Week 3 - 2D meshing for sheet metal

AIM

To fix Geometrical Errors and take the mid surface of the 2D elements and mesh them according to the given quality criteria.

Given Quality Criteria:

S.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
10	Tria Percentage	15

Procedure

Step1- Import the model into ANSA

Open the file Hood.STP in ansa

The given model has 4 different parts -

• Upper Hood
• Inner Hood
• Latch
• Hinges

Step 2 - Geometry Cleanup

• In the check manager we select "geometry" and run the check, the geometrical errors then pop up on the screen.

• The errors are removed by deleting needle faces, fixing up single cons, generating new faces where cracks appear and using auto-fix wherever required.

Step 3 - Creating Stored locks for ease of access

Step 4 - Mid Surface Extraction

Method used - Faces - (offset)

• All 4 parts were extracted separately by the faces offset method.
• Under the faces, option choose the offset command :

• Select the faces on which you want to apply the offset:

• Enter the thickness value at which you want the mid surface.
• To finalize click the middle mouse button and the mid surface will be created.
• The mid surface will be shown by red lines and is extracted by using the ! not command.

Mid Surfaces are as shown below :

Outer Hood Midsurface

Inner Hood Midsurface

Hinges Mid Surface

Latch Midsurface

Step 5 - Assigning PID to each part

• To assign new properties, click on the properties tab.
• Right-click and select new "PSHELL", assign the thickness and PID NO. as shown

• Assign new PID to each mid surface with the appropriate thickness.

New PIDS assigned to all components as shown below:

Step 6 - Defeaturing

To satisfy the min. and max. length criteria we need to suppress the FE model as per requirements, this is known as defeaturing of the model.

Step 7 - Meshing

• we switch to the meshing mode located at the top right-hand corner.
• Assigning Mesh Parameters - Mesh parameters are assigned in the mesh properties tab as shown below:

• Next, we enter the values of the quality criteria given to us - press F11 or open the quality tab and enter the values as shown :

• Use project cuts to get a good mesh flow.

Meshing - under mesh generation tab use the best mesh command as shown below:

Meshing has to be carried out.

Meshed Model has been shown below separately:

Step 8 - Refining the Mesh

• For refining the mesh we need to get rid of the tria elements near features and have the maximum possible quad elements in the model.
• Commands used- Split, Paste, Swap as shown below :

Paste- tria elements can be removed which are facing each other.

Split - used to split tria elements into no of tria or quad elements.

Swap - used to move the trias in a particular direction.

• The mesh is then checked and reconstructed and reshaped wherever required.

The final mesh generation after reduced tria elements and refining the mesh are as shown below:

Mid surfaces have been extracted & the given model has successfully meshed.

Learning Outcomes

• Fixing geometric issues such as single cons, cracked surfaces, needle faces etc.
• Taking mid surface by the manual offset method.
• Assigning new PID's to materials.
• Defeaturing Surfaces as per requirements.
• Mesh Generation using best.
• Removal of tria elements.
• Refining the Mesh.

Conclusion

Meshing has been done for given components satisfying the given quality criteria.