PREPROCESSING THE DASHBOARD SUB PARTS FOR STRUCTURAL ANALYSIS USING ANSA

PREPROCESSING THE DASHBOARD SUB PARTS FOR STRUCTURAL ANALYSIS USING ANSA

OBJECTIVE:

• To clean up the geometrical errors in the dashboard sub-part model.
• To generate mid-surface.
• To mesh the model under the required quality criteria.
• To assign thickness to the model.

GIVEN MODEL OF THE DASHBOARD SUB-PART:

QUALITY CRITERIA:

S.No	Quality Criteria	Value
1	Target/Average length	4
2	Minimum Length	2
3	Maximum Length	6
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
10	Tria Percentage	15

PROCEDURE:

1. GEOMETRY CLEAN-UP:

• Import the CAD model in ANSA.
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• The length option in the mesh tab is used to refine the geometry by changing the perimeter and macro length of the model.
• The target length is 4mm. So enter a value of 4mm as perimeter and macro length.
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• Use the topo option to connect the surfaces together.
• Check for the geometrical errors using the checks manager. Clean up the geometrical errors using the auto-fix option. Use manual clean-up for other geometrical errors which cannot be auto-fixed.
• Likewise, remove all the geometrical errors and verify that all the errors are cleaned up.
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2. MID-SURFACE GENERATION:

• Correct the orientation of the model.
• Measure the thickness of the model at different locations.
• The Dashboard model is lengthy and has thin-walled parts. So creating a mid-surface shell model is favourable.
• Reasons to use mid-surface shell mesh are:
  • The accuracy of the end result can be way off with solid mesh elements.
  • The solid mesh approach, which needs 3 to 4 elements across the thickness, results in a huge amount of elements and long running times.
  • Meshing nasty geometry with solid mesh elements needs preparation too.
  • Post-processing of a huge number of solid element simulations takes ages.
  • The shell mesh approach creates a fast-running accurate simulation.
• The model is too complex for the automatic mid-surface generation.
• Generate the mid surface manually using the offset and middle commands.
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• Create different PIDs and locked views to handle the required views of the model.
• Assign thickness in the PIDs created.
• Connect the geometrical features like fillets, ribs and other projections in the model using the extend, intersect, topo and paste options.
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• Clean-up the geometrical errors in the mid surface created.
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• Switch to the PID Views.
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• The ribs and fillets are captured in a way to satisfy the quality criteria.
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• Use the copy option to copy the ribs and projections wherever required.
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• Compare the mid surface created with the original model and check for any miss alignment or missing surfaces.
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3. QUALITY CRITERIA:

• Assign the required quality criteria and mesh parameters.
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4. MESH GENERATION:

• The dashboard model is too large and has lots of small ribs and projections with a different thickness which needs a lot of time for surface by surface clean up and meshing.
• The batch mesh method can be used to clean up and generate mesh on the model automatically as per the quality criteria.
• This is an ideal tool for cleaning up the geometry for the target length specified. This can save a lot of time.
• After applying this method, the mesh generated can be erased if found to be unsatisfactory.
• Mesh the model using the best, spot mesh and free mesh generation tools.
• Use the reconstruct option to improve the element quality.
• Use the smooth option to improve the mesh flow.
• Use the PIDs and the locked views to switch between surfaces.
• The model is meshed using quad and tria shell elements.
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• Meshing the ribs and other features:
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5. DRAWING SHELLS AS SOLIDS:

Link to the model: https://drive.google.com/file/d/1FMdn9uNnIB9ThnDUKJ4KGpoCLFb5Ur3N/view?usp=sharing

CONCLUSION:

• The dashboard sub-part model has been meshed successfully as per the required quality criteria.
• The mesh flow has been maintained.
• The tria element concentration is strictly restricted under 5%.
• There are 79402 shell elements in the model out of which 3961 elements are tria elements.