Week 3 - 2D meshing for sheet metal

AIM

To extract the mid surface and then mesh the component with given quality parameters and assign the thickness on a hood component.

OBJECTIVE

To assign the property on each part with their parent component thickness and then mesh the component with the given target size 5mm and as per given quality parameters.

PROCEDURE

The hood component geometry file (in STP Format) is opened in the Ansa for Meshing. The hood component has four different parts which are locked differently to see each part individually to extract the middle surface and mesh the component.

Geometrical Cleanup is performed,Geometrical Checks are performed and Topological errors are fixed.Unnecessary Cons are removed.

Next,Mid Surface is exracted.

The Hood panel has five parts in which three of them have a similar thickness of 1.2mm and the remaining two-part outer and inner panel have thickness of 0.75mm. So the hood component is non-linear in its physical nature.

Extraction of the middle surface of the component can be done manually or Auto option. In this particular project,the component parts are individually extracted manually by selecting the faces and then taking the middle surface by the value of half the thickness of the parts.

The Set of commands used with selection is "Offset + Faces + Select the single face of the component + Extract".

The property is assigned in the properties panel by creating new property and giving T(Thickness) to the component as per their particular value.

After extracting the middle surface and assigning the thickness, now a component is meshed by particular process before meshing for understanding and adopting the process of meshing.

Meshing: Meshing is the finite element analysis process that divides the component at finite surface by giving the nodes and the element to solve for mathematical equations in analysis software.

The target element size is set for meshing which is 5mm. and the quality parameters values are given in the quality parameter panel. For meshing the Best option is used as suggested by experts for those like myself being new to using the ANSA ,Software to get the best practices and best possible results.

First, the hatch is meshed with given element size and to have the most fair enough fine mesh flow possible,the part is a divided in smaller rectangular sizes by using the cut option and then selecting the particular surface for meshing.

Similar steps are followed for right and left hinge. As the outer panel is the big part,it has small fillet which fails for minimum element size so that fillet then undergoes defeature by removing the cons on fillet, giving the cut on the middle of the fillet. In the inner panel, the surface is varying so to obtain the proper mesh flow the component undergoes removal of unnecessary cons and giving the proper cut to the fillet part and other surfaces.

Also, the outer and inner panel has asymmetric surface so in order to obtain mesh fast, the half of the surface is deleted and then on the remining part,the mesh is done.

While meshing, the component is observed to be failing elements for several criteria such as warpages,skewness, minimum and maximum length, max, and min quad angle. To fix them manually, the operations are obtained from the mesh panel,and the are many methods to fix them.

After giving mesh to the component the mesh flow doesn't appear to be proper, so it is reconstructed again to obtain proper mesh flow.But in order to have perfect mesh as per meshing criteria there are some rules that should be followed after meshing the component. Once we meshed the component there are some trias and quads elements. The quads are fine for mesh except rotational quads and trias for which has some rules, to be followed to fix them.

Trias management rule:

• Back to back trias.
• Opposite trias.
• Trias on edges.
• Trias on circle edges.
• Trias in three directions.
• Reduce trias.
• Trias on fillet, if possible.

Failed elements and Fixing them:

The elements which are failing for minimum and maximum length they are fixed by re-meshing it or moving them in a particular direction, this option clears the failing criteria.

Trias is fixed by splitting them and pasting at a particular area to have proper mesh flow.

The sharp edges are moved at a particular distance or reconstructed them again. The smooth options help to achieve proper mesh flow.The overlapping elements or elements which are not created properly are deleted and then recreated to have have mesh and the region is smooth again.Back to back trias are fixed by updating the option of splitting them a particular distance.

RESULTS

The mesh is finally obtained and is well formed,as smooth as possible, on each component fixing them by using several options in the mesh panel.

The elements that are failing are fixed and the quality result is obtained with less trias percentage of approx 1.53% and quad approx 98.47%.

CONCLUSION

The hood component is extracted with with mid surface and assigned to the thickness of parent component and then meshed with given quality parameters and element size with then given value and criteria fine mesh flow is achieved