Configure Fatigue Analysis Using the SN Method

Use the SN tool to calculate fatigue based on stress life.

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 1.

   The SN dialog opens.

   
   
   Figure 2.

2. Define the fatigue parameters.
   1. Select an axial method.
      Solid models are not compatible with multiaxial analysis. Currently, only shell elements are supported.
   2. Select the FE model units.
      This unit is necessary because the SN/EN curve might be defined in a different unit, and FEA stress needs to be converted before looking up the fatigue life for a given stress level on the SN curve.
   3. Select a stress combination.
      All the stress tensor result types from HyperView are available to be selected for the fatigue calculation.

      Note: This option is only available for uni-axial analyses.
   4. Based on the scatter of the SN curve, enter a real value between 0 and 1 for the certainty of survival.
   5. Select a mean stress correction option.
   6. Define the Tension and Shear damage models.
      Note: This option is only available for multi-axial analyses.

      You can choose to evaluate one or both of the damage models. Whichever damage from the two models is worse will be displayed after evaluation.

   7. Choose a layer selection.
      If the layer is a shell, fatigue calculation will be done both on top and bottom.

      Note: If the model has only solid elements, you can only perform uniaxial fatigue, and Top or Worst should be the layer selection.