Meshing of Car Hood (BIW Component)

Aim- To mesh the given BIW car hood component.

Step1- Geometry check was done for the entire model. Several issues such Triple Cons errors, needle faces, cracked faces was found. Some of these had to be fixed manually , while others could be auto fixed by ANSA.

In order to manually remove unwanted triple cons, first release the triple cons by selecting them and clicking CONS->RELEASE. The triple cons get fragmented into separate single cons. Now look for the appropriate surfaces and stitch the single cons together by using the TOPO option. The single cons are stitched together to form double cons. This is repeated for the entire component, till there are no triple cons issues. Needle faces are when the cons are not stitched together properly,causing the faces to be sort of pointed. The cons can be released manually and stitched together ,while deleting the unecessary cons. The issue can also be fixed automatically by ANSA, by right clicking on the error, and selecting FIX.

Example of Needle Face

Step2-The next step is the mid surface extraction. We extract the mid surface so that we can easily perform the pre processing and the meshing without affecting the parent geometry.It is essentially the surface which represents the shape and structure of the component, on which we can make changes and perform meshing, for analysis later on. There are several methods to extract mid surface, here two different methods are used.

On keen observation, we can observe that the given hood consists of 2 main parts or regions- the inner hood, and the outer hood. The inner hood contains all the main details and features, while the outer hood is the cover (seen outside the car). Using the commands of AND,NOT,INOT we extract these two parts separately and store them as different lock views.

Inner Hood-

Outer Hood-

Now , we extract the mid surface of these 2 parts separately. For the inner hood, manual mid surface extraction is done, by using the OFFSET command. The OFFSET command is selected, and then we choose FEATURE selection with an angle of 40 degrees. On clicking, the entire face of the hood gets selected. Enter the offset distance as half the thickness value (measured earlier) and click ok. The mid surface for this part is extracted as shown.

For the outer hood, we use the auto mid , or MIDSURF option. The faces are selected after clikcing this option , thickness is entered and the mid surface is autmatically generated.

After extracting the mid surface, a unique PID is assigned to each mid surface and then stored. This helps to view and edit it easily , later on.

Step3- The next step in the process is the actual meshing. Before meshing, we have to set the mesh and quality parameters required to be met. They are entered according to the given parameters.

After this, we can proceed with the meshing. We divide the component into different areas using the CUT option. The existing CONS can be removed and modified where needed. This does not affect the parent geometry as we are doing this on the mid surface. Some of CONS might be arranged in a haphazard manner, as they are slanted. These can be removed and replaced with straight CONS , to generate a uniform mesh in that area.

This process is repeated to remove all the OFF elements and create an error free mesh.

Mesh flow refers to the appearance and uniformity of the mesh. To get a uniform mesh flow we have to reduce the tria elements as much as possible. After creating a mesh this can be done using the RECONSTRUCT option. Manual mesh improvement can be done using options such as SPLIT,SWAP,JOIN and then SMOOTH operations.

Conclusion-

The given component was meshed according to given quality criteria.

Link for the part-

https://drive.google.com/file/d/1VlddTJLrNm3V3T90EtVi3HjQctVh_yyN/view?usp=sharing