Meshing of Hood Model

Meshing of Hood Model

Objective:

Performing Geometry Clean-up to remove any topological error, extracting mid-surface of every sub part and subsequently meshing the hood model using the following quality criteria using ANSA.

Sr 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
12	Tria Percentage	15
13	Tria per node	2

Procedure:

1. The first step before beginning involves checking that the model is in .ansa or .stp format. ANSA can read file and work on in this format.

Fig: Hood Model

2. The next step is crucial step going ahead, that is checking the given file is of good quality. We need to ensure the model is free from any topological error using Geometry Check-Up. We need to use geometry Check-Up to see the numbers of existing errors.

Fig: Geometry Check-up

We need to clear all these error before proceeding ahead. Once cleared the check geometry dialogue box will give green signal on execution.

3. After this step we will check for the number of parts in the given model. We can do this using Properties ID

After executing it showed 5 properties ID which is equivalent to 5 sub-part

Now we will rename this ID to its actual name for own convenience and understanding.

The following are the sub part:

1. Outer Panel
2. Inner Panel
3. Hinge 1
4. Hinge 2
5. Hinge 3

Fig: Renaming properties ID

Fig: Outer Panel Fig: Inner Panel

Fig: Hinge 3 (Left)

Hinge 2 (Top right)

Hinge 1 (Bottom right)

4. After geometry clean-up and subsequent renaming of part, we proceed to do what is most important thing for meshing, extracting mid-surface. We extract mid-surface as we mesh on it. But for generating it, we need to know the thickness of individual sub part

Fig: Measurement of each parts

The following are the thickness of sub part:

1. Outer Panel = approx. 0.75 mm
2. Inner Panel = approx. 0.75 mm
3. Hinge 1 = approx. 1.20 mm
4. Hinge 2 = approx. 1.20 mm
5. Hinge 3 = approx. 1.20 mm

The mid-surface for the outer and inner panel will be at 0.375 mm and for hinges will be at 0.60 mm. One thing we need to make sure while extracting mid-surface is that the model should be oriented using Orient command. We use Offset command to extract mid-surface of entire feature using Feature Area command. We will again do a geometry check up to make sure each part are free from any error. And once this is done we will assign each part its properties ID using Set ID command.

The following are the extracted mid-surface:

Fig: Mid-surface of Inner Panel

Fig: Mid-surface of Outer Panel

Fig: Mid-surface of Hinges

Now we can observe that the outer panel is completely symmetrical and inner panel is almost symmetrical. We will only take the half portion for outer panel.

Fig: Halved Symmetrical Mid-surface of Outer Panel

For inner panel, we will delete all half of the faces that are symmetrical.

Fig: Halved mid-surface of Inner panel

We need to select the asymmetrical face and assign it to different properties ID.

Fig: Mid-surface of Asymmetrical part of Inner panel

Fig: Halved Symmetrical mid-surface of Inner panel

5. After the mid-surface is generated we can go ahead with meshing of each parts

But for some parts that are certain areas where we need to resurface the part or defeature certain areas to get the best of both world. Resurfacing is done for good mesh and mesh pattern. Defeaturing is done to preserve the function of the part while also getting the best mesh result.

Fig: Resurfaced mid-surface of Inner panel

Fig: Resurfaced mid-surface of Outer panel

Fig: Defeatured hemmed portion of Outer panel

We need to understand that our Outer panel outer portion is hemmed over inner panel

Hemming is a sheet metal forming process in which sheets are joined by bending it to 180°. We have defeatured to compromise for better result during analysis.

Fig: Hemming Process

6. Lastly, the meshing of each sub part is done individually. Before that we need to set mesh parameter, quality criteria and presentation parameter

Fig: Setting Mesh Parameters

Fig: Setting Quality Criteria

Meshing is done using BEST command under Mesh Generation. But there are areas where the mesh flow will not necessary be good. We need to improve mesh flow and pattern in such area to make the mesh more refined. The trias element at the perimeter and the edge are removed for better result and to avoid any failure going ahead. All the off elements that are not fulfilling quality parameters are resolved individually and the opposite trias are taken care of by swapping their position until they are unopposite to each other. All of these are done to ensure the better result and avoid any sort of failure. This improving task is done using series of command such as Reconstruct, Smooth, Batch Mesh, Split, Swap, Paste, Cut, EdgePerimeter, Join, etc.

Fig: Meshed Inner panel

Fig: Improved mesh of Inner Panel

Fig: Mesh of Outer panel

Fig: Improved Mesh of Outer panel

Fig: Mesh of Hemmed portion Fig: Improved mesh of

hemmed portion to preserve it function

Fig: Mesh of Hinge 3 Fig: Improved Mesh of Hinge 3

Fig: Mesh of Hinge 1 Fig: Improved Mesh of Hinge 1

Fig: Mesh of Hinge 2 Fig: Improved Mesh of Hinge 2

After meshing, the symmetrical portion are need to be brought again. This is done using Copy command under Transform.

Fig: Transformed Mesh of Outer panel

For Inner panel we will first recall asymmetrical portion of the panel and then again we will use Copy command under Transform

Fig: Symmetrical half portion mesh of Inner panel along with asymmetrical face

Fig: Transformed mesh of Inner Panel

The following are the final mesh consisting of all subpart for hood model

Fig: Mesh of Hood Model

Fig: Mesh of Hood Model

Fig: Mesh of Hood Model

Result:

Quads = 93659 (98.63 %)

Trias = 1305 (1.37%)

Total = 94964

Conclusion:

The meshing of Hood model after clean-up of topological error is done.

Link of Meshed Hood Model:

https://drive.google.com/drive/folders/1H8vh9fYnk3zYA9B06oQsHgvg7A1T0vJE