Project

Midsurfacing & Meshing of Car Backdoor Challenge

AAadity K. Singh20 Feb 2021

AIM:- To extract the mid surface and generate the mesh on the Car Backdoor model in Hypermesh

Procedure:-

Step 1- Importing and Geometry Cleanup

- Import the Model .igs file as geometry.

- Visualize the model if it has any deformities in its surface or free edges, which can be visualized in wireframe mode & By Topo mode.

- After importing, change the Geometry color mode to By Topo, if the model consists of solids, which is not required for our further process we will delete it.

- So we delete the solid from the model, which also benefits in less time consumption for computing in Hypermesh.

- Then, we check the thickness of all the components.

- To check the thickness of the component, we go to the distance option in Geom (F4) and select the two points option, then we select any two points from the component and find the thickness of the components.

- Thickness = 0.75mm

- Here, we are checking the thickness of the model, so as it is required to extract the mid-surface manually

Step 2- Extracting Mid-Surface

- We extract the mid-surface manually, for that we go to the offset option in the surface edit option in the Geom tab

- Manual mid-surface is a complex method but it is very useful in extracting the mid-surface for the complex geometry.

- For manual mid-surface in offset option in surface edit option, first, we select the surface to be offset, duplicate it, check for the normal where it is to be offsetting give the distance than offest it.

- We need to do this process for every surface one by one, as the thickness of surfaces might be different.

Note- For multiple surface selection, it should be mandatory that the normal should be unidirectional.

- As all the three parts are symmetrical in geometry, we manually extract the mid surface for half of the part, and can reflect it to create the complete part

- From tools Reflect can be done by duplicating the current surface and reflect the particular axis and 1-base point.

- Mid surface is extracted for all the components.

Inner Panel Mid-surface

Outer Panel-1 Mid-surface

Outer Panel-2 Mid-surface

- After extracting the mid-surface for all the components of the backdoor, we need to rearrange/toggle the construction lines and delete the unusual points so that to get a good mesh flow.

- At the place of fillets and curves, we need to properly rearrange the construction lines, so as the meshing will follow the original geometry of the model.

- We should also delete/toggle the construction lines that are too close and can cause minimum element length failure.

- We also create the washer split at the holes, so can obtain a proper mesh flow.

Step 4- Generate Mesh & Optimize the Mesh quality

- After extracting the mid-surface and do all the processes required for the proper mesh, We need to provide all the required criteria for the meshing.

- The meshing will automatically generate according to the criteria provided.

- All panels are symmetrical therefore, after extracting mid-surface meshing is done on one half of the mid-surface and then reflecting the other half.

- Now, the automesh is done, keeping the element size to be 5 and mesh type-mixed in auto mesh option.

- After meshing, there are so many back-to-back trias and quad elements that will be formed, So, we need to improve the quality of the element by removing or minimizing trias and quad elements.

- To optimize the element quality, we can use tools as element optimize, drag tria, smooth, edit-element (split/combine/create).

- To optimize the elements we can use the Rebuild option and also remesh the element of a particular place.

- This will remove all the element failure from the mesh, as it is necessary to have a proper mesh for the analysis, if our mesh flow or mesh element is not properly made, we cannot calculate the accurate analysis.

- After meshing one half of the model, the elements of the half part are selected and it can be reflected using reflect option in the tool option.

- After reflecting the elements to the other half, it might get the free edges which we need to check and remove

- For that we will go to edges in tools select the displayed element of a particular component and click on find edges, it will show the free edges if it is unnecessary free edges are there, we can fix it using the equivalence option.