Meshing the Hood of the car for durabilty test using Hypermesh

HOOD

Objective:-

To make the geometry cleanup and extract the mid surface for each component separately and mesh all the components according to the given criteria.

Procedure:-

• Given STEP file for the hood is imported and each component is checked and geometry cleanup is done on all components. All components are checked for pinholes and the duplicates, if found, and deleted.
• A mid surface for all the components is extracted using the auto extraction (offset+ planes+ sweeps). Each mid surface is renamed accordingly and kept as separate components.
• As symmetry is available at outer extract body and inner body, relative halves are kept and mesh is created only for the half regions of their mid surfaces.
• Geometry cleanup is done on the all mid surfaces and extra surfaces are created according to the requirement by using Quick edit.
• Criteria are set according to the given requirement and target element size is 5mm.
• For the mid surface (i.e. inner mid component), surfaces are divided into many parts by using quick edit options like node-line, node-node split, replacing points, toggle lines, trim intersect, project point, add points, add points on the line.
• After acquiring the good geometry file, 2D meshing panel is used to mesh the mid surface.
• From 2D meshing panel, by using auto mesh feature with mixed mesh type and keeping the flow and size in check, the mesh is done.
• Mesh is created on the divided surfaces of the inner mid separately. Mesh connectivity is continuously kept in check to keep the element connectivity.
• The good mesh is tried to achieve by varying the element density and once suitable mesh is obtained, the mesh is accepted.
• After completing the surface meshing, the auto mesh is made use for element meshing (Auto mesh with elements) regularly to obtain the best possible fine mesh.
• Elements are edited accordingly whenever required to obtain good quality mesh.
• Mesh quality is monitored regularly and required action like dragging the tria element, element optimizes, nodes optimize, splitting and combining the elements and smooth are made use to edit the mesh according to the criteria.
• Equivalence for the elements across the edges is checked and resolved.
• Rotational quads and undesirable elements are edited accordingly and some nodes are aligned as required.
• All the elements of the mesh which are done are kept at the respective components by keeping the relative surface as the current component while meshing.
• Mesh is done while keeping the surfaces in the wireframe mode for the ease of meshing.

Latch:

• Mesh is created and property of thickness 1.2mm is assigned.
• 2754 elements are created from the latch mid surface.

Hinge:

• Mesh is created only for the one component of the hinge and elements are reflected on to the other hinge component.
• Before reflecting, the duplicates are kept in the original component and elements are reflected about Y-axis by selecting a suitable base point.
• Reflected elements are organized accordingly. Property of 1.2mm thickness is assigned to both hinge elements.
• 2692 elements are created from both of the hinge components.

Outer extract:

• As symmetrical surfaces are available only half surfaces of the outer mid extract is kept and meshed for the same.
• After obtaining the good acceptable mesh, elements are reflected accordingly about the Y-axis and suitable base point is selected.
• Duplicates are made before reflecting the elements. Equivalence is checked for the original and reflected elements and equivalence is done to maintain the element connectivity.
• If possible to eliminate some of the trias and undesirable elements after reflecting the elements, the mesh is edited accordingly.
• The thickness of 0.75mm is assigned to these elements.
• 52138 elements are created from the mid surface of the outer extract.
• Surfaces which are deleted according to the symmetry are created by reflecting the surfaces and these surfaces are connected accordingly.

Inner extract:

• As symmetrical surfaces are available only half surfaces of the inner mid extract is kept and meshed for the same. Surfaces at the latch region are not symmetrical, so they are kept and elements of these surfaces are not reflected in further steps.
• After obtaining the good acceptable mesh, elements are reflected accordingly about the Y-axis and suitable base point is selected.
• Duplicates are made before reflecting the elements. Equivalence is checked for the original and reflected elements and equivalence is done to maintain the element connectivity.
• If possible to eliminate some of the trias and undesirable elements after reflecting the elements, the mesh is edited accordingly.
• The thickness of 0.75mm is assigned to these elements.
• Surfaces which are deleted according to the symmetry are created by reflecting the surfaces and these surfaces are connected accordingly.
• 39480 elements are created from this mid surface.

Result and conclusion:

• The mesh is obtained according to the given criteria, and a total of 97064 elements are created.
• No elements are missing the equivalence, so all the elements are kept with good connectivity between them.
• To capture the surface feature with the elements, some elements in the mid surface of outer extract body at the fillet regions are compromised to fail the given criteria like minimum size (1684 elements), aspect ratio i.e. AR (574 elements).
• All the remaining elements are according to given criteria.