2D Meshing of the Car Hood using ANSA Preprocessor

Challenge Name:2D Meshing of a Car Hood.

Aim:

To fix the Geometric Errors in the give model and create the 2D meshing with proper mesh flow considering all the quality criteria given above.

Procedure Followed:

1)Import Model into ANSA

2)Geomterical Clean up and Topology

3)Extraction of Mid Surface

4)Assigning New Property ID(PID) to the Mid Surface

5)Defeaturing as per requirement

6)Meshing

Given Quality Criteria:

Sl No	Quality Criteria	Value
1	Target Lenghth	5
2	Minimum Length	3
3	maximum Length	7
4	Aspect Ratio	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

PROCEDURE

Step1)Import Hood.STP File in to the ANSA

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About Input Model:

• Given Model has a very Less Thickness of 0.75mm
• Model has 4 Different properties names as below

a)Upper Hood

b)Lower Hood

c)Side Latches

d)Center Latch

2)Geometry Cleanup And Topology

• The Given model is subjected to the geometric Check and Checking for the errors.

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Now the Geometry is Cleaned up and ready for Mid surface creation.

3)Extraction of Mid Surface

In this model the mid surafces of all the 4 components are taken seprate and manually

• Select "Offset" Command under the Faces.

• Select the faces for which the mid suraface to be extracted (Preferred to Use Feature angle Command )

• Give the Offset value in the window popup on your screen.

• Mid Surace Created and will be Indicated by the Red Line in the Geometry.It is extracted from the Geomtery by using INot and PID Region Command.Mid Surface of Top hood is shown below.

Like wise the mid surface has been created for Lower Hood and Latches Component Seperately and attached the picture for the reference below.

a)Mid Surface of Side Latches

b)Mid Surface of Center Latch

c)Mid Surface of Lower Hood

Step 4)Assigning New Property ID(PID) to the Mid Surface

Once after extracting the mid surface,each component should give the new property ID and renamed it acordingly and also colour coding should be given.

• After Creating the Mid Surface ,Click on "Set PID" Command under Faces and Select "Faces/Shells" Command as shown in th picture below

• Property Tab is Popup on the Screen as shown in the image below.

• To assign new property Right Click on the property Tab,Go to "NEW" command and clicl on "PSHELL". New Property Card will be popup on the screen as shown below.

• Enter the specification of the component and Assign the thickness of the component and give the colour coding .Press OK.New Property ID Created for the Mid Surface.

Like wise for All Component Property to be assigned seprately and Indicated by Colour Code.

Hence the Assigning New Property ID to the Mid surface is Completed.

Step 5) Defeaturing as per requirement

Defeaturing is a technique to remove unnecessory Surface and radius which our CAD Model contains may detailed features because of manufacturing constrains.

In this Model Minimum Element lenth is 3mm.So all the Surfaces beyond the Minimum lenght should be removed for better quality of meshflow.

Step 6)Meshing

• Go to "Mesh" Mode from "Topo" Mode.
• Now have to assign the Mesh Parameters.Go to "Mesh Parameters" Command and enter the Values as shown below:

• Enter the Quality Criteria Given.Go to "Quality Criteria" Command(F11) and Enter the Quality points given

• Make a User Cuts using "Cut" Command under Macros to get a Good Mesh flow as shown in the picture below.

• Mesh the Component.

"Best" Meshing command to be used for this model

Avoid Rotating quads,trias for good Stress Propogation.

Meshed model shown below:

Thus the meshing is completed for the Componnet and the image is as shown below.

• Meshing of Top Hood(Thickness-0.75mm)

• Meshing of Lower Hood(Thickness-0.75mm)

• Meshing of Latches(Thickness-1.2mm)

Thus the meshing is completed and visualize in the solid representation option in the presentation Parameters.Overall Meshed Component is as below.

Now there are many Rotating Quads and Trias are there in the meshed Component.Let us see How to remove those Trias and Rotating Quads.

1) Steps Followed to remove Trias Using "Paste" Command

a)Find the Opposite Faced trias in the Meshed Component.

b)Use "Paste" Command under grids and Select the nodes to be pasted as shown in the fig below.

Press Middle mouse Click for Confirmation.

c)Two opposites faced trias are eliminated.

2) Steps Followed to remove Trias Using "Split " Command

a)Find the trias facing to the free edges or two traias facing in same direction in the Meshed Component.

b)Use "Split" Command under Elements and Select the Path on which direction tria should move as shown in the fig below.

Press Middle mouse Click for Confirmation.

c)Tria facing free edges has been removed.

3)Removing Rotating Quads

a)Find the Rotating Quads in the meshed component as shown in th fig.

b)Split the Rotating quads into two trias as shown in fig.

c)Move the Trias to the Right Using "Swap" Command

Thus the rotating quad is convertd into two traias and it can be removed by "Paste" and "Split" Command.

Results

The Given Car hood is meshed successfully considering all the quality criteria given and thickness is assigned and thre component can be proceed to apply the Boundry conditions.

Learning Outcomes:

1)Geometrical Cleanup and checking for error and fixing it.

2)Releasing the Triple Cons.

3)Creating Midsurfacing and Assigning New PID.

4)Meshing of a Component according to the Quality Criteria.

5)Removing Trias using Split/Swap and Paste Command.

6)Removing the Rotating quads by Split/Swap Command.

Conclusion:

Thus 2D mesh is created for the given hood component of a car according to the given element quality criteria using ANSA workbench.