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

Hood component is given with five different parts:

• Hatch.
• Left and right Hinge.
• Inner panel.
• Outer panel.

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

S.No	Quality Criteria	Value
1	Target/Average length	5
2	Minimum Length	2
3	Maximum Length	7
4	Aspect	3
5	Warpage	15
6	Skewness	45
7	Jacobian	0.7
8	Minimum Quad Angle	45
9	Maximum Quad Angle	135
10	Minimum Tria Angle	30
11	Maximum Tria Angle	120
10	Tria Percentage	15

PROCEDURE

The hood component geometry is open in the Ansa for Meshing, the file is open with STP format, 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.

command: [ Inot + Neighb (All) + Selecting all faces + create store lock (For all components)].

For Topology checking the unnecessary cons in parent component the deform faces, cracks in the geometry. After checking the errors in checks that can be fixed auto but executing the autofix option after fix the error.

command: [Checks + Geometry + except single cons check all other entities + execute + Auto fix].

Middle surface: The middle surface is the middle part of the parent component which has two surfaces by measuring the thickness of the component, selecting a single face, and extract at the mid-value of the component.

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

To extract the middle surface of the component can be done manually or Auto option. The Right hinge, Left hinge, and Hatch extracted manually by selecting the faces and then taking the middle surface by the value of 0.6mm.

Command: [Offset + Faces + Select the single face of the component + Extract].

And the Outer and inner panel is middle surface extracted in auto option by selecting the entity and then giving he middle value of component 0.375mm

Command: [Mid surface + skin+ select component + Checking the green, red and blue on the surface + Extract mid surface]

Extracting the mid surface of each part, the component is assigned to the property with their individual thickness as the three parts have a similar thickness so they are assigned to the 1.2 mm value and inner panel and outer panel at 0.75mm value.

The property is assigned in the properties panel by creating new property and giving T 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 to understand the meshing and process to adapt it.

Meshing: It 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.

To adapt mesh the component changed to the length of the target element size of meshing which 5mm. and the quality parameters value is given in the quality parameter panel. For meshing the Best option is used as new to the ANSA, to get best practices as a new start.

First, the hatch is meshed with given element size, to have the fines mesh flow the part is a divide in smaller rectangular size by giving 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 is has small fillet which fails for minimum element size so that fillet is a 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 removed with unnecessary cons and giving the proper cut to the fillet part and other surfaces.

Also, the outer and inner panel has asymmetric surface so obtain mesh fast, the half surface is deleted and the mesh is done.

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

After giving mesh to the component the mesh flow doesn't get proper, so it is reconstructed again to obtain proper mesh flow but 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 has some rules, so that need to be followed.

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 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.

RESULTS

The mesh is obtained significantly on each component fixing them by using several options in the mesh panel. as the symmetric surfaces are deleted and meshed on single surfaces but the as a result on the outer panel the mesh is not connected as it used with auto paste option but it not working as well.

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