Project 2

Meshing of Sub System Level Rear Suspension Model to quality criteria

Objective

• Follow the geometrical cleanup.
• Setting up properties i.e. PID setup, material ID and the meshing parameters
• Extracting the middle surface from a component.
• Creating the surface meshing and converting it to volume mesh.
• Meshing of given component according to quality criteria.
• Creating required connection from connection data

Procedure

• Click on ANSA icon. It will ask you to choose the working directory and layout to work.
• You can use the performance mode for graphical issue.
• Type (-performance_mode3) to get good results in below window.

• Select ANSA and hit OK.
• Click on Import geometry. It might be .step, igs, or in another format.

• It will appper as a shaded view in Entity mode. On left side it will shows the database.
• Database include some important tabs like properties and material.
• You have to make the component fine to get actual view of cad geometry, and follow the topology.

• When you fine all the areas you will get the exact idea about how the surface looks. As shown below.
• Now we have to measure the surface thickness to verify the component have uniform thickness or varying thickness.
• Here the thickness of component is varying at different places. So, we have to set the PID according to the thickness of each different thickness section.

• Now we are remaining with only surfaces which we are going to use for meshing.
• All analysis depends on a good meshing so we are going to mesh individual components.

1. Geomertry Cleanup

• Here we have separated the different surfaces according to the thickness of the component with different PID as shown in the picture below.

• Now click on the inner extract component. We have to check the component for the proper surface, which is free from any errors. Such as middle face, cracks, single, double, triple cons before taking mid surface.
• For checking the geometry, we have to go to the geometry checks manager to get error free surface.

• Removal of this errors in geometry lead to get the good and clear middle surface.
• We can remove errors individually or all together, it depends on the complexity of error.
• Errors can be removed manually or automatically. But manually fixing will give the better results.

After removal of all the errors we will get a clear surface. Now we can go for the middle surface

• Set the property id for extracted mid surface. Property may define the thickness of the shell elements.

1. Setting up parameters and quality criteria

• Set the required mesh size, type of mesh and order of meshing required,according to customer requirements and accuracy required.

Eg. Target Element Size= 1mm as shown in picture.

• Now click on edit criteria. This is where we have to specify the criteria for the Quality index of meshing.
• Set all the quality criteria and save the details as a file.

• These are the criteria on which our meshing gets checked on quality of meshing.

E.g. Min/ Max Size of element, Aspect ratio, Warpage, Min/Max Quad angle, Skewness etc.

1. Meshing

• After geometric cleanup and setting the conditions now we are going for meshing.
• We have to finalize the target mesh size and set the perimeter length. Setting of the perimeter length for meshing divides the surfaces into the imaginarily small parts for required meshing.
• Select the surface as displayed surface. Choose element size as per requirement. Here it is
• Use mesh type as Mixed. And hit the mesh button on screen.
• Adjust the nodes according to requirements. Make sure the mesh flow is good. Adjust each area of meshing with care to get a quality mesh. Hit middle mouse button to exit the mesh.

• Mesh flow near cutouts and at edge will specify mesh quality. Now meshing is done. It’s time to check the quality of the mesh.

1. Quality Check

• Click on quality index. It will show the no. of elements failing in quality criteria which we have specified previously. The quality of elements are only seen in the hidden mode. Change the mode to hidden and check the quality of elements.

• So the quality index will show the failing elements or worst elements in the meshing. We have to avoid these elements during meshing. We can overcome these elements by remeshing certain areas again which is a good way to do it.
• Click on F11 and select the elements. Select the element from the outer edge to reconstruct the surface.

• Make a square to remeshing. It will easy to reconstruct targeted area. This is way to get remesh all the surface again and again. Repeating this procedure you will refine mesh.
• Now again we can check for the quality criteria. In quality index we can use the tools like place node, node optimize, element optimize, split option, paste, split quad, combine tria etc
• These tools also help to get rid off from bad mesh.
• Place Node use to place a node at a required position. We can use element optimize to adjust the element as per meshing thresholds specified earlier. These options will adjust the element at minor level..
• Split and combine tria are also used for removing tria from mesh or adding together to form a quad element.
• Apart from these entire tools smooth tool is used for very minor adjustments in the elements to complete quality criteria.
• After doing all this you will get a quality mesh which will pass all the quality criteria. In industry point of view the tolerance is given for quality criteria’s it may be in 5% to 10%.

1. Creating Volume

• Now we are going to define the volume as we converting 2D mesh to 3D.
• Click on upper right corner to change to volume mesh.
• Go to list in volume tab, where you get list of volume. Right now no volume is defined here.
• First you have to define the volume manually.
• Before that we have to check the geometry and pre volume meshing checks in checks manger. This check ensure there is no any problem like leak in model or any penetration.
• Now define the volume by any method i.e Manual or Auto
• If you click on auto then it will automatically creates the volume.
• Now the status of volume is also shown in the list as given below
• Now we have to click each volume and we have to remesh the volume according to the required algorithm in the ANSA.
• As we are doing this meshing using Tetra FEM.

Identify the connections required

• We have to make sure which type of connection we have to deploy as per given CAD data.
• Sometimes the connection data is provided.
• There are different types of connections are possible in any assembly, such as spot weld, seam weld,

Bolt connections etc

Creating a RBE2 Connection

• In RBE 2 two different method included namely Many nodes and Two Nodes. Choose the suitable conditions according to the requirement.
• Selection of node is have different methods such as feature angle selection, loop selection, path selection etc.
• Apart from node we can select the elements for choosing different nodes.
• Select the required node and hit the middle mouse button to accept.

Creating a RBE2 Cluster Connection

• The RBE 2 cluster is mainly created using two different parts together.
• The nodes from two different parts are joined together to form a rigid connection.
• The RBE2 consist of the two types of nodes namely slave node and master node.
• The master node gets created at the COG of all the nodes.
• The DOF can be restricted during the entity creation.

Creating a Bolt Connection automatically

• The bolt connection can be created manually or automatically.
• In manual method we have to create the two different RBE2 link (as representation of bolt and nut) and join it by another RBE2 (Bolt Stem).
• In automatic method we have to only specify a center point and the ANSA will create the bolt itself.
• For creating a point, we have to create a 3D point in topo mode.
• This point is converted to bolt directly using the connection manager.
• We have to realize the bolt by providing the details regarding the joining point, search distance, and type of bolt required.
• Here in automatic bolt realization the each RBE2 work as a separated connection and the bolt stem generation is also automatic. This will save the time during connections.

Similarly we have to do the meshing for all the parts and follow the procedure to get good meshing.

Now unhide all the meshing to see the whole component together.

Conclusion:

1. Topology is very important in plastic components. We require to extract middle surface using manual method. Using tools like offset, Middle, curve middle etc.
2. Elements violating threshold are zero. So the quality of mesh is good. And we can decide good mesh quality based on the mesh flow as well. So below figure shows the good mesh flow. So we can conclude the meshing is of good quality.
3. We have to use ortho tria for curved surfaces as the surface we require should be smooth. The ortho tria have the better convergence than regular tria The regular tria can be used for plane surfaces.
4. During definition of volume the geometry should be free from leaks. Any error in geometry will not form the closed volume.
5. Elements violating threshold are zero. So the quality of mesh is good. And we can decide good mesh quality based on the mesh flow as well. So below figure shows the good mesh flow. So we can conclude the meshing is of good quality.
6. Connectors are required to connect to different components, as in actual work environment.
7. If we want to delete the connector we should delete it with its FE files or it may create some issue.
8. There are various types of connectors are available according to conditions given in CAD model.
9. Connectors should be chosen wisely to get good results.
10. Connector during creation can spoil the mesh flow, so we have to pay attention to the mesh flow after connector creation.