Week 7- Meshing of Backdoor Challenge

Week 7-Meshing of Backdoor Challenge

1. Aim

• To Generate a mesh on a given model after a proper geometry cleanup and mid-surface generation using Hypermesh.
• Ensure the generated mesh obeys the mentioned quality criteria and the corresponding thickness of each surface assigned to the mesh.

2. Objective

• Import and perform a geometry cleanup on the given model using Hypermesh.
• Assign thickness and generate a Proper mid-surface with the proper technique.
• Mesh the generated mid-surface and reconstruct the mesh to satisfy the following quality criteria.
• Model Checks

Quality Criteria

Sl No:	Quality Criteria	Value
1	Target Element Length	5
2	Aspect Ratio	5
3	Skewness	45
4	Warping	15
5	Taper	0.5
6	Min. Length	3
7	Max. Length	7
8	Min. Angle Quad	45
9	Max. Angle Quad	135
10	Min. Angle Tria	30
11	Max. Angle Tria	110
12	Tria %	15

Fig 1: Isometric View Of Model.

3. Procedure

Step 1: Importing the File

First We have to import the file to hyper mesh. Here, the file is in IGES format.

• File >> Import >> Geometry >> Browse the file location >> Select The File >> Import.

Step 2: Geometric Cleanup and Extracting Midsurface.

The model contains 3 separate parts and the model it will be assigned as a whole single model. So we have to transfer them to 3 different components. For that, we have to create 3 more components and transfer each model by,

• Tools >> Organise >> Select Surf >> Select Dest Component >> Move.

Fig 2: Component Name: Front (ID: 1)

Fig 3: Component Name: Bottom (ID: 2)

Fig 4: Component Name: Back (ID: 3)

Then after the auto cleanup, we have to extract the mid surfaces for each component. In this case, we use the manual method, that is offset option to generate the mid surfaces. For that, we need to measure the thickness of each component. By taking measurements in different places of each component, the measured thicknesses are,

Sl No.	Component Name (ID)	Thickness (Units)
1	Front (ID: 1)	0.75
2	Bottom (ID: 2)	0.75
3	Back (ID: 3)	0.6

So the offset value will be half of the thickness value, also check the normal and adjust the normal if it is required.

• Geometry >> Surface Edit >> Offset >> Select The Face >> Surface-Duplicate >> Input Offset Value (Thickness/2) >> Check For Normal (Reverse If It Is Required) >> Offset.

Repeat the procedure for all components and extract the mid surfaces separately.

Fig 5: Mid Surface Extraction By Offset

The mid surfaces can be cleaned by toggling unwanted lines or using washer splits. All mid surfaces are symmetric, so we can mesh half and duplicate it and reflect the other side.

Step 3: Property, Material, Measuring Parameters and Quality Criteria

We already measured the thickness, so by using those values we can create and assign properties to the mid surfaces. Create material for those properties. Also, add quality criteria and measuring parameters.

Fig 6: Property and Material

Fig 7: Measuring Parameters

Fig 8: Quality Criteria

Step 4: Meshing the Surface

Because of symmetry, one-half of the mid surface is only needed for the meshing. So the other half will be masked (F5 >> Mask the Unwanted Region). The remaining part meshes using

• 2D >> Automesh >> Select Surface >> Ok.

Fig 9: Generated Mesh (ID: 3)

The mesh flow should be improved especially in feature areas. By editing numbers, or using options like 'Rebuilt', and 'Edit Element', we can improve the mesh flow.

Check the 'quality index', if any elements failed for quality, they should be addressed by cleanup tools provided by the quality index. After that, use the Reflect-Duplicate option to mirror the mesh to the other side and it completes the mesh for the following mid-surface.

Fig 10: Final Mesh (ID: 3)

Repeat the procedure for other mid-surfaces to generate mesh on those mid-surfaces.

Fig 11: Final Mesh (ID: 2)

Fig 12: Final Mesh (ID: 1)

Using 'Tools >> Check Elements' we can draw plots for each 2D quality criteria.

Step 5: Model Checks

Check For Free Edges And Equivalence

• Tools >> Edges >> Select Elements >> Adjust The Tolerance Value (~0.5) >> Find edges. >> Delete Edges >> Preview Equivalence >> Equivalence.

Fig 13: Edges And Equivalence

Check For Connectivity and Duplicates

For Connectivity

• Tools >> Check Elements >> 2D >> Connectivity.

For finding duplicates,

• Tools >> Check Elements >> 2D >> Duplicates.

Fig 13: Connectivity and Duplicates

Check For Normals

• Tools >> Normal >> Elements >> Color Display >> Vector Display >> Size= 100 >> Display.

If any of the vectors have opposite directions, it can be corrected by Using the 'Adjust' option.

Fig 14: Check For Normals

Check For Penetration and Dependency

For penetration/intersections checks,

• Tools >> Penetration >> Select Elements >> Check

For dependency checking,

• Tools >> Dependency >> Select Elements >> Dependency

Fig 15: Check For Dependency

Fig 16: Check For Penetration

Fig 17: Final Result

4. Conclusion

• The mid surface of the given model is generated separately by components, assigned properties, and materials and adds quality criteria and target element lengths for every one of the components.
• The meshing and reconstruction of a generated mesh of each component are completed.
• Model checking is finished.

5. Results

• For the given model, the mid-surface is extracted and mesh generated. The generated mesh satisfies the following quality criteria and the model checks are completed.