×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

accelerated vibration test

accelerated vibration test

accelerated vibration test

(OP)
Hello

I am planning an accelerated vibration test on a shaker rig, starting from time-history data of measured accelerations.

My approach is as follows:
- calculate gRMS of measured data
- calculate gRMS of profile to be used on rig for a (say) 3x accelerated testing time, using Coffin-Manson power law
- calculate corresponding acceleration spectral density (g2/Hz)

However I am a bit puzzled as to how to assign the correct PSD to individual frequency ranges.

The first problem is how to allocate PSD figures to individual ranges so to comply with rig limitations (max displacement at low freq) whilst maintaining the overall target gRMS.
Do you think I could filter the measured data through separate bandpass filters, then calculate the gRMS for each frequency range and apply the Coffin-Manson rule to each individual range? After this I could play with PSD values in each interval, as long as I make sure that the overall gRMS is still the same?
 
The second problem is that the rig is only capable of frequencies up to 2kHz and my measured data contains some non-negligible gRMS which falls above this threshold. How can I make use of this data on the rig profile?

Thanks

Gio1

 

RE: accelerated vibration test

(OP)

Hi Greg

I don't have information on the failure of the part, only measured acceleration data on it. The part has never failed in service but I'm trying to achieve a failure on rig through accelerated vibration testing, and I think that using an amplified random vibration based on a measured profile is reasonable, but I'm not sure about my detailed approach, especially as the rig cannot reproduce the full width of the operating spectra  

Cheers
Gio1

RE: accelerated vibration test

For the second part of your question...the shaker can probably go a little higher than 2000 Hz, maybe 2500 or a little higher.  Our Unholtz Dickie T2000 and smaller tables can do 2500 no problem.

However, much beyond 2000Hz and the displacements are very small and therefore much less destructive than lower frequencies.  In my industry, we don't care about things much above 2000hz but maybe that's different for your industry or part.

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!


Resources