Random events

You create a random durability event to predict fatigue life and damage for structures that are subject to random loads and that are characterized by a power spectral density. The excitations are defined by a Response Dynamics solution process.

General workflow for random fatigue analysis

• Using the Simcenter Nastran SOL 103 Response Dynamics, compute normal and constraint modes.

• Create a Response Dynamics solution process. Set up a random event and an excitation PSD.

• Create a Durability solution process. Set up and solve a random durability event.

Setting up a random durability event

In the Random Durability Event dialog box, you:

• Specify a Response Dynamics solution process and its random event.

• Define a random fatigue durability object that contains random fatigue settings and fatigue life output requests.

• Define a solve options durability object that contains element and material overrides.

For each element-node, the durability solver computes fatigue life and damage using:

• The Von Mises stress power spectral density (PSD) from the random event of the Response Dynamics solution process.

• Stress life material properties from Pre/Post materials.

To compute the fatigue life and damage results, you can choose between the narrow-band (Miles) method or the wide-band (Dirlik) method. The results from the narrow-band analysis are more conservative than those from the wide-band analysis. Wide-band analysis results generally correlate better with experiments.

Where do I find it?

Application	Pre/Post
Prerequisite	Response Dynamics Random Event
Command Finder	Random Durability Event
Menu	Insert→Durability→Event→Random
Simulation Navigator	Right-click the Durability solution process node→New Event→Random

How do I

Create and solve a random durability event

Learn more

Durability objects

Look up more details

Random fatigue methods

Quick links

Command reference

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Random events, Simcenter 3D 2021.1 Series

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