2D meshing for sheet metal

 2D meshing for sheet metal

AIM:

1. Take the sheet metal cad model.

2. Capture the mid surface .

3. After that mesh that mid surface and assign quality criteria .

4. Then assign thickness to that mid surface .

Procedure:

1. Geometry Load

2. Cons resolution 

3. Check surface connectivity / Topo

4. Geometry check

5. Mid Surface generate

6. Giving quality criteria and checking the geometry as per quality

7. Meshing 

8. Assign thickness to Mid Surface

 

1. Geometry Load :

First we are Loading the geometry in Ansa

2. Cons resolution :

We have to increase the resolution of cons so that the curves, fillets and other portion of the geometry can be shown properly, so go to mesh - perimeter - length - 1 mm

3. Check surface connectivity / Topo :

To check surface connectivity go to Topo module - Faces - Topo

4. Geometry check :

so go to check manager - geometry check and Fix all geometrical errors.

5. Mid Surface Generate :

We are generating the mid surface as length of the geometry is very large as compared to thickness so we can neglect the thickness and we are willing to generate 2d mesh as it can produce less number of elements than 3d leading to less number of errors and quality faliure so that require less computational power .

We can generate mid surface by Topo -Faces - mid surface - skin option

select whole geometry and middle click . Before selecting in the options list select - delete original faces - No and skin property - Ask always 

select the upper green surface and middle click , then select the offset value and again middle click , then in PID poop up select on the PID other than main geometry - right click - edit - rename it - ok and double click on it .

6. Giving quality criteria and checking the geometry as per quality:

Before giving quality criteria we have to orient the surfaces by Topo - Faces - orient 

Then apply and ok .

Set target length as 8mm 

Before meshing we have to fix some errors in geometry that may lead to quality faliure ------

a. Hot points nearer less than minimum length(3mm)-

b. Feature lines nearer to each other :

c. Construction line when there is no change in geometry :

We have to remove the lines in mesh module by macros - join and delete hot points by Hot points - Delete option.

 

7. Meshing :

Now we are going to mesh the model one by one macros by mesh - mesh generation - Best mesh 

To remove the errors go to shell Mesh - reconstruct - select the macro and middle click

 

WE can remove the quality faliures by reconstruct - reshape - smooth and Fix quality options .

In this way we can mesh all the macroes in the geometry and we can slide the trias by Split(Forward movement) , Swap(Left/Right movement) and Paste(Backward movement ) one by one from the edges and fillets so that the trias should not create any error . 

We can Join two macros by join option in macros and transform the mesh edges by edge2perim . 

In this way we can mesh all the macros and remove the off elements by reconstruct / reshape / smooth option . 

Now we have meshed the whole surface , we have no off element , total 4215 elements , quads - 3841 , trias - 374 .

8. Assign thickness to Mid Surface

Open quality criteria - presentation parameters - check Draw shell as solid - Apply and Ok

 

Conclusion :

In this project we have learned that - 

1. To create mesh on the surface where surface length is very greater than its thickness we are creating a mid surafce as it helps us creating 2D mesh as the 2D mesh is more convenient than 3D in terms of no of elements are less , less off elements so required computational power is also less.

2. We are avoiding trias nearer to the edges and fillets as trias have more stiffness(Force per unit length) as compared to quads so for more stressed element if it exist near the edge it can lead to break / faliure of the edge . 

3. We can not remove all the trias near the edges as for quality criteria .

4. We may need to delete some hot points to make the trias into quad and increase number of edges by peremeter -  Num+-  to keep the quality criteria constant.

5. For crash test uniform mesh is preffered (i.e. some trias may exist) but for structural analysis no trias should exist .