Hypermesh Week 7 Challenge - Manual Midsurfacing & Meshing of Car Backdoor

OBJECTIVE

To mesh the given backdoor geometry of a car through manual midsurfacing process and the RADIOSS solver, as enunciated in the week 7 videos. To also ensure that mesh is of highest quality with low number of trias and good mesh flow.

CAD MODEL IMAGE

The model comprising of all its components:



It is comprised mainly of the following components:

PROCEDURE

1. The part needs to be meshed component by component so we need to pick one of them and extract its midsurface. We will need to carry out this manually. Firstly, a new component is created and we'll name it 'MS of X': X being the component that we will be working on.

2. After that, we can go to the component to be midsurfaced and measure its thickness. Which is 0.75 mm in this case. We need this for manual creation of midsurface. And this is done using the offset tool under surface edit.

3. The offset tool requires a measurement half of the thickness. Which would be 0.375 mm in this case. We can select any one face from any one of the faces. And then, right click surfaces and select 'by face'. When this is done, the entire face is selected. Not the entire component.

4. Before carrying out this step, we need to ensure that the newly created midsurface component is our current component. After confirming, we can select 'duplicate' by selecting surfaces again. And now, we can select 'current component'. The offset of the component is now transferred to our newly created component. But we are yet to offset the face.

5. Before selecting the offset button, we can verify the upcoming offset's normal, which could be in the opposite direction. If so, we can use the 'reverse normal' option to reorient it to the opposite direction. And then we can click offset. We now have our midsurface generated onto the newly created component.

6. Considering the size of these components, to facilitate the meshing process, we can work on half of the component and reflect it later as they are symmetrical about the centre. This can be done by using the delete option and selecting half the component. If required, we might need to use the split surface option from the quick edit section.

7. i. As is customary with meshing, we should start meshing from a certain region and work our way from that region (preferably one with more free edges). To help with this, we can make use of cut lines (quick edit > split surface node) to split the surface into smaller surfaces for better mesh control.

ii. Additionally, we need to toggle lines that would hinder mesh flow and use our best judgement to make sure that the surfaces we create do not encourage tria formation (like pointed edges).

iii. After mesh is created, we can clean the mesh using various tools. Primarily, we will be using the element optimize tool, the drag tria tool and to an extent, the swap edge tool. These are accessed from the quality index section in the 2D menu.

iv. After we take care of each surface (meshing and cleaning up), we can move onto the next. The process is repeated until we mesh the entire component.

8. Since the component is halved, we will need to make use of the reflect tool to create the other symmetrical half. Reflect tool can be accessed by going to the tools menu. We will need to select the elements to reflect first. Do take care not to select regions that are not otherwise part of the other half, since both halves may not be completely symmetrical. And then we can select the axis on which we are reflecting and then the base point. After that, we need to right click 'elements' in the reflect toolbar and select duplicate. And then we can click reflect. This will create the mirrored half of the current component.

9. We will now check for equivalency by going to the edges section in the tools menu and previewing equivalance for varying tolerances (ranging between 0.2 mm to 2 mm). This is to ensure there are no misaligned elements or free edges, which we can also check using a different option in the same section. The preview equivalence option shows us the nodes that require equivalencing. They are rectified by clicking the 'equivalence' option in the menu. If some nodes haven't been tended to, it may require manual fixing, using the replace node option (F3).

10. After equivalencing, we can check for duplicates through the check elements tool in the same menu. If duplicates exist, we can click 'save failed', move on to the tool menu, select the 'delete' tool, select elements, right click element and select retrieve and then click the delete button. This should handle the duplicates.

11. Finally, we can assign a thickness for each of our midsurfaces. They all measure the same - 0.75 mm. We can do this by right clicking and creating a component in the component tree. After a property is created, we can go to its section in the bottom left and scroll down to assign the aforementioned thickness. Then we can assign the thickness by selecting the midsurface, going to its properties box on the bottom left and assigning a prop_id, by selecting the thickness property. Similarly, we can assign the material as well through the same process.

FINAL MODEL IMAGES (MESHED)

RESULTS

The geometry has been manually midusrfaced and meshed with the best quality and mesh flow possible using RADIOSS. The mesh was assigned the appropriate thickness (0.75 mm). Components that did not contribute to the final mesh have been removed from the file as well.