Hemming and Surface Meshing of Car Hood for Structural Analysis Using ANSA

OBJECTIVE:

The key objective is to do Hemming and Surface meshing of Car Hood geometry for Structural Analysis by extracting out their midplanes with the target element of size 5mm.

Hood can also be called as the Front Panel of a car. In layman language, we usually say Bonet of car.

Hemming is a metalworking process in which a sheet metal overedge is rolled flush onto itself.

PROCEDURE:

1. Import the .STP file in the ANSA workspace.
Here we know that other than .ANSA file we can import. The ANSA software accepts many different extensions and converts into .ANSA format.

2. Examine the geometry properly and after that remove unnecessary elements & perform Geometry check and acc. to it eliminated all the topological Errors.
Again geometry checks and makes sure there are no Errors like needle faces, Penetration Intersection, etc.

3. Now, there are two different parts we have. Accordingly, we have to Create Mid Surface from the Inner panel and as well as Outer panel.

For that, we can use two commands;
One is the Offset Command and Assign the Offset value (0.75/2) because of the thickness of both the Panels is 0.75.
Another is Mid. surface command in that skin option we use here.

We do all this work for both the panels but one by one.

Firstly we do with the inner panel and after that, we do for the outer panel.

4. Isolate only the middle part which we offset and eliminate the geometry errors on that also. Check for the Symmetry of the panel with the help of Rm. Dbl (Remove Double command) by applying Symmetry Factor 100% with a tolerance of 0.05 and we get to know that, it is symmetrical w.r.t. to the middle line.
For eliminating all the errors we do one thing, we delete the half portion and remove errors in the remaining half and after doing that we just make a copy of that part other side and paste the geometry with each other. It reduces 50% errors and consumes less time.

5. Apply all the Quality Criteria which is given and Eliminate errors According to it.

6. Before doing symmetry we Mesh the right part of the panel then make a copy to the left side. Now we get mesh on the whole part. we get the Associate mesh.
The Target element size should be 5 mm.

7. Isolate mid surface of both the panels. Assign the different PIDs to both of them & give a thickness of 0.75 mm.
Make an intersection between them properly wherever it required and Paste the cons & make the triple con between them.
This 6th point is to define the Hemming operation itself. After the intersection which we get that part is called Hemming Part of the car hood.

8. By using the I-NOT option, Isolate that Hemming portion of Hood and assign the different PID to it and with that, we also have to assign a thickness of 2.25 mm to that hemming part.

9. Hemming thickness formula (H.T.F)

H.T.F. = (2*O.T.) + I.T. (O.T. = Outer panel thickness & I.T. = Inner panel thickness)
H.T.F. = (2*0.75) + 0.75
H.T.F. = 2.25 mm
Hemming is just a representation of Outer thickness.

10. Visible the mid surface of the Inner panel & Outer panel and Hemming part.
Just make sure for rectifying all the Topological & surface mesh errors and about Quality criteria like skewness, min. length, max. length and all other parameters which are given.

CONCLUSION

• Mainly here we understand the Hemming process.
• How to extract the midplane from a Geometry with the help of OFFSET command & MID SURFACE command both.
• How to assign thickness and material Id. to any component using PID command.
• How to fulfill the Quality Criteria which require and rectifying and resolving the errors accordingly, which occur in between the quality criteria.

Google Drive link:

https://drive.google.com/open?id=1zxCyIqfJhnLBt5JhBDIJh0Vl1XPSlxsI