Hypermesh - Project 1 - Meshing of Car Door Panel

OBJECTIVE

To generate the midsurface, clean up and mesh the given plastic component of a car door's plastic panel keeping in mind the given quality criteria.


MESH QUALITY CRITERIA

Target Element Length = 4mm

CAD MODEL IMAGE




The component is the inner portion of a car door which is usually made of plastic.

PROCEDURE

1. After the model is imported, the component needs to be separated into multiple sub-components considering the intricacies and complexity of the component. Different regions have different thicknesses so it's a good idea to segregate based on thickness.

2. Certain regions like those shown in the picture can be ignored and won't be meshed.

Furthermore, some ribs have thicknesses in excess of 5mm. Such ribs won't be midsurfaced and meshed.


3. Before proceeding, the component needs to be defeatured of its fillets. This can be done by accessing Geometry > Defeature > Surface Fillets. All the surfaces need to be selected for the algorithm to detect the fillets within the radius thresholds specified. The next menu lets you remove the detected fillets.

4. Moving on to segregation, we need to assign each region to a separate collector using the Tool > Organize function. As seen here. [PIC] Each of the regions is copied/moved onto a new collector. Before moving, a new collector needs to be created to house the region that is to be organized. This can be done in the component tree by right-clicking and by accessing Create > Component.

The destination component would be the new collector that was just created.

4. After assigning and separating them into collectors, we can go ahead and extract the midsurface on them one by one. There are two ways to extract the midsurface. We could use the automidsurface option through Geometry > Midsurface but this may not be ideal in most situations here. Instead, we can use the offset option in Geometry > Surface Edit > Offset. The thickness is measured and in each case (using the distance function by pressing F4 or by accessing it through Geometry > Distance), one face of the component is offset to half the thickness through the centre of the cross-section of the region/sub-component.

The direction of offset can be checked using the vector normal option. It needs to be reversed if the offset direction is in the opposite direction.

This offset procedure is carried out for all the components that are to be meshed (with reference to #2).

5. After generating the midsurfaces, we need to attach them to each other as in every case, the generated offsets would be hovering. To do this, we can extend the edges that need to be attached to the corresponding surfaces using Geometry > Surface Edit > Extend.


The edge to be extended needs to be selected and then the target surface(s). For example:




In other cases, there will be excess surfaces at intersected regions. They can be deleted Geometry > Surface Edit > Trim with Surfaces/Planes and selecting the 'Self Intersecting Surfaces'. They can then be deleted manually using the delete option.

6. After the midsurfaces are generated, we need to carry out cleanup of the midsurfaces to ensure the minimum length is achieved for all elements of the mesh. Also important to prevent the formation of trias wherever possible by manipulating surface features to facilitate good quality mesh.
This is done by using various quick edit tools like the toggle, replace and split-surface node options. These tools can be accessed via Geometry > Quick Edit. 

7. Before we can begin meshing, we need to input the required mesh quality criteria through Preferences > Criteria File Settings. The mesh quality criteria is entered here.

8. After that, we can go ahead and mesh each sub-component one by one, ensuring meshes between connecting surfaces are equivalenced properly. The target element length is 4mm. We can input this in the mesh options at 2D > Automesh. Select the surfaces that are intended to be meshed and click 'mesh'.

9. After meshing, care is taken to get rid of opposite trias, trias touching feature lines and rotational quads.

The tools to fix this can be found in the quality index section under 2D. We can make use of the drag tria tool wherever possible to move trias and combine opposing ones to get rid of them. Furthermore, remeshing using the same automesh tool as discussed in the previous step can help fix mesh issues.

After dragging a tria, it's suggested to use the smooth tool in 2D > Smooth to ensure best possible mesh flow. The elements need to be selected and the flow is made better according to the number of iterations of the tool, which can be adjusted in the same menu.

10. After ensuring that we have the best possible quality mesh, we can go ahead and assign the thickness for each meshed component. To do this, we need to go to the collector section and right click to get the option to create a property. We can go ahead and name them 'Thickness x' with 'x' denoting the amount of thickness. Multiple thickness properties need to be created as we have seen how many different thicknesses are present within this model among different sub-components.

To edit the property, all we need to do is select the thickness property. There should be its entity editor box on the bottom left. We just need to go to the option that says 'Thick' and assign the value there (In the image, since the property is for a thickness of 3.6mm, we have assigned the value as 3.6).

11. After creating the property, all we need to do is assign the thickness property. This is done by right-clicking the respective component and clicking 'Assign'.



We can then select the right thickness and click apply. The same process is carried out for each component, with respective thickness properties created and values assigned accordingly.

12. To finish up, we can ensure that there are no free edges. This is done by accessing the edges section through Tools > Edges. After selecting all elements, we can click 'find edges' for Hypermesh to generate a new component that highlights all the free edges using an outline (by default, in red).

If there are free edges, we can use the equivalence tool in the same section to connect the elements causing the free edges. The preview equivalence option finds such regions within the search radius (tolerance) of a node that is not connected to another nearby. The 'equivalence' does the obvious by connecting them.

Finally, we can check to see if there are any duplicate elements through the Tools > Check Elements and selecting 'duplicates', with all meshed components on display. If duplicates are present, they can be 'saved' by clicking the 'save failed' option. Then we can go to the mask option and 'retrieve' the duplicate elements, mask them and then mask reverse to mask all the other elements. Now, with just the duplicates visible, we can go ahead and simply delete them.

13. Finally, we can view the mesh with thickness using the '2D Detailed Element Representation 'tool as shown here.

FINAL MODEL IMAGES

RESULT

The given side door panel was meshed as per given quality criteria. Due to it being a plastic component, different regions having different thicknesses was prevalent and the component was split into multiple sub-component as a result before meshing and they were assigned their respective thicknesses.