal tria etc. And tria is used at flat faces.

Start meshing Process by Spot Mesh (MESH>Mesh Generation>Spot Mesh>select)

Modify mesh flow using Reconstruct (MESH>Shell Mesh>Reconstruct), Smooth (MESH>Shell Mesh>Smooth). Make sure that while doing mesh all the element Quality criteria mush satisfied. In the 4.1,4.2&4.3.

Fig.4.1: Spot Mesh

Fig.4.2: Spot Mesh

Fig.4.3: Spot Mesh

5. Volume Define: once mesh is done on surface we need to define the volumes for each individual separately. Define volume under (VOLUME MESH>Volumes>Define>manual).

Select each part separately and assign volume shown in the fig5.1. In the figure we can see that total volumes are 4 and unmeshed.

Fig.5.1: Volume Defined

6. tetra meshing for volume: Tetra meshing: It is also called Unstructured Mesh where the created volume filed by tetrahedral elements. Tetra rapid and tetra FEM are commonly used mesh types. In tetra rapid the Tetra Rapid algorithm meshes the Volume with Tetra Elements. In tetra FEM function automatically creates a tetrahedral mesh inside selected Volumes, initially with pyramid elements if the starting surface mesh contains quad elements. It is to be used mainly for structural applications.

Here we done with tetra FEM for better results (VOLUME MESH>Unstructured Mesh>Tetra FEM). In the fig6.1 show the tetra mesh for given model. And to conform the cut section shown in the fig6.2.

Fig.6.1: Tetra FEM

Fig.6.2: Section view

7. Check for tetcolapse: After solid mesh we need to check for tetcolapse by inputing the given tetcolapse valuve 0.2 in Quality criteria>solids.

Learning Outcome:

1. Learnt user inter face of ANSA for solid mesh.
2. Learnt CAD geometry clean up, topology, Mid-surface extraction And Defeaturing for solid components.
3. Learnt ortho tria and tria and tetra meshong for solid parts.

Conclusion

Tetra meshing is done successfully for a Rear view mirror model by eliminating geometrical errors and considering the given element quality criteria using ANSA.

(Find the attached file of Rearview mirror_volume.IGS).