Meshing a Back Door Component of a Hatchback Car

Objective:

To extract a proper midsurface using automatic methods and manual offset and also to mesh the given back door model respecting all the aforementioned quality criteria.

Procedure:

Step 1. Import the given IGS model file, delete the solids and then extract the midsurfaces for each component individually.

Step 2. The midsurface is extracted using the automatic "offset+plane+sweep" method. At crucial and complex places (like in the picture below) where the extracted midsurface was not proper were replaced using manually offseting the model surface to the midpoint of the thickness. And then the offset surface was stiched with the already extracted midsurface using replace points and surface edit and trim tools.

Step 3. The topology repair or cleanup is performed using "autocleanup" option and again manually to suppress/unsuppress edges in the midsurface to maintain continuity and to add washer splits near holes.

Step 4. The given element meshing criteria is fed into the quality criteria parameters.

Step 5. The symmetry in the geometry (for all the three parts) were studied in prior to meshing and the symmetrical halves were meshed and reflected according to the geometry.

In case of Back Door Inner Panel, the geometry was partially symmetrical and those regions were meshed and reflected.

Then, the asymmetric regions were meshed. These regions were marked below in the picture.

To attach or merge these newly created element for ensuring continuity and equivalence in the reflected region of the mesh, the already reflected mesh element nodes that borders the assymmetric surface regions were associated with the respective surface edges and the meshing operation was performed.

Again the discrepancies between the elements were sorted out using the replace node options.

Step 5. The midsurfaces are meshed individually. The element densities are again modified to fit the curvature in the geometry. The free edges are then deleted.

Step 6. The failed elements are found under the quality index section. The failed elements are extracted alone by masking the rest of the elements. And the adjacent elements of the failed ones were unmasked and meshed again to achieve zero failure. The failed elements were also corrected using the "cleanup tools" options like Place Node, Node and Element Optimize, Combine and Drag Tria Elements and others. Opposite tria elements and rotating quads are undesirable for the stress-strain analyses, so they were reduced by implying the above techniques.

Step 7. The remeshed elements were smoothened to achieve an uniformaity in the mesh flow pattern. The process is repeated until the mesh is successful with no discrepancy and the required meshing criteria are met.

Step 8. The elements are tested for equivalence, dependency, penetration and normal vectors checks and zero failure is ensured. The shrink element option is used to check the over lapping of remeshed elements and were cleared.

Step 9. The material and properties were created and assigned to the part components. Material assigned is steel and the properties assigned were element card image as shell and thickness of 0.75,as measured from the given components.

Result:

The elements were meshed to meet the specified meshing requirement criteria and no element failure is ensured, also respecting and adhering to the best practices.

The elements in the hemming region of the upper and lower body components were expected to failed, as we try to capture the geometry and defeaturing the surface to eliminate the curvature will not follow the geometry of the component as this is an essential feature and not an aesthetic profiling or feature with no real purpose.

Also, a few elements failed in the surface regions with dimensions less than the allowed minimum element length of 4. Those regions are marked in the following snapshots.

The consolidated list of meshed element quality indices for all the three components is shown in the below image.

The # of trias for the entire meshing was 1.4%, well less and within the designated limit of 15%