×
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

Using shaker table to verify dynamic frequency based strain

Using shaker table to verify dynamic frequency based strain

Using shaker table to verify dynamic frequency based strain

(OP)
I purchased an IOTech strain book with the intent of measuring strain of components on a shaker table (3300 lbf single axis TIRA )and on lawn and garden applications during normal usage. This would be used to verify that the shaker was replicating the strain levels seen in the field. Once the strain levels on the shaker are verified to the field the next step is compare strain levels to FEA results.

I currently use ABAQUS mode based solution which gives stress as a function of frequency. I want to compare FEA to test values of frequency based strain.  When I take time-based test strain measurements and pass them through a FFT I am getting suspiciously low frequency based test strain values. So I need a way to verify the frequency based strain results I am getting.


To verify this I was planning on putting a gage bar on the shaker table with an accelerometer on the end of the gage bar. The accelerometer would give the displacement at any given frequency. Knowing the displacement the bending stress could be calculated through closed form solutions.
Then I a have a theoretical frequency based solution which can be compared to the value the strain data ac is giving me.

Has anybody came across this before? Does anybody see any issues with this? Feedback would eb appreciated.

TIA,

George Vandyke
Product Engineer
Briggs & Stratton

RE: Using shaker table to verify dynamic frequency based strain

CaptainCrunch:  What frequencies are you using to drive the shaker, what is the profile?  What are your results?  What frequencies do you experct to see?

RE: Using shaker table to verify dynamic frequency based strain

(OP)
Tha shaker will be driven with a low amplitude sign sweep. Say 5 -400 Hz at 0.1 g, sweep rate of 0.2 Hz / sec. I will be looking at all frequencies in this range (resonant and non-resonant). At each of these frequencies the displacement will be given by the accelerometer and be used to calculate the stress through a closed form solution.

RE: Using shaker table to verify dynamic frequency based strain

CAPTAIN CRUNCH:  I suggest that you use a low level random profile.  I would also suggest several accelerometers on the piece so you can see the response of the different locations.  If you shaker feedback accelerometer is on the shaker head you may want to compare its output to the output of the accelerometers on the piece.  Sometimes you are better off mounting the feedback accelerometer on the piece rather than the shaker head.

I am curiois is this an entire engine or jsut a part of it?  I am assuming there is a attaching fixture between the piece and the shaker table.

Regards
Dave
  

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