Meshing for Structural analysis of HOOD
Objective – To remove topological errors, creating the Mid surface and Hemming the inner and Outer Panel of hood. Meshing the hood for Structural analysis as per the Quality criteria given below.
Target length – 5mm
|
S.N |
Quality Criteria |
Value |
|
1 |
Aspect Ratio |
3 |
|
2 |
Skewness |
45 |
|
3 |
Warping |
30 |
|
4 |
Taper |
0.5 |
|
5 |
Min. Length |
3mm |
|
6 |
Max. Length |
7mm |
|
7 |
Min angle Quad |
45 |
|
8 |
Max angle Quad |
135 |
|
9 |
Min angle Tria |
30 |
|
10 |
Max angle Tria |
110 |
|
10 |
Tria % |
15 |
Solution – First after opening the hood in ANSA we hide the outer hood panel and see only the Inner Hood panel.
-We see that there are single cons on the surface. In order to check the topological errors on the surface need to geometry check the inner Hood Panel.
-Clearing the topological errors by deleting the unwanted surfaces. And using TOPO option in FACES to paste the cons. Even after operating TOPO options there are still some red cons. This is because there is a surface missing.
-Creating a new surface with new in faces option.
-Now we also see a cracks at the latch area on the inner panel. We clear the cracks using Topo option.
-Again we run the geometry checks for the Panel we see that all the errors are removed.
- Also changing the PIDs.
- Now in order to create the mid surface of the inner hood panel there are two options, first is offset and second is midsurface in faces.
-Offset is generally used when the geometry of the element is not uniform while midsurface skin is used for a uniform geometry.
-For the inner panel we use offset and select the entity, we see the direction of the offset, in our case it is in the opposite direction so we give offset distance in negative sign and half of thickness.
-Thickness is 0.75 mm so we give fraction as 0.75/2. And Confirm the command.
- We see the mid surface been created in the middle. Now to extract the we can use Inot in ENT mode and then use neighbour option to see the mid surface.
-We create a new PID for the created surface.
-Now we store the lock at inner panel mid surface.
- we open the outer panel of hood to clear the topological errors but after geometry check we see that there are no errors.
-So to create mid surface we use Mid surface skin option under faces.
-PID is created. Thickness for both inner and outer mid surface is given as 0.75 mm.
-Hemming is a process where inner and outer panel of the hood are joined together by sandwiching the inner panel in between outer panel.
-Hemming process is done for all four closures of a Car.
-Now for FE analysis we project the sandwiched edge of outer panel on to the inner panel and also on the outer surface of outer panel.
-After projecting the outer edge on both the panels we delete the outer panel from the edge to the fillet section.
-Now we join the two projected surfaces on panel which creates a triple con. But in this case the triple con is part of the hemming process and is required.
-After creating a triple con we can hide surface and create a new PID for the Hem surface. The thickness of the hem surface is given by formula as twice the outer thickness plus inner thickness.
- So hem thickness is given as 2.25 mm.
-After creating three separate PIDS for Hem surface, Inner and outer hood panel we check for geometric errors and clear them if they are there.
-Meshing
-Moving to Mesh mode we change the length of the Hood to 5 mm.
-Changing the mesh parameters.
-Under mesh generation we use Spot Mesh option to generate a mesh for all three PIDs.
-After creating a mesh we go to quality criteria and switch on the above parameters. Also changing the values according to table. And apply to the mesh
-We see a total of 3500 elements are off.
-We clear the mesh using reconstruct reshape, swap, split and MV surf to clear all the off elements.
-After clearing all off elements and arranging the mesh flow such that there are no opposit trias.