Week - 7

Aim:

The main objective is to create a Mid-surface using Skin, Casting, and Offset and using the Batch Mesh using the given Quality Criteria and Meshing Parameters.

S. No.	Quality Criteria	Value
1	Target/Average length	3
2	Minimum Length	1
3	Maximum Length	5
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

Methodology:

The methodology is to create a particular process to attain a proper mesh flow.

1. Making Geometry Clean-up.
2. Creating Mid-surface using Offset, Skin, and Casting.
3. Generating the normal mesh and Batch Mesh.
4. Comparing each method.

Procedure:

1. Opening the File:

• The file is downloaded initially. To open the file, follow the steps.
  Open ANSA >> Give Command Arguments >> OK >> Click Ctrl +O (for opening the file) >> Select the File>> Click Ok.
• On the Whole to describe the Opening of a file, click on the ANSA app, and wait for the launcher dialog box to appear.
• Once it appears, the dialog box contains the information called Additional ANSA command arguments are seen there will be an input box just below it.
• The argument has to be changed to “-performance_mode 3” (This means the performance of the app and it has Slower drawing and yet better quality.) then click ok to continue.
• The ANSA is now opened and then you can either open the file by using file option and open or Ctrl + O option.

2. Checking the Geometry:

• This process is just used to check the topology of the model. In order to check the Topology follow the process as Tools>> Checks >> Geometry>> Execute.
• Once executed, it might show a green bar stating there are no errors in the geometry or it may show the dialog box showing the errors present in it.
• These errors can be fixed either by going on with them individually or once Right-clicked on the mouse an additional list pops- up.
• Fix option will be present in that pop-up when it is clicked the errors which can be fixed are executed and it might contain only a few errors which should be fixed manually and if no errors are present then it will show the green bar stating executed.
• The process is called geometric clean- up. It can be done either completely or part-wise of the parent geometry.

3. Creating the Mid-surface:

The Mid-surface is created by using different methods such as Automatic Mid-Surfacing like Skin, Casting, and manual Mid-surfacing methods like Offset.

• Using Skin:

• The Skin Method is an automatic way of creating the Mid-surface in which two faces are automatically selected and thickness is also represented in a different color.
• In Topo Deck, Faces module >> Mid Surfacing >> Skin >> Select the Part >> Check the Colours and Select >> Click Offset.
• The Mid Surface is generated, similar to that of the parent geometry.

• Using Casting:

• The Casting option is used to create the Mid-surface. Some basic pre-requisites are required to generate a mid- surface.
• In Topo Deck, Faces module >> Mid Surfacing >> Casting>> Give the Minimum Thickness, Target Element Length >> Click OK.
• The mid surface is created with the mesh FE generated.

• Using Offset:

• The Offset is the Manual Mid surfacing method in which the face of the model is selected and the value is given which is half of the parent Geometry thickness.
• In Topo Deck, Faces Module >> Click Offset >> Faces>> Select the Face >> Give the Offset Value >> Click OK.
• The Mid Surface is created.

4. Generating a Mesh:

• The mesh can be created in two ways Automatic Mesh or Manual Mesh. Automatic Mesh is created as the batch mesh and Manual mesh is created as spot, best, etc.
• The Batch Mesh can be selected from Tools manager or by clicking Ctrl + B.
• Tools Manager >> Batch Mesh >> New >> Meshing Scenario >> Select the Mid surface by double clicking >> Select PID >> Click Ok >> Give the Meshing Parameters and Quality Criteria >> Click Run.

Terms used:

1. Skin:

The function turns the solid description of a thin part into a thin shell description by isolating the outer or inner skin of the solid description.

2. Casting:

This completely automatic function is used to create FE shell elements that represent the middle skin of a solid description.

3. Difference between Skin and Casting:

The Skin and Casting are Automatic Mid Surfacing processes. The main difference is that Skin creates just the Mid-surface which has the same thickness over the area and the Casting creates the Mid-surface along with the mesh automatically. Casting is generally done for Plastic materials which have different thickness. And skin is used for the same or uniform thickness.

4. Batch Mesh:

Batch Mesh is an automatic type of mesh that creates the mesh automatically for the selected part with the given Quality Criteria and Meshing Parameters automatically.

5. How is it different from normal mesh?

The normal mesh is created after the geometric clean-up is done that is when the cons are not meeting the quality criteria and by checking the minimum length error. The Batch Mesh, However, cleans up automatically and produces the mesh.

Results:

The Mesh is created by using Different Methods as the Skin, Casting, and Batch Mesh.

Comparing:

• The Different methods show different types of mesh flows and different mid-surface structures.
• The Following shows different types of mesh flow and Structure of the surface.
• The mid-surface is created by using Skin, casting and Offset methods
• The Skin and Offset create the proper mid-surface and casting surface which is created does not have proper surface.
• The Batch mesh which is created does not have a proper mesh flow comparatively to the normal mesh which creates the proper mesh flow.
• The Casting mesh has many Off elements and the mesh had to be cleared.

The Top left image shows the Batch mesh using Skin, Top Right shows the Casting method, and the Lower image shows the Offset method and normal mesh.

Learning Outcomes:

There are many things that are learned and basically, researched about the different methods of Mid Surface creation and Mesh generation. The following are the learning outcomes

1. Generation of Mid Surface using Skin, Casting, and Offset
2. Using of Batch Mesh.
3. Checking the mesh flow.

Google Drive Link: Sheet Metal Meshing Using Different Methods