Exercise 2: Check the Minimum Time Step

In this exercise, you will check the minimum time step.

The Time subpanel in the check elems panel calculates element time steps, based on the FEA solver, and allows you to check for time steps that fall below a specified value. In explicit codes such as LS-DYNA, it is sufficient that a single element would have a small time step to drastically reduce the total CPU time of the entire job. For this reason the check is used to identify those elements.

Load the LS-DYNA Profile

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

Only complete this step if you did not complete Load the LS-DYNA Profile in Exercise 1: Create Joints.
  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 pene_dyna.hm file.
The model appears in the graphics area.

Figure 2.

Specify the Template

In this step, you will specify the template in HyperMesh.

The time step associated to an element is related to its geometric characteristic and to its material properties such as density and young modulus. For this reason, a material and a valid template need to be associated to the elements. The time step is dependent upon the user profile, so you may want to load a different profile to see how results may change.
  1. Load a solver template by clicking File > Load > Solver Template from the menu bar.
  2. In the Open dialog, navigate to the LS-DYNA folder and open the dyna.key file.

Check the Time Steps

In this step, you will check the time steps.

  1. Open the Check Elements panel by clicking Mesh > Check > Elements > Check Elements from the menu bar.
  2. Open the time subpanel.
  3. Click check elems.
    The total number of elements failing the check displays in the status bar as seen in Figure 3.

    Figure 3.
  4. Click return.