Project - 2 - Meshing on the suspension Assembly

AIM: To perform Meshing on the suspension assembly using ANSA.

Objective:

• To perform the pre-requisites such as, checking for the given CAD goemetry errors & perform the topology clean up.
• To Generate a 2D mesh with the tria elements for the tyre & rim components.(Because, the given quality criteria is same for both tyre & rim).
• To generate the 2D mesh for some components of which the thicknesses are less than 5 mm.
• To define the volume & generate a 3D mesh for all components by using tetra elements with the help of already generated 2D mesh with tria elements.
• To deploy the connections with RBE2 elements(As the connection data is not given).
• To reflect the entire meshed part. Inorder to get a whole rear wheel assembly.

 

Procedure:

Step 1: Pre-requisites:

Initially, the given rear wheel assembly is imported in to the ANSA software tool. After importing, it appears in the graphical display as shown in fig 3.1.

                 

                                                                    fig 3.1

Then the check for geometrical errors is done. This is done by using "Checks" option from tool panel. In that, the Geometry option is choosed. As shown in fig 3.2.

                

                                                               fig 3.2

Then a dialog box appears as shown in fig 3.3. In which the aspects to be verified on the given geometry is enabled.

               

                                                               fig 3.3

After clicking "OK", the errors related to the geometry are shown in a dialog box. As shown in fig 3.4.

              

                                                              fig 3.4

Many of these errors are fixed automatically, by using "Fix" option. And some of the errors are fixed manually. After eliminating all errors with respect to the geometry, again the check is runned. Which shows an error free geometry, as shown in fig 3.5. 

              

                                                                 fig 3.5

Topology clean up:

Initially, the rim is taken to perform the tasks. So other than the rim, all parts are hided. After enabling only the rim, it appears in the graphical display as shown in fig 3.6.

                                

                                                                  fig 3.6

Then the distance between the cons are measured, Which seems to be closer. By using "Measure" option from utilities panel. The distance is mesured between two cons, as shown in fig 3.7. Inorder to get rid from minimum element length errors during meshing.

             

                                                             fig 3.7

Similarly, the distance is measured at so many regions(Where the cons appears close to each other). As shown in fig 3.8.

             

                                                                  fig 3.8

In the regions with the distance between the two cons less than the minimum element length, a curve is generated at the middle. This is done by using "Middle" option from curves in topo module, As shown in fig 3.9.

                                           

                                                                   fig 3.9

After generating a curve at the middle of two cons, it appears as shown in fig 3.10.

              

                                                                fig 3.10

Then the created curve is projected on to the face. This is done by using an option named "Project" from cons in topo module. As shown in fig 3.11.

                                             

                                                                  fig 3.11

After projecting, the newly created con at the middle appears as shown in fig 3.12.

                             

                                                                  fig 3.12

The cons at the adjacent to the middle con is toggled. Which is represented as a orange coloured line as shown in fig 3.13.

                             

                                                                       fig 3.13

Similarly, the geometry clean up is done(Wherever necesscary). After geometry clean up, the rim appears as shown in fig 3.14.

               

                                                                 fig 3.14

 

Step 2: Meshing of rim:

After finishing the geometry clean up, the 2D mesh with tria elements is generated. So, the mesh parameters are assigned as shown in fig 3.15.

Note: The element type should be switched to "Tria".(As mentioned in the question).

                

                                                              fig 3.15

Then the quality criteria is assigned for the tyre & rim(As mentioned in the question). As shown in fig 3.16. By clicking on "Apply", the quality criteria is assigned.

              

                                                                          fig 3.16

Then the distance between two nodes is assigned for both perimeters & macros as the target element length(i.e., 6.5mm). As shown in fig 4.17. Inorder to have proper mesh flow & eliminating the chances of element failure with respect to the minimum & maximum element length.

              

                                                                fig 3.17

After assigning the distance between the nodes, It is verified by using "Measure" option from utilities panel. It shows the distance between two nodes close to the assigned target element length. As shown in fig 3.18.

                                

                                                                 fig 3.18

Then the 2D mesh is generated by using any algorithm. And the algorithm used to generate a 2D mesh in this project is "Spot mesh" from mesh generation in mesh module. As shown in fig 3.19.

                                               

                                                                   fig 3.19

And the faces are selected and mesh is generated. Initially, there will be some elements failing for the quality criteria. As shown in fig 3.20.

                          

                                                                 fig 3.20

Those errors can be eleminated by using "Re-construct" & "Smooth" option from shell mesh in mesh module. Similarly, all macros of rim is meshed with 2D tria elements. After meshing, it appears as shown in fig 3.21. 

                

                                                                       fig 3.21

 

Step 3: Volume mesh of rim:

Then the volume mesh is generated from the already generated 2D mesh. To generate the 3D mesh, the volume is to be defined. So, the option named "Define---> Manual" from volumes in volume mesh module is used. As shown in fig 4.22.

                                              

                                                                    fig 3.22

After selecting manual definition of volume, a dialog box appears as shown in fig 3.23. In which the auto option is selected and the macros are selected, To define the volume.

            

                                                              fig 3.23

After defining the volume, the quality criteria for generating 3D mesh(Tetra elements)is assigned. This is done by enabling the quality criteria & entered the required quality parameters. As shown in fig 3.24.

             

                                                              fig 3.24

Then the method to generate the 3D tetra mesh is choosed. The metod used in this project is "Tetra FEM" from unstructured mesh in volume mesh module. As shown in fig 3.25. 

                                               

                                                             fig 3.25

Note: Any method can be used for generating 3D tetra mesh(Not only Tetra FEM). All methods are same but, the algoithms to generate the mesh differs.

Then the volume is selected. As shown in fig 3.26. Which represents the volume is defined as ( volume, Unmeshed:1).

            

                                                              fig 3.26

By middle clicking the mouse, the 3D volume tetra mesh is generated as shown in fig 3.27. Which represents an element is failng for tet collapse.

            

                                                                   fig 3.27

To eleminate the element failing with tet collapse, "Fix quality" option from improve in volume mesh is used. As shown in fig 3.28. The process is: Improve---> Fix quality---> Visible.

                                                 

                                                                    fig 3.28

After eleminating errors with respect to 3D mesh, the rim appears as shown in fig 3.29.

           

                                                             fig 3.29

Inorder to have a clarity wheteher the tetra elements are creted or not, the bounds option is enabled & some tetra elements are hided. As shown in fig 3.30. WHich shows the tetra elements are formed.

                                        

                                                                fig 3.30

 

Step 4: Topology clean up for tyre:

Then the tyre is enabled. After enabling the tyre, it appears in the graphical display as shown in fig 3.31.

            

                                                                fig 3.31

For the regions where the distance between two cons is less, a middle curve is created. As shown in fig 3.32.

                        

                                                                fig 3.32

Similarly, The topology clean up is done for tyre. After performing topology clean up for tyre, it appears as shown in fig 3.33.

               

                                                                   fig 3.33

 

Step 5: Generating 2D tria mesh & 3D tetra mesh for tyre:

The mesh parameters & quality criteia for both tyre & rim is same. So, the 2D tria mesh is generated for all macros of tyre. As shown in fig 3.34.  

            

                                                                 fig 3.34

Then the volume is defined. After defining the volume, the tetra mesh is generated. As shown in fig 3.35

            

                                                                     fig 3.35

As similar to that of rim to view the formed tetra elements, the bounds option is enabled. Which represents the formed tetra elements with red coloured edges. As shown in fig 3.36.

                    

                                                               fig 3.36

 

Step 6: Extracting mid-surface for the parts with thickness less than 5mm & generating 2D mesh:

In this suspension assembly component, there are two parts with the thickness less than 5 mm. As shown in fig 3.37.  

                         

                                                                   fig 3.37

Those two parts are: One is disc shaped & the other one is a bracket. As shown in fig 3.38.

           

                                                                 fig 3.38

Then the mid-surface is extracted for the two parts by using "Offset" option from faces in topo module. As shown in fig 3.39.

                                               

                                                                     fig 3.39

After extracting the mid-surface for those parts, the extracted mid-surface for those parts appears as shown in fig 3.40.

              

                                                                  fig 3.40

Then the 2D mesh is generated with the mixed type elements. So, the mesh parameters & quality criteria mentioned for shell meshing is entered. As shown in fig 3.41 & 3.42.

Note: The lock view should be enabled by hiding all parts except these two parts. Because, the mesh parameters & quality criteria is different from the tyre & rim.

             

                                                                fig 3.41

             

                                                                fig 3.42

After assigning the mesh parameters & quality criteria, by using "spot mesh" from mesh generation in mesh module the 2D mesh with the mixed(Quads+Trias) elements is generated. After generating the mesh, those parts appears as shown in fig 3.43. And thickness is assigned by using "Draw shell as solid" option from presentation parameters in quality criteria panel 

             

                                                           fig 3.43

 

Step 7: Topology clean up & 2D mesh generation for the parts in suspension assembly:

The suspension assembly consisits of several parts in it. Some of them are brake calliper, steering rod, spring, Disc etc. So, The process will be done part by part. Initially, the brake calliper is meshed. Prior to that, the required topology clean up is done on it. After performing the clean up, the brake calliper appears as shown in fig 3.44. 

Note: The lock view is enabled. Because, the mesh parameters & quality criteria is different for the suspension assembly

             

                                                            fig 3.44

Then the mesh parameters are entered, As shown in fig 3.45.

             

                                                                fig 3.45

Then the quality criteria is assigned, As shown in fig 3.46.

             

                                                               fig 3.46

Then all macros of brake calliper is meshed with 2D tria elements. After generating the 2D mesh, it appears as shown in fig 3.47.

 

                 

                                                                 fig 3.47

Then remaining parts such as shown in fig 3.48, the topology clean up is done.

                                    

                                                                 fig 3.48

After 2D meshing with tria elements, it appears as shown in fig 3.49.

                                    

                                                                  fig 3.49

Similarly for all parts in the suspension assembly, the topology clean up and 2D mesh is generated.

 

Step 8: Modeling the spring element:

The spring element alone is enabled in the graphical display. As shown in fig 3.50.

                                    

                                                                     fig 3.50

Then a curve is created at the middle, by using middle curve option from topo module. As shown in fig 3.51. 

                          

                                                                  fig 3.51

After creating the curve, to define the orientation of 1D elements a COG point created. This is done by using an option named "On COG" from points in mesh module. As shown in fig 3.52. After creating the curves, those curves are connected to form a single curve by using multi connect option from curves in topo module.

             

                                                               fig 3.52

The created COG point appears as a blue coloured square at the middle as shown in fig 3.53.

                                               

                                                                     fig 3.53

Then to represent the spring, the 1D element named "CBAR" in elements from NASTRAN deck is used. And by selecting the COG point, a dialog box appears as shown in fig 4.54. In which the "Orientation is choosed with respect to node(s)" is enabled. And picking is done box selection of curve. So, "Curve (box)" is switched. As shown in fig 3.54.

             

                                                                 fig 3.54

Then by middle clicking on mouse, a dialog box appears as shown in fig 3.55. In which the 1D element length to be created is specified.

                                 

                                                            fig 3.55

After specifying the element length, a dialog box appears in which a new property named "PBAR" is created. And to assign the specifications of the property, In the area section(A), as shown in fig 3.56 by pressing Shift+? a new dialog box appears in which the radius of spring is specified(i.e., 5 mm). By entering the radius value, the area of the spring will be calculated automatically.

     

                                                           fig 3.56

By clicking"Ok", a spring with the 1D CBAR elements will be created. As shown in fig 3.57.

                             

                                                                  fig 3.57

Then to represent these 1D elements as 3D solid element, An option named "Line elements cross section---> As solids" is enabled from presentaion parameters. As shownin fig 3.58.

            

                                                                    fig 3.58

After enabling it, the spring element appears as shown in fig 3.59.

                               

                                                                fig 3.59

 

Step 9: Generating 3D(volume) mesh for the parts in suspension assembly:

After meshing all macros of suspension assembly with 2D elements, it appears as shown in fig 3.60.

           

                                                                   fig 3.60

Then the volumes are defined seperately for different PID's. The process of defining a volume is: Volume mesh module---> Auto detect, As shown in fig 3.61.

                                            

                                                                     fig 3.61

Then a dialog box appears as shown in fig 3.62. In which the auto detection of volumes is switched to "Visible". Which means the detecting the volumes is applicable only to the parts which are visibled on graphical display.

                                             

                                                                    fig 3.62

Then the volumes will be created automatically for each PID's. Then the volume mesh is generated for all PID's in suspensiom assembly part by any method. And to know whether the volume mesh is generated for all PID's or not, The list of all volumes is opened. As shown in fig 3.63.

             

                                                                  fig 3.63

Some of the elements in any one of the parts are hided to check the tetra elements, which appears as shown in fig 3.64.

                                        

                                                                 fig 4.64

After generating the 3D tetra mesh, the entire suspension assembly appears as shown in fig 3.65.

           

                                                                     fig 3.65

 

Step 10: Deploying connections:

As the connection data is not mentioned, the connections are deployed by using rigids(RBE2) element. Which is available in elements from NASTRAN deck, as shown in fig 3.66.

                                                   

                                                                    fig 3.66

Then the slave nodes are selected. After selecting the slave nodes, a dialog box appears as shown in fig 3.67. Which depicts the ground node ID, Degrees of freedom(CM). By clicking on finish, a connection is deployed between the two parts by RBE2 elements.

                                            

                                                                 fig 3.67

The deployed RBE2 connection appears as shown in fig 3.68. Similarly, The RBE2 element is used to deploy the connections wherever needed.

                                            

                                                                fig 3.68

After depliying the connections at all necesscary points, the whole rear wheel suspension assembly appears as shown in fig 3.69.

              

                                                                 fig 3.69

 

Step 11: Reflecting the meshed rear wheel assembly:

Before reflecting, the parts with the 2D mesh are released. Because, the faces are not refleted. So, This can be done by using "Release" option from elements in mesh module. As shown in fig 3.70.

Note: Disconnect from neighbors should be enabled. If it is not enabled, then whole mesh in connection will be released from the geometry.

                                           

                                                                  fig 3.70

Then the faces option is disabled, Which is highlighted as shown in fig 3.71.

                                              

                                                                    fig 3.71

Then to reflect, an option named "Transform" from utilities panel is used. And "copy" comand is selected. As shown in fig 3.72.

                                           

                                                               fig 3.72

After selecting "copy", a dialog box appears as shown in fig 3.73. In which the mode of performing is to be selected. In that, the mirror with refernce to 3 points plane is selected.

                                 

                                                                 fig 3.73

Then a dialog box appears as shown in fig 3.74. In which the three points which acts as a refernce is selected as X1, X2, X3. There by clicking "Apply" & "Finish", the meshed rear wheel assembly will be reflected.

                                                                  fig 3.74

Finally, After reflecting the entire rear whwwl assembly appears as shown in fig 3.75

             

                                                                     fig 3.75

 

Conclusion:

• Done the pre-requisites such as, checking for the given CAD goemetry errors & perform the topology clean up.
• Generated a 2D mesh with the tria elements for the tyre & rim components.
• Generated the 2D mesh for some components of which the thicknesses are less than 5 mm.
• Defined the volume & generate a 3D mesh for all components by using tetra elements with the help of already generated 2D mesh with tria elements.
• Deployed the connections with RBE2 elements(As the connection data is not given).
• Finally, Reflected the entire meshed part. Inorder to get a whole rear wheel assembly.

 

Learning outcomes:

By performing this project, the following concepts can be learned:

• Importance of geometry clean up(i.e., Errors with respect to the geometry).
• Meshing the geometry with both ortho tria & tria elements.
• Meshing the parts with thickness less than 5mm.
• Reason for representing the spring elements as 1D CBAR elements.
• Performing volume tetra mesh by using the already generated 2D mesh.
• Deploying the connections.
• Using reflection by using "symmetry" option. Which reduced the time for modelling of any component.

 

 

Drive link for the model:https://drive.google.com/file/d/12suyFuzC-WBHQNA_9yLhjOjktpMh4xg4/view?usp=sharing