Exercise 1: Create Joints

In this exercise, you will create a spherical joint and a revolute joint.

You can create joint definitions in the FE Joints panel, which can be accessed from the 1D page. HyperMesh supports the following standard joint types: spherical, revolute, cylindrical, planar, universal, translational, and locking. HyperMesh also supports LS-DYNA’s *CONSTRAINED_JOINT_STIFFNESS_OPTION property to define friction, damping, stop angles, and so on. The LS-DYNA solver interface supports the creation of joints in the FE Joints panel. The PAM-CRASH solver interface currently supports the creation of Joints as rod elements (see HM-4700: Using the PAM-CRASH Interface in HyperMesh).

A spherical joint consists of two coincident nodes. During analysis, the two coincident nodes are forced to remain coincident, but the bodies attached to each coincident node are allowed to rotate freely about the joint location.

Load the LS-DYNA Profile

In this step, you will load the LS-DYNA profile in HyperMesh.

  1. Start HyperMesh Desktop.
  2. In the User Profile dialog, set the user profile to LsDyna.
  3. Select the Keyword971_R10.1 template from the drop down list.
  4. Select OK to close the User Profile dialog.


    Figure 1.

Retrieve and View the Model File

In this step, you will open the model file and view it in HyperMesh.

  1. Open a model file by completing one of the following options:
    • Click File > Open > Model from the menu bar.
    • Click on the Standard toolbar.
  2. In the Open Model dialog, open the joints.hm file.
The model appears in the graphics area.


Figure 2.

Activate Coincident Node Picking

In this step, you will activate coincident picking within the Graphics panel.

According to the LS-DYNA specification, a joint needs to reference a pair of coincident nodes. The creation of this element requires the selection of coincident nodes. To select coincident nodes, activate the coincident node picking option in HyperMesh, and then select a coincident node. HyperMesh will present you with a selection circle identifying the coincident node ID.
  1. Open the Graphics panel by clicking Preferences > Graphics from the menu bar.
  2. Select the coincident picking checkbox.
  3. Click return.

Change the Display

In this step, you will change the display of the model in the graphics window by disabling components in the Model Browser.

  1. In the Model Browser, expand the Components folder to display the contents.
  2. Click next to each component except blue torus, orange torus, and New Joint to disable the display of those elements.


    Figure 3.
The blue torus, orange torus, and New Joint are the only components displayed in the graphics window as seen in Figure 4.


Figure 4.

Create a Spherical Joint

In this step, you will create a spherical joint using the Joints panel.

  1. Open the Joints panel by completing one of the following options:
    • Click Mesh > Create > 1D Elements > Joints from the menu bar.
    • In the Solver Browser, right-click and select Create > *CONSTRAINED > *CONSTRAINED_JOINT_SPHERICAL > *CONSTRAINED_JOINT_SPHERICAL from the context menu.
  2. Set the joint type to spherical.
  3. Use the node 1 selector to select a node in the center of both tori as indicated in Figure 5.
    The coincident node picking mechanism appears and displays two nodes, node 598 and node 1.


    Figure 5.
  4. Select the node labeled 598.


    Figure 6.
  5. Using the node 2 slector, select the node created in step 4.
    The coincident node picking mechanism appears and displays two nodes, node 598 and node 1.
  6. Select the node labeled 1.


    Figure 7.
  7. From the the Joints panel, click create.
    HyperMesh generates the spherical joint element seen in Figure 8.


    Figure 8.
  8. Click return to exit the panel.

Change the Display

In this step, you will change the display of the model using the component folder of the Model Browser.

In the Model Browser, Component folder, turn off the display of all of the components, except Bearing, Shaft, Bearing Rigids, Shaft Rigids, and New Joint.


Figure 9.
Figure 10.
The Bearing, Shaft, Bearing Rigids, Shaft Rigids, and New Joint are the only components displayed in the graphics window as seen in Figure 10.

Create a Revolute Joint

In this step, you will create a revolute joint using the Joints panel.

A revolute joint consists of four nodes, two sets of two coincident nodes. During analysis, all four of the revolute joint’s nodes remain at the same location with respect to each other. The bodies attached to the nodes are free to rotate about the axis that lies along the length of the revolute joint.
  1. Open the Joints panel by completing one of the following options:
    • Click Mesh > Create > 1D Elements > Joints from the menu bar.
    • In the Solver Browser, right-click and select Create > *CONSTRAINED > *CONSTRAINED_JOINT_REVOLUTE > *CONSTRAINED_JOINT_REVOLUTE from the context menu.
  2. Zoom in on one end of the shaft assembly as indicated in Figure 11.


    Figure 11.
  3. Set the joint type to revolute.
  4. Using the node 1 selector, select a node at the center of one of the rigid link elements.
    The coincident node picking mechanism appears.


    Figure 12.
  5. Select node 6788, which is attached to the blue rigid link element.
    Tip: Drag your cursor over a node in the coincident node picking mechanism to highlight the attached element.
  6. Using the node 2 selector, select the node that was created in step 5.
  7. Select node 6899, which is attached to the orange rigid link element.
  8. Using the node 3 selector, select a node at the center of the opposing pair of blue and orange rigid link elements.
    The coincident node picking mechanism appears.


    Figure 13.
  9. Select node 6787, which is attached to the blue rigid link element.
  10. Using the node 4 selector, select the node that was created in step 9.
  11. Select node 6898, which is attached to the orange rigid link element.
  12. Click create.


    Figure 14.
  13. Click return.