Connecting nodes with spider elements

Estimated time to complete: 15–25 minutes

In this tutorial, you will create spider elements and then apply loads to them.

1: Setup

  1. On your desktop or the appropriate network drive, create a folder named spider.

  2. Click the link below:

    Download the part

  3. Extract the part file to your spider folder.

  4. Start Simcenter 3D or NX.

  5. Open spider_sim1.sim.

2: Reset dialog box memory

The options you select in dialog boxes are preserved for the next time you open the same dialog box within a given session. Restore the default settings to ensure that the dialog boxes are in the expected initial state for each step of the activity.

File

Preferences→User Interface

  • Options

  •   Reset Dialog Memory

  • OK

     
3: Display the FEM file

Make the FEM file both the displayed part and work part.

  Simulation Navigator

  •  

  •   spider_fem1

      Make Displayed Part

4: Create a 2D seed mesh

Create a 2D seed mesh that will force the 3D mesh to follow a paver mesh around the holes in the part.

  2D Mesh (Home tab→Mesh group)

  •  

  • Type

    CQUAD4

  • Meshing Method

    Paver

  • Element Size

    6 mm

  •  

  •   Export Mesh to Solver

  • OK

     

     

5: Create a 3D mesh

  3D Tetrahedral (Mesh group)

  •   the part

  • Type

    CTETRA(10)

  • Element Size

    6 mm

  •  

     

  •   New Collector (Mesh Collector)

  •   Create Physical (Solid Property)

  •   Choose material (Material)

  • Materials

    Aluminum_2014

  • OK

     Material List, PSOLID, and Mesh Collector dialog boxes

  •   Automatic Creation

  • Mesh Collector

    Solid(1)

  • OK

     3D Tetrahedral Mesh dialog box

 

6: Create point-to-edge spider elements

You will create a spider element in each of the holes in the model to provide a place to apply loads. For the first three holes, you will use the point-to-edge technique.

1D Connection (Connections group)

  • Type

    Point to Edge

  •  

     

  •  

  •   (Select Point)

  • Select the arc center as the source.

     

  •  

     

  •   (Select Edge)

  •  

  • Type

    RBE2

  •  

     

  •   Connect Mid-Nodes

  • Apply

     1D Connection dialog box

  • Repeat these steps for the next two holes, moving clockwise from the upper-left hole. For the subsequent holes, however, select the Connect Mid-Nodes check box.

  •  

    Note:

    The upper left hole has fewer legs in its spider element because it was created without the mid-nodes option, which generates connections at the mid-node of each element.

  • Cancel

     1D Connection dialog box

7: Create a node-to-node spider element

You will create the last spider element using a different technique, which can be helpful when creating a spider element in an irregularly shaped hole.

Nodes and Elements

 Node Create (Nodes group)

  •  

  • Specify Point

    Arc/Ellipse/Sphere Center

  •  

  • OK

     

  •  

 

Home

 1D Connection (Connections group)

  • Type

    Node to Node

  •  

    Select the node that you created in the previous step.

  •  

  •   Node (Select Node)

  •  

  •  

     

  •   Node (Select Node)

  • Method (Top Border bar)

    Related Nodes

  • Type Filter (Top Border bar)

    Polygon Edge

  • Select the edge of the hole.

  •  

  • All nodes along that edge are selected automatically.

  • Type

    RBE2

  • OK

     

  • In the next step, you will modify this element.

8: Modify element connectivity

When you use the node-to-node technique to create a spider element, you cannot specify whether or not to include legs to the mid-nodes; they are created automatically. However, you can add or remove legs for any 1D connection as needed.

Nodes and Elements

  Connectivity (Elements group)

  •  

  • Single Element

  •  

  • Type

    Modify Leg Nodes

  • Press Shift and select some of the mid-nodes.

         

  • To add a leg to a node, select the node without pressing the Shift key.

  • OK

     

  •  

9: Make the Simulation file the displayed and work part

Make the Simulation file the displayed and work part so you can apply boundary conditions.

  Simulation Navigator

  •  

  •   spider_sim1

  •   Make Displayed Part

10: Constrain the groove

Constrain the groove on the underside of the part.

 Fixed Translation Constraint (Home tab→Loads and Conditions group→ Constraint Type list)

  • Type Filter (Top Border bar)

    Polygon Face

  •  

  • OK

     

  •  

11: Create a group of spider elements

You will use a group to quickly apply the loads.

  Simulation Navigator

  •   Groups

  •   New Group

  • Type Filter (Top Border bar)

    Node

  • Select the center node of each spider element.

           

  •  

    Name

    Spider Nodes

  • OK

12: Apply a load to the group

Use the new group to apply loads to the spider elements.

  Force  (Loads and Conditions group→  Load Type list)

  •  

     

  •   Group Reference

  • Name

    Spider Nodes

  •  

     

  • Force

    100 N

  •  

     

  • Specify Vector

      –XC Axis

  •  

     

  • Method

    Total per Object

  • OK

     

 

At this point you can check the model, solve it, and display the results.

 Save

File

  • Close→All Parts