Fatigue - Random Vibration PropertyManager

A frequency-based fatigue analysis is implemented in cases where the loading and response are random processes and therefore are best described using statistical measures.

To open the Fatigue - Random Vibration PropertyManager:

  • After running a dynamic random vibration study, create a new fatigue study based on stress PSD (power spectral density) results from the random vibration study. Right-click the top icon of the fatigue study tree and click Properties.
Three computational methods are available for computing the expected damage ratio in the frequency domain:
  • Narrow Band Method
  • Steinberg Method
  • Wirsching Method
For more information about the fatigue computational methods, see Simulation Help: Fatigue for Random Vibration Loading.

The vonMises stress component of the PSD function is considered for the calculation of the expected damage due to fatigue for all three methods.

Computation Method

  Narrow Band Method

Selects the Narrow Band method to compute the expected damage ratio due to random loading fatigue.

The vonMises stress component of the PSD function is considered for the calculation of the expected damage due to fatigue for all three methods.
  Steinberg Method Selects the Steinberg method.
  Wirsching Method Selects the Wirshing method.
  Shell face Sets the shell face for which fatigue analysis is performed. Select one of the following:

Top

Performs fatigue analysis for the top shell faces.

Bottom

Performs fatigue analysis for the bottom shell faces.
  Fatigue strength reduction factor (Kf) Use this factor, between 0 and 1, to account for differences in test environment used to generate the S-N curve and the actual loading environment. The program divides the alternating stress by this factor before reading the corresponding number of cycles from the S-N curve. This is equivalent to reducing the number of cycles that cause failure at a certain alternating stress. Fatigue handbooks suggest numeric values for the fatigue strength reduction factor.
  Infinite life The number of cycles to be used when the corrected alternating stress is less than the endurance limit. This number is used instead of the number of cycles associated with the last point of an S-N curve.
  Results folder Sets the folder for the results of the fatigue study.