Structural analysis mesh for a side door panel in ANSA

OBJECTIVE:

1. To perform Structural meshing on side door panel of an automobile using the various tools in the ANSA software and meshing it with the given quality criterion.
2. Perform manual mid surfacing method for the model using various PIDs and also mesh them to the given target length and the quality criterion.
3. To create three files and compare them in their result for the FE extraction and mid surface generation

PARAMETERS: The parameters for the given model are as follows

1. Mesh target element size: 5mm
2. Quality criterion to be followed while meshing

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
11	Tria %	15

Side door panel information

Unlike other types of doors, the exterior side of the vehicle door contrasts in its design and finish from its interior side (the interior part is typically equipped with a door card (in British English) or a door panel (in American English) that has decorative and functional features.

The exterior side of the door is designed of steel or other material like the rest of the vehicle\'s exterior. In addition, its decorative appearance, typically coloured with a design, is intended to match with the rest of the vehicle\'s exterior, the central purpose being to add to the overall aesthetic appeal of the vehicle exterior.

There are various parts of a door that an automobile manufacturer assembles for structural integrity, crash testing, better fitting etc.

1. Door latches
2. Door switched and locks
3. Windows
4. Door brakes and stays
5. Auxiliary parts like door rubber and sealant

PROCEDURE:

1. Firstly, when we import the CAD file into ANSA, there are always topological errors that need to be fixed. These errors are caused due to the transition of the CAD geometry from the designing software to ANSA. For this model the side door panel had a lot of errors such as missing faces, unchecked faces, topological errors, triple cons and singe cons as well.

1. Now we need to fix the errors in the geometry. We can use various commands that we have been taught that would help us clean the geometry of the surface.

For this challenge the geometry provided to us is divided into 5 models. Each model has its own geometry and a different mid surface formation but the same quality criterion.

1. When we encounter a single con that means it can either be a junk surface or it could be a con that has not been attached to a surface. In both cases it is advisable to inspect and create a new surface which connects the model into a double con.
2. When the errors are caused due to a triple con. These errors generally occur when there is a surface that is in contact with three different surfaces. Thus the ANSA processor gives is a triple con error when we check it in the geometry checks. In this error generally we need to delete a surface that has been attached to the model which Is not essential to us so we can delete this to obtain a double con.
3. Finally, are those surfaces which can be called as cracks or needle faces and always cause problems while meshing and also post processing. For these you need to revisit each of them and individually either delete the needle faces and create a new face or you need to insert hot points and break the con so that is deletes the needle face itself.

Figure 1: Clean side door panel geometry

Figure 2: Geometric checks complete

4. After the geometric clean-up now, we can move on to the mid surfacing of the model. For this we need to find out the thickness of the model.

For this side door panel, I used the weld spots feature in the hot points tab. As this geometry is not uniform in length and it is difficult to measure the length at two nodes, we have to use weld spots for such geometries. In this we used the weld spots and then selected a surface on which the weld spots were put on. Then by using the project command in the hot points we project the weld spot to the opposite surface. After this we use the measure tool to measure the distance between the two weld spots and that would be the thickness.

Figure 3: Thickness measurement of the side door panel

5. For the manual mid surfacing method, we have used offset command inside faces tab in ANSA. This command lets us choose the surface we want to offset. Here we can make use of the selection bar in ANSA. The command feature in the selection bar allows us to select the surfaces which have the feature angle more than 40 deg. This allows us to select the surface which we can easily offset. After we select the face and give offset, we can then choose the offset value which is generally half the value of the thickness.

6. For the auto mid surfacing we use the mid surface command in the faces tab of ANSA.

In the mid surface command, we use the option casting and then choose the surface we want to mid surface. This command helps us not only creating the mid surface but also helps us in extracting the FE from the geometry mesh.

7. For this model, I used middle to mid surface the ribs and then used the extend command to connect all the mid surfaces to the existing surfaces already produced by offset.

For this project we need to show three files,

1. Side door panel with auto mid surfacing
2. Side door panel with manual mid surfacing
3. Side door panel with combined method of mid surfacing

SIDE DOOR PANEL AUTO MIDSURFACE

Figure 4: Automatic mid surfacing for the side door panel

Figure 5: Quality check for atomatic mid surfacing

SIDE DOOR PANEL WITH MANUAL MID SURFACING

Figure 6: Manual mid surface of the side door panel

Figure 7: Quality checks for manual mid surfacing

SIDE DOOR PANEL FOR COMBINED METHOD OF MID SURFACING (AUTO AND MANUAL METHOD)

Figure 8: Mid surface with the combination of auto and manual method

FIgure 9: Quality check for the combined mid surface

COMPARISON

According to my observation the manual mid surface method gave the best result as to the quality of the mesh. The manula mid surface has a better flow of mesh accros the model and also has lesser number of tria elements than the other two.

Another advantage that the manual method provides is the complete mid surfacing of the model with respect to the ribs. The auto method was not able to potray the ribs at all which made it not such a good choice for this geometry. In turn there were some surfaces that the auto mid surface was not able to project properly and this it created alot of quality errors.

Only disadvantage the manual method has is the time consumption as opposed to the automatic mid surfacing method. The automatic mid surfacinig method took approximately 3 minute whereas the manual method took about 20 minutes while mid surfacing the ribs.

CONCLUTION:

The mid surface of all the threwe models have been extractedand the quality errors have also been fixed. The link for the files of this project has also been shared

LINK: https://drive.google.com/open?id=1xWUEhRhWUh607wQ7SoNVD0XNr0thjEKY