Week 3 - 2D meshing for Sheet metal

2D meshing for sheet metel of inner Car Hood in ANSA

Aim: To mesh the given component according to the given quality criteria.

Quality criteria table

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

Image 1 Given Model

Meshing Procedure for Sheet Metal Components

Since the sheet metal components have uniform thickness and the thickness is very less when compared to other dimensions of the component and hence it is considered as 2-D Component. Therefore, to mesh these components Midsurface Meshing is done. Midsurface Meshing is the process of meshing 2-D components by meshing the mid surface generated from the component and assigned thickness to the mesh. Midsurface meshing helps in reducing the meshing time when compared with 3-D meshing for the same component. Also, it reduces the simulation time.

Meshing Procedure

1. Genration of Midsurface
2. Geometry Cleanup
3. Finding the symmetric components and deleting it half part
4. Meshing
5. Reflecting the Mesh for the Symmetric Parts.

Meshing Rules

1. The mesh should look smooth and regular.
2. Coarser mesh is to be used for the simple surface area and comparative finer mesh for the complicated surface area.
3. Back-to-back trais should be avoided.
4. Two opposite trias near each other should be avoided.
5. No mesh Transition on constant radius fillets/curvatures.
6. Tria elements at the outer edge/holes are to be avoided.
7. Avoid Tria elements connected to hole-free edge
8. Circular holes are much important in Durability, Fatigue, and NVH analysis. So it should be modeled carefully with at least one layer of quad elements around the periphery of a circular hole. Tria elements will add stiffness so it is not desired to have tria elements.

Step 1: Genration of Midsurface

First the model is checked for any geometrical errors and is cleaned using the Hot Points, Cons and Faces tools. After clearing the errors in the model the midsurface is generated using the Mid.Surface tool in the Faces Tools(Refer to the below image)

Image 1.1 Midsurface Tool

To Create the midsurface of any component

Faces>Mid.Surface>Select the component>Edit areas>Skin Offset.(Refer the below image)

Image 1.2 Inner Extract

Step 2: Geometry Cleanup

After extracting the midsurface of all the components, midsurfaces all the components are checked for any topological errors. Also some double cons are suppressed so as to get good mesh flow.

Tools used in geometry cleanup are Delete in Hot points, Release in CONS, Cut, Topo, Proj.cut, Dach in Faces.

Delete is used to delete unnecessary hot points in the cons.

Release is used to release the double or triple cons

Image 2.1 Geometry Cleanup Tools

Below image shows the images of the components before and after geometry cleanup.

1. Inner Extract

Image 2.2 Inner Extract

Step 3: Meshing the midsurfaces

Since some components are symmetric and hence half of that component is deleted and the remaining half is meshed and reflected. Below images shows the images of the Symmetric components.

Image 3.1 Inner exract

To mesh the components the tab is changed from topo mode to meshing mode by clicking the meshing mode icon. In the Meshing tab, Best Mesh tool is used to mesh the components. And to get the better mesh is the Best mesh didn't give good mesh Improve mesh, Reconstruct Tools are used to get good mesh.

Image 3.2 Meshing Tool

Image 3.3 Reconstruct and Improve mesh tool

Before meshing the component the quality criteria is uploaded. Below image shows the image show the quality criteria uploaded before meshing.

mage 3.4 Quality Criteria

After adding the quality criteria, the mesh parameters are to be added. Below image show the image of the mesh parameters.

Step 4: Reflecting the mesh

Transform option is used to mirror the half meshed component.

To reflect the mesh Transform>Copy>Select the components>Symmetry>Mirror 3 points plane> Select 3 points on the edge of the half mesh>Apply>Finish.

Image 4.1 Inner Extract

Result:

For the given model, the midsurface for all the component is generated and checked for geometrical error and mesh is done on the midsurface with the given quality criteria.

https://drive.google.com/file/d/1959LnsP_69wa25n8c9E8-x55FgtDu0Zt/view?usp=sharing