Stress-Life (S-N) Approach

In this tutorial you will:
  • Import a model to HyperLife
  • Select the SN module and define its required parameters
  • Assign materials
  • Assign load histories for scaling the stresses from FEA subcases
  • Evaluate and view results

Prior to running through this tutorial, copy Models-h3d.zip from <HyperWorks_installation_directory>\tutorials\hl to a local directory. Extract Shaft.h3d, load1.csv, and load2.csv from Models-h3d.zip..

Import the Model

  1. From the Home tools, Files tool group, click the Open Model tool.


    Figure 1.
  2. From the Load model and result dialog, browse and select Shaft.h3d for the model file.
    The Load result field is automatically populated. For this tutorial, the same file is used for both the model and the result.
  3. Click Apply.


    Figure 2.
Tip: Quickly import the model by dragging and dropping the h3d file from a windows browser into the HyperLife modeling window.

Define the Fatigue Module

  1. From the Setup tools, click the SN tool.
    The SN tool should be the default fatigue module selected. If it is not, click the arrow next to the fatigue module icon to display a list of available options.


    Figure 3.
    The SN dialog opens.
  2. Define the SN configuration parameters.
    1. Select Uni Axial as the method.
    2. Select MPA for the FE model units.
    3. Select Signed von for the stress combination.
    4. Enter a value of 0.5 for the certainty of survival.
    5. Select GOODMAN for the mean stress connection.
    6. Select Top for the layer selection.


    Figure 4.
  3. Exit the dialog.

Assign Materials

  1. From the Setup tools, click the Material tool.


    Figure 5.
    The Assign Material dialog opens.
  2. Activate the checkbox next to the part solid.
  3. If Steel 1045, Annealed, BHN=225 (932) is not the default material assigned to the part:
    1. Click the Material DB tab.
    2. Right-click on Steel 1045, Annealed, BHN=225 (932) and select Add to Assign Material List.
    3. Return to the Assign Material Data tab and select Steel 1045, Annealed, BHN=225 (932) from the Material drop-down menu.
      The Material list is populated with the materials selected from Material Database and My Material.
  4. Optional: Click to review the SN plot.


    Figure 6.
  5. Accept all other default parameters.


    Figure 7.
    Note: The FL (Fatigue Limit) and SE (Standard Error) values are from the SN curve selected for the part. The SE value can be edited from both the Assign Material Data tab and the My Material tab. The FL value can be reviewed and edited from the My Material tab. Parameters updated in the My Material tab will be saved to a user-defined excel spreadsheet.
  6. Exit the dialog.

Assign Load Histories

  1. From the Setup tools, click the Load Map tool.


    Figure 8.
    The Load Map dialog opens.
  2. From the Load Type menu, select Time Data.
  3. Click and browse for load1.csv.
  4. Click to add the load case.
  5. Repeat steps 3 and 4 for load2.csv.
  6. Optional: Click to view a plot of the loads.


    Figure 9. Load 1


    Figure 10. Load 2
    Tip: Expand the width of the dialog to view a clearer picture of the plot.
  7. On the bottom half of the dialog, set the radio button to Manual for event creation and click to create an Event_1 header.
  8. Drag and drop Subcase 1 and Subcase 2 under Event_1.
  9. Drag and drop the Block file under load1 onto the Channels field of Subcase 1.
  10. Repeat for the Block file under load2 and Subcase 2.
  11. Activate the check box for Event_1.
  12. Set LDM to 1.0, Scale to 5.0 and Offset to 0.0 for both subcases.


    Figure 11.
  13. Exit the dialog.

Evaluate and View Results

  1. From the Evaluate tool group, click the Run Analysis tool.


    Figure 12.
    The Evaluate dialog opens.


    Figure 13.
  2. Optional: Enter a name for the run.
  3. Click Run.
    Result files are saved to the home directory and the Run History dialog opens.


    Figure 14.
  4. Once the run is complete, click View Current Results.
  5. Use the Results Explorer to visualize various types of results.


    Figure 15.


    Figure 16.