How to Correctly Interpret PSD Results — Lesson 3

We experience random vibrations in day-to-day life, such as while traveling or from a breeze we feel on our face. To study the structures subjected to random vibrations where there is uncertainty in the loading, we utilize random vibration analysis. The input of this analysis follows a Gaussian distribution and is statistically represented as a power spectral density. Because the input is uncertain, the output of this analysis is statistical in nature as well. As a result, the directional outcomes, such as stresses, cannot be combined in the usual way; therefore correctly interpreting the results is crucial. In this video, we will discuss the importance of interpreting the results of a random vibration analysis using Ansys Mechanical correctly and how to do so.

Alternate video link.

Video Highlights:

1:06 - Statistical Nature of the Results/Output

2:15 - Scale Factor for RMS Results (1-sigma, 2-sigma, and 3-sigma)

2:58 - Derived Results/Derived Quantities

4:38 - Solution Coordinate System

5:08 - Importance of Element Orientation

5:43 - Response PSD Tool and benefits

5:58 - RPSD Definition

6:29 - RMS Definition

6:44 - Expected Frequency Definition

8:39 - Setting Element Orientation

9:04 - Requesting Sufficient Modes

10:01 - Participation Factor Listing

10:35 - Input PSD Specification

11:30 - Random Vibration Results

15:10 - Relative vs. Absolute Results

16:33 - Frequency Clustering

Simulation Files

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