Structural Meshing of the Hood using ANSA

OBJECTIVE 

       To clean up the geometry of the Hood and mesh the geometry with the element size of 5mm. The different parameters for the mesh quality are set to check the quality of the mesh.

PROCEDURE 

        Import the geometry into the ANSA and unselect the macros option and delete the extra entities.

The outer of the hood is separated using not tool and topological errors in the geometry are corrected.

                                     Geometry errors in the inner hood

The Unchecked faces and Needle faces are corrected using the auto-fix option available in ANSA and other errors are corrected using the different tools in the topo mode.

Paste - Function pastes (joins together) two or more cons segments that lie close to each other, and which usually are boundaries of different Faces. A new topological condition is created and these faces become neighboring. 

New under faces - Function defines a new surface by selecting its boundary curves and creates a corresponding face that covers the new surface. The calculated surface appears as a net.

Topo - Function automatically creates topological conditions between selected adjacent cons.

Delete - Function deletes selected faces. As the Face is deleted the neighboring topological conditions change. If the picked face to be deleted serves as a parent face to other linked faces, then extra confirmation is required for the deletion, and an option to convert all linked faces to geometry is given.

The midplane of the inner hood is formed by using the offset tool at the top layer of the inner hood and provide the offset distance as half the thickness of the inner hood. 

Offset - Function offsets selected faces by a given distance in order to create new faces. Select the offset option and choose the feature area and provide angle value as 10 and give offset value.

                                                  Midplane of the Inner hood

Rm Dbl - Function is used to identify faces that are similar in any of the four following ways: symmetrical by means of the current symmetry plane, symmetrical by a user-specified mirror plane, multiple times superimposed on the same side, multiple times repeated along a specified translation direction at given distance intervals or multiple times repeated along a specified angle at given steps. After the identification, the user can decide which faces keeping, and which ones to delete or substitute with links.

                          Green and Blue color indicates the symmetry of the Inner hood

The hood is not symmetric at the top use proj cut tool to create the symmetry plane. 

Since the part is symmetry one half is deleted and the element length of 5mm is provided and the best tool is used to create the mesh.

Best -function automatically meshes Macro Areas using all alternative meshing algorithms and keeps only the mesh of highest quality according to QCHECK. The Best function may be applied to selected unmeshed Macros, or to all visible Macros according to the chosen option. The \'Re-Generate\' option applied to selected Macro Areas where, firstly, erases existing mesh, if any, and secondly meshes them using the Best meshing algorithm. The \'Options\' configuration feature enables the user to determine the meshing algorithms to be used. The resulting shell elements are of first or second order shell elements according to the status of the 2nd Ord flag.

Symmetry

Transform --> copy --> symmetry, choose the entities & select default plane. 

                            Paste option converts single bounds to double bounds

The mid surface of the outer hood is created with the help of the Mid Surf tool and skin option is selected in it.

Mid Surf - Function turns the solid description of a thin part into a thin shell description by isolating the outer or inner skin of the solid description. The tool automatically creates the PID for the mid surface and edit the names of the PID.

                 Skin Dialog box                                             Property outer hood created

                                              Skin Geometry of the Outer hood

                                              Hemming of the outer and inner hood

Paste Inner hood with Outer hood and triple cons is created using the paste option and this triple cons are not an error. 

Release under Elements -Function releases the shell or solid elements, which have been generated on Macro Areas, from the underlying geometry or volume respectively. The node and element ID\'s remain intact. (i.e) The option separates the FEA model and geometry model.

                                                  Geometry Mesh mode

                                                 FEA Mesh mode

The surface check is used for the FEA model & values for quality criteria is provided. 

                                        Errors due to Mesh Quality Criteria

Tools used to correct quality criteria.

Reconstruct -Function is a powerful tool for the creation of a high-quality surface mesh. It examines a given mesh and performs re-meshing to correct problematic areas and optimize the overall quality of the mesh according to the mesh parameters. For Geometry Mesh all modifications are made on the underlying CAD surface.

MV Surf -Function moves a selected mesh node on the Macro Area\'s surface or a perimeter node along the perimeter segment on which it lies. Also, it moves a node belonging to the FE-model mesh on the surface which is defined by the adjacent shell elements.

The below figure shows that there are no off elements in the model.

                                                                   PID Mode 

                                                Presentation parameters dialog box

                                                         Hemming as a solid shell

 CONCLUSION

        The topology of the given geometry is cleaned and the midplane of the inner hood is formed and meshed. The quality criteria in the mesh are checked by setting the parameters and the errors are cleared.