Week- 8 - Solid meshing

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

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

Importing cad model

A rear-view mirror (or rearview mirror) is a flat mirror in automobiles and other vehicles, designed to allow the driver to see rearward through the vehicle's rear window (rear windshield).

In cars, the rear-view mirror is usually affixed to the top of the windshield on a double-swivel mount allowing it to be adjusted to suit the height and viewing angle of any driver and to swing harmlessly out of the way if impacted by a vehicle occupant in a collision.

The rear-view mirror is augmented by one or more side-view mirrors, which serve as the only rear-vision mirrors on trucks, motorcycles and bicycles.

Import Rear view mirror.IGS in to the ANSA: Import the given Rearview mirror.IGS in to the ANSA

After Topo all the surfaces are connected.

Setting the optimum length. This prepares the model for meshing.

Setting the quality criteria unlike sheet metal meshing here we are not going to check jacobian, taper, minimum and maximum quad and tria angle. Only min,max length is given for quality criteria.

Geometry check:

If the component greater tham 6mm or can not be measured ( Hollow) considered as solid geometry. For solid geometry we will not extract midsurface. Surface mesh is done later it is converted to volume mesh.

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. 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. shows the fixed all Geometrical errors.

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, triple con etc. those errors are shown in fig.

After geometery check

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.

Here ortho tria must be selected but while doing mesh one 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 for meshing 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 must be satisfied.

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 fig In the figure we can see that total volumes are 4 and unmeshed.

Tetra Rapid: Very fast and robust tetra mesh generation for any model. Recommended for all cases.

Tetra FEM: Old tetra mesh generation for smaller models with thin volumes. Significantly slower than Tetra Rapid, it should only be used if Tetra Rapid does not perform well in a specific case.

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.

6. 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:

• Learnt user inter face of ANSA for solid mesh.
• Learnt CAD geometry clean up, topology, and surface for defeaturing for solid components.
• Learnt ortho tria and tria and tetra meshing 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