2-D Meshing of Car Hood using ANSA

Objective:

For a given component (car hood) check for the geometrical errors and mesh with the given element quality criteria and assign required thickness post meshing.

Method:

1. Import hood model into ANSA.
2. Geometry clean up.
3. Mid-Surface extraction.
4. Setting PID and thickness assignment.
5. Defeaturing as required.
6. Meshing.

The meshing needs to be executed against the below given quality criteria and needs to fulfill the following requirements:

• Proper mid-surfacing
• Good mesh flow
• No OFF elements
• Thickness assignment

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

Method:

1. Import hood model into ANSA.

Input model contains four major parts:

1. Upper Hood
2. Lower Hood
3. Bottom Latch
4. 2 - Side Latches

2. Geometry clean up.

Below shown geometry errors can be detected by running geometry check available in tools tab.

1. Use Auto-Fix to resolve errors.
2. If any error resolution is unsuccessful in auto mode then use manual method for cleanup by using release and TOPO tabs in Faces section available in TOPO mode.

3. Mid-Surface extraction

We extract the mid surface of upper hood, lower hood, bottom latch and side latches respectively by using Offset tab in Faces section and select the following faces and provide required direction and offset distance in addition with Feature Angle command.

4. Setting PID and thickness assignment.

After extraction of middle surface of the given components we assign new PID and thickness to the parts by using Set PID tab under faces tab in TOPO:

1. Select Faces and Shells option.
2. Right click and select New à Pshell
3. Assign PID and Thickness

5. De-featuring as required.

De-feature model and suppress insignificant cons to further clean geometry and avoid any quality and minimum length failure.

6. Meshing of the component.

Now we proceed with meshing of the components:

1. Select MESH tab from upper right-hand corner
2. Press F11 to open quality tab and enter the given parameters
3. Open Mesh Parameter tab and enter target, minimum and maximum lengths.
4. Make user defined cuts using Cut tab as needed to get a good mesh flow.

1. Use Best mesh tab under mesh generation tab and select faces to generate mesh.

Final Meshed Model

Now, we will try to eliminate ‘Trias’ elements as much as possible in corners and opposite faced and we must completely eliminate any ‘Rotating Quads’ from the model to achieve better mesh flow.

Conclusion:

The complete car hood has been 2D - meshed successfully using ANSA workbench taking into account all the quality parameters and required mesh flow can be observed.

Learning Outcomes:

1. Geometry clean up and error fixing.
2. Performing topology
3. Creating mid-surface and PID assignment.
4. Importance of mesh quality parameters.
5. Model meshing against required quality criteria.
6. Removing tria elements and rotating quads using ‘Split, Swap, Smooth, Paste, Reconstruct and Reshape’ to achieve required mesh flow.