Week 5

AIM:

In order to perform a Structural Analysis with the given CAD Geometry (Rear View Mirror – Solid Part) by using ANSA. The process involved as follows

• Importing CAD Geometry into ANSA
• Topology Operation
• Performing Geometry Cleanup
• Applying given Quality Criteria - Presentation Parameters and Meshing Parameters
• Mesh Generation
• QC and Mesh cleanup
• Solid Meshing (Tetra Mesh)
• Check the model for Tetcolapse issues.

PROCEDURE:

• Import the CAD Geometry into ANSA

So, here we have a Rear View Mirror which is a Solid 3D Part (hollow inside). Since it is cross-sectional – Thickness can’t be measured.

TOPOLOGY OPERATION

The Topology is used to recover the results of (Hot Points – Release) and (CONS – Release) functions. It is also used to recover the Topological conditions of a Face that was undeleted by the (Faces – Undelete) function.

Before doing Topo, Let us refine the Geometry with perimeters length. To do so, Go to MESH - Modules > Perimeters > Length. Now Length perimeter pop-up appears. Window select the whole Geometry and middle mouse click to set perimeters length of 1mm. Do the same for the Macros. Now we can see that the model is refined.

Also do an Orient Visible under Faces. This function sets a uniform orientation direction to all visible Faces. This results in a good mesh flow.

Now do a Topo for the Geometry by Modules > Faces > Topo. Window select the whole model and Middle mouse click will do the operation.

GEOMETRY CLEANUP

Geometry cleanup is done in order to get a better Mesh flow. To do so, Go to Checks Manager > Geometry. Checks Manager popup appears. Hit on Execute.

Here, we can see on the Geometry check pop-up that ANSA is showing some errors on the CAD Geometry. The errors are Triple CONS and Needle Faces. Since it’s a Solid Part we perform a manual fix to avoid further issues. Select all the Triple CONS errors and hit show only. Now ANSA shows only the area where we have Triple CONS formation. Go to > Neighb > 1^st Level which will bring the neighbor area visible.

In order to clear the error. Release the Triple CONS by CONS > Release in Modules.

Now hide the surfaces associated with the Triple CONS with NOT command. After which you will find two Needle faces which tend to from Triple CONS. Other areas where ANSA pasted two different surfaces which lead to Triple CONS formation. Then bring back the hidden faces with Neighb > All and do a TOPO.

Again do a Geometry check, where ANSA shows no error. Hence the Geometry is clean for Meshing.

Surface Cleanup

Remove unwanted hot points and Construction lines throughout the Surface. And Divide the surface by creating construction lines. To do so Go to Modules > Cut which will lead us to a Good MESH flow.

Rename PID with respective Part Name

We have 4 Solid parts in the Rear View Mirror. So we have to Name each of it in the PID. As shown in the below Fig.

Now, The Geometry is ready for Meshing.

MESH GENERATION AND QUALITY

To start with the MESHING process we have to set the given Quality Criteria in SOLIDS since it is a Solid 3D Part.

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

To do so, Press F11 in the Keyboard. A Quality Criteria - Presentation Parameter Pop-up appears. Set the above given values.

In the Presentation Parameters - Enable Elements % and and slide the Detail on demand effect slider to the (all details). Then hit APPLY then OK.

Next Open the MESH PARAMETERS in Utilities TAB. Then feed in the (Basic)

Mesh - GENERAL

Ortho Tria (Type)

Order of Mesh – 1^ST ORDER

Then we have to add our Target length of the mesh flow as 1mm. And set the Min. Target Length as 0.5mm and Max Target Length as 2mm. Then hit ok.

Now, we start with the Meshing process.

Go to MESH - Mesh Generation > Spot Mesh

The Spot Mesh algorithm gives better results than the free meshing method and creates the optimum number of shell elements, taking into account the element type already selected and the defined meshing parameters.

There are four parts in the Geometry.

• Swivel Mount
• Swivel Joint
• Mirror Holder
• Convex Lens

So we have to Mesh each part Individually. Keep in Shadow mode in Drawing Styles and start meshing. First we Mesh the curved surfaces and fillets with Mesh Generation > Spot Mesh (Mesh type Ortho Tria). After meshing the areas check the mesh for any Kinks and Dips. Reconstruct the area if any present. To do so Shell Mesh > Reconstruct will do the work. And also check for quality issues in Hidden mode (Drawing styles) simultaneously. Then on flat surfaces we change the Mesh type to (Tria) at Spot Mesh. Right click on unmeshed area shown in the user interface (work area) and click show only. Then window select the unmeshed areas and middle mouse click. Now Tria Mesh deployed on the Flat surfaces. Simultaneously do the same for all the parts.

The Kinks formed in the Convex mirror part during Mesh is shown in the below Fig.

Do a Reconstruct in Shell Mesh (Mesh Module) will solve the Kinks issues on the surface. The solved issue shown in the below Fig.

Now, we have completed with Meshing. The complete part is shown in below Figs.

SOLID MESHING

Solid Meshing is nothing but a Volume added with in the hollow space of a 3D Solid Part with Unstructured (Tetra Mesh). The Mesh is created based on the active Mesh which we performed before in Mesh generation. This is a whole new experience. And also a new skill I learnt.

There are two types of Solid Mesh.

• Tetra Mesh (Unstructured Mesh)
• Hexa Mesh (Structured Mesh)

In this challenge we are using TETRA MESH (Unstructured Mesh) for Solid Meshing.

Before that we have to Define the volume. This function defines new Volume entities. To do so, Go to V.Mesh Module > Volumes > Define > Manual. A pop up appears and we have two options AUTO & MANUAL. Select MANUAL. Window select the FE Model Mesh or Meshed Macros. And middle mouse click. A PROPERTY HELP dialogue box appears. Here, Go to New > PSOLID. PSOLID dialogue box appears. Name the Psolid. The values are same. If provided we must change the PID & MID value. And hit OK. Now we have defined a PSOLID ID. Double click on it to Define as New Volume Entities. So now we can see that the FE Model Mesh is defined as a New Volume Entity. The FE Model Mesh will be highlighted. This process is shown in the below Figs.

Now we have to Mesh the Volume. To do so In V.Mesh > Volumes > List. A Volume popup appears. Select ID (We can see that the defined FE Model Mesh is highlighted) and Right mouse click. Then click on REMESH. A Volume Type popup appears. Mark the volume type as Tetra Rapid and Hit OK. The Volume is Meshed. REMESH - This command will mesh the Volume with the same Algorithm and the same Parameters that have been used the last time. The process is shown in the below Fig.

Similarly we have to define each FE Model Mesh individually and Mesh the Volume. The complete one is shown in the below Fig.

Now the Solid Meshing is done.

Quality of FE MESH

Qulity of Solid Mesh

Tetra Mesh (Unstructured Mesh) Cross Sectional View.

CONCLUSION

• Topology is Done
• Geometry Cleanup is done by fixture of Triple CONS and Needle Faces.
• PERIMETERS and MACROS are set to 1mm.
• Surface cleanup done for better MESH flow.
• Given Quality Criteria - Presentation Parameters and Meshing Parameters applied
• Mesh generated using Mesh Type - Ortho Trias in Curved Surfaces and Fillets and Trias on Flat Surfaces.
• Checked the model for Quality Criteria and Quality issues (Kinks) were solved.
• Volume Defined and Solid Meshing is done using Tetra Mesh.