Shell meshing the hood of a car using ANSA Preprocessor

Objective:

To extract the mid surface of the hood model and generate a mesh which follows the given criteria.

Target/ Average length	5
Minimum length	3
Maximum length	7
Aspect ratio	3
Warpage	15
Skewness	45
Jacobian	0.7
Minimum Quad angle	45
Maximum Quad angle	135
Minimum Tria angle	30
Maximum Tria angle	120
Tria Percentage	15

Case setup:

• The .STEP format file of the hood model is imported into the ANSA workspace.

• Components of the hood model are inner panel, outer panel, hinges and latch. Each component of the hood model is kept visible in separate lock views.
• Faces of the components are oriented according to the entity colour mode and a uniform colour is maintained.

• Each component is worked on separately by managing the lock views. Geometry check is done on each component and if found, errors are addressed as needed. Examples of these errors are shown below.

• After clearing the geometry check, the mid surface is extracted from the Skin option available in faces tab under topo deck.

• To bring back the parent components, undelete option is used and the faces of parent components are addressed for the connection between the faces.
• Mid surface components are organised into separate lock views. The model is checked for surface errors.
• The quality criteria and mesh parameters are keyed into the software.

• Mid surface is checked for critical areas where elements might fail for the quality. The required action like joining the adjacent surfaces, making a new cut on faces so that the elements can capture the feature without failing for the criteria.

• The perimeter numbers are placed according to the required target element length. The perimeter numbers are edited if numbers are not assigned properly. The perimeter points and hot points define the location of nodes in the mesh. These points also give the information on the fineness of the feature that is displayed.

• If the model is found to have holes, they are slide so that the edge of the holes is parallel to the nearest edge.

• Using the best mesh algorithm, a mesh is generated from the surfaces of the mid surface components. The critical areas are meshed first and the mesh generation is proceeded to keep the quality and flow of the mesh under control.
• The trias are moved, swapped and combined if needed, to align the mesh for better flow of the mesh.
• The generated mesh is reconstructed and smoothened to obtain a better quality mesh.

• Inner panel and outer panel components are big and is found to have symmetry. The symmetrical surfaces are deleted and meshed. Once the complete mesh is generated for these symmetric faces, the mesh is mirrored and made sure the connection between the elements is not lost.

• In this model, for Inner panel, since mirrored elements are not connected properly, the mesh from the initial faces is checked thoroughly and is released from the geometry. The released FE of the inner panel is mirrored and the nodes are pasted accordingly.
• All meshed components are kept in the separate visual lock.
• The mesh is checked for missing connectivity. From the Bound option, free edges of elements can be seen as red boundary and it is allowed only at single con areas.

• The thickness values are checked for each component and the model is saved.

Learning outcomes:

Mid surface extraction and shell meshing are learnt while following the criteria. Assigning the part properties and different possibilities of the model preparation for meshing is learnt. Handling the mesh flow while keeping the tria position and percentages under control is practised. Usage of different feature in the ANSA package is learnt.

Conclusion:

Successfully extracted mid surface from all the components of the model. Under many possible meshing options, a better mesh which follows the given criteria is generated.