HV-3060: Transform and Average Stresses

Learn how to use various averaging methods for elemental stress and transform your results

This exercise uses the bd03bkt.op2 file located in the animation folder as both the model and the results file.
The Averaging method can be selected from the Contour panel.

Figure 1.

Averaging of elemental results at a node refers to the average of all the element corner results passing through that node. If no corner results are available for an element, centroidal results will be used calculate the average. This option allows you to change the results from being element bound to being nodal bound. The various averaging options are Simple, Advanced, and Difference.

Contouring the Model Results

  1. Load the bd03bkt.op2 file, located in the animation folder.
  2. Click the Mask panel button on the Display toolbar to enter the Mask panel.
  3. Verify that the Entities input collector is set to Elements.
  4. Click on Elements, and then select By ID.
  5. Enter the following element IDs into the text box: 108, 16, 12, 107.
    Figure 2.
  6. Click Add.
  7. Click Return.
  8. Click Mask Selected.
  9. Click on the Reverse button.
  10. Click in the graphics area and press F on the keyboard, to fit the model to the active window.
  11. Select the Contour panel from the toolbar .
  12. For Result type, select Stress (t) and vonMises.
  13. Set Layers to Z1.
  14. Activate the Use corner data option.
    Activating this option allows you to view the results at the corners of the elements obtained from the integration/gaussian points.
  15. Verify that the Averaging Method option is set to None.
  16. Verify that Resolved in is set to Analysis System.
  17. Click Apply.
    Figure 3.

    Observe the discontinuities in the contour around the node that is shared by all four elements.

Averaging the Elemental Stresses Using Various Averaging Methods

  1. Change the Averaging Method to Simple.
  2. Click Apply.
    Figure 4.
    Note: The discontinuities around the node no longer exist, and you now are able to view the contour as bands.

    Simple averaging means that tensor and vector components are extracted and the invariants are computed prior to averaging. In this example, the vonMises is computed at the corner of each element for the layer Z1 and then is averaged to the nodes.

  3. Change the Averaging Method to Advanced.
  4. Verify that Resolved In is set to Global System (proj: none).
  5. Click on the Projection Rule button, and turn on Projection (use projected axis as Sxx).
  6. Click OK.
    The Resolved in system automatically changes to Global System (proj: x, y).
    Figure 5.

    Advanced averaging means that tensor (or vector) results are transformed into a consistent system, and then each component is averaged separately to obtain an average tensor (or vector). In this example, the stress components xx, yy, zz, xy, yz, xz are computed at the corners and then averaged to the nodes. From this averaged value, the invariants (like vonMises) are computed. These results are more accurate with advanced averaging.

  7. Click the Averaging Options button to open the Averaging Options dialog.
  8. Activate the Feature angle averaging check box and leave the Feature angle set to 50.
    Figure 6.
  9. Click OK to close the window.
  10. Click Apply to contour the model.
    Figure 7.
  11. Click the Averaging Options button again to open the Averaging Options dialog.
  12. Uncheck the Feature angle averaging option and the click OK.
  13. Activate the Variation option and enter 80 into the percentage box.
  14. Click Apply.
    Figure 8.

    The variation is the relative difference at a node, with respect to all nodes in the selected components.

    The formula is described as follows:

    Figure 9.

  15. Change the Averaging method to Difference.
  16. Click Apply.
    Figure 10.

    This option displays the difference between the maximum and minimum corner results at a node. For tensor/vector components, the corresponding components from each element corner are extracted and the difference is calculated. For invariants, the corresponding invariants are computed from each element corner and then the difference is calculated.