Week 3 - 2D meshing for sheet metal

HOOD MODEL [ANSA]

 

AIM:

For the given Hood model,

1. Take the mid surface for all the components after checking the geometrical errors.
2. Mesh the mid surface with the given element Quality criteria.

SI 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	.7
8	Minimum Quad Angle	45
9	Maximum Quad Angle	145
10	Minimum Tria Angle	30
11	Maximum Trai Angle	120
12	Trai Percentage	15

[ In the hemming region (in the Outer panel’s bend region), Elements will fail for the Min length error due to the very small surface to capture the curved surface. In order to solve this Min length error, go for ‘defeaturing’ the midsurface.]

 

PROCEDURES:

In TOPO Module

• Geometry check
• Check for Geometry errors from Tool Menu Bar.
• Execute the operation and wait for the results.
• If Errors are generated then select all the Errors. Right click the mouse button to auto fix the errors.
• If not cleared, fix manually by releasing the cons and applying TOPO from TOPO Module.

2) Lock the VIEWS.

• Lock the views by selecting each component separately for generating Mid-Surface.

3) Mid surface creation.  

• Mid Surface creation is done by choosing Mid surface Option from Faces Option in TOPO Module by switching OFF deleting the Parent Geometry.
• Once the Mid surface is created, separate the mid surface from the parent Geometry using Or/Not/I-Not from FOCUS tab. 

4) Save each Mid surface views in LOCK views for each component.

5) Orient the surface by which grey surface in created on the side we work on and yellow on the opposite side.

 

In Mesh- Classic Mesh

1) Apply Perimeter Length of 5 in PERIMETERS option in CLASSIC MESH Module. 

2) Measurement check-up.

• Check measurements for Quality check purpose and alter the lengths if required by using MACRO Cut option.

3) Check the Length around the corners and other holes to make perimeters EVEN. Numbered.

4) Slide the perimeters of Holes parallel to any sides of the component for easy mesh creation.

5) Once the HOT points are arranged, Mark the components from MARK/UNMARK option from HOT POINTs in Classical Mesh Module.

Meshing Process:

1) To set Mesh parameters

• We have to set Mesh Parameters to 5 from Utilities Module set  

2) Crete Properties ID

• We have to create new Property IDs for all the new Mid surfaced Planes and assign thickness to each of them.

3) Mesh creation using Best mesh method.

• Apply Best mesh tool to mesh the surfaces.
• Mesh the components individually.
• Alternate to Best Mesh we have Free Mesh to have best outcome.
• We can divide the planes of the structure into several small parts to form MACRO REGIONS to mesh the structure for conveniently.

4) Other Operations to be executed to fulfil Quality Criteria and to remove Tria Elements are: -

• RECONSTRUCT -
• This tool is used to Auto regenerate the mesh by eliminating the Trias as well as by satisfying the Quality Criteria.
• It tends to change the structure of mesh of the selected region completely.
• SMOOTH –
• This tool is used to Adjust the Quads as well as Trias in a more linear flow for the mesh without changing the structure of the mesh.
• SPLIT –
• This tool is a combination of SWAP tool and SPLIT tool.
• It is used for Splitting the Trias at the corners as well as at the perimeters to form uniform mesh patterns.
• IMPROVE -
• This tool is a combination of both SMOOTH and RECONSTRUCTION tools.

5) Once the complete mesh is achieved, It is very important to join the CUTS formed by using CUT tool in MACRO by maintaining the ‘KEEP MESH’ option from the OPTION list.   

6) After joining the cuts, the left-over HOT POINTS has to be deleted to form proper mesh.  

7) Create Part ID for the Meshed Elements and assign thickness as per the conditions.

8) To view the Mesh in Soils State Draw shell as solid

• Open Quality criteria [F12] and switch to Presentation parameters Tab.
• Switch On ‘Draw Shell as Solids’

9) Release the Elements from RELEASE option in ELEMENTS Module.

10) Switch OFF the Geometry Tab in Visibility Module to get only the complete meshed surfaces.

 Learning Outcome :

Since the given component is partially symmetrical, We could delete the components those are symmetrical to other part for avoiding more time in meshing the components.

Copy the meshed part and paste it symmetrically using ‘symmetry’ Option from TRANSFORM tool.

CONCLUSION :

To create uniform flow of mesh around the elements by achieving Quality criterias and reducing maximum number of Tria elements in the meshed zone.

We also try to avoid the rotation of Quads as well as Opposite trias in the meshed components.