How to Perform a Random Vibration Analysis — Lesson 1

Random vibration analysis enables you to determine the response of structures to vibration loads that are random in nature. The randomness is a characteristic of the excitation or input.  Typical applications include loads experienced by an aircraft in flight, delivery trucks running on rough roads, and wave loading on offshore structures. Many random processes follow a Gaussian distribution, also referred to as a normal distribution.  The excitation is assumed to follow a Gaussian distribution.  The 1-sigma value represents occurrence 68.3% of the time, while 3-sigma values represent occurrence 99.7% of the time.  In a random vibration analysis, since the input excitations are statistical in nature, the output responses such as displacement and stress are also.  At Ansys, the spectral density response is typically called a response power spectral density (RPSD). In this video, we will see how to perform a random vibration analysis using Ansys Mechanical, followed by a walkthrough demo.

Alternate video link.

Video Highlights

0:12 – Introduction to Random Vibrations

1:50 – What is Power Spectral Density?

2:51 – How to Evaluate Random Vibration Excitations

3:22 – Gaussian/Normal Distribution

3:58 – What is Response PSD?

7:05 – How to Input PSG G Acceleration?

8:08 – Retrieving 1-Sigma Deformation Results

8:39 – Retrieving Response PSD with the Response PSD

9:07 – Interpreting 1-Sigma Deformation and Response PSD Results

Simulation Files

Download the accompanying archived project file used in the video lesson here. Ansys Student can be downloaded for free here.