Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Calculation of Response acceleration PSD in Random Vibration Analysis

Calculation of Response acceleration PSD in Random Vibration Analysis

Calculation of Response acceleration PSD in Random Vibration Analysis


When I plot the response acceleration PSD vs Frequency curve, for each frequency there will be an acceleration PSD value. For example, if the frequency range is 1 to 1000 Hz, at 100 Hz, the PSD value is 0.5g^2/Hz. At 500 Hz, the psd value is 0.1 g^2/Hz, and so on. If we are talking about linear Random Vibration Analysis that based on modal superposition theory, how does the software calculate the response PSD at a specific frequency? Does this calculation involve all the mode shapes up to that specific frequency? In other words, for PSD value at 1000 Hz, was it computed based on the combination of all the modes up to 1000Hz? or was it computed based on just the mode shape at or nearest to 1000 Hz?

I hope my question is clear. Let me know if more clarification is needed. Any comments or resources would be much appreciated.


RE: Calculation of Response acceleration PSD in Random Vibration Analysis

It should be using every mode at every frequency, using the damping dependent SDOF response of each mode. If it ignored the contribution from higher frequency modes you wouldn't see antiresonances.


Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - Considerations for choosing a 3D printing technology
The adoption of 3D printing into major companies’ product development life cycles is a testament to the technology’s incredible benefits to consumers, designers, engineers and manufacturers. While traditional production methods have limitations in manufacturability, 3D printing provides unparalleled design freedom due to the additive method of building parts layer by layer. Download Now
White Paper - Are all 3D printed metals the same?
With so many different 3D printing metal systems and processes today, how can you know exactly what you’re getting? Today, there are several different methods for manufacturing 3D printed metal components with their own strengths and limits. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close