×
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

Shaker load question

Shaker load question

Shaker load question

(OP)
Hello, I am new in vibration domain and I am looking for some information.

I have to perform a random vibration test:
Hz (m/s^2)^2
10 10
100 10
300 0,51
500 5
2000 5
R.M.S. acceleration 96,59(m/s^2)^2
Sigma clipping 3
Necessary force to perform this test is: 66938 N (for 3sigma and my test setup load - it was calculated by the vibration control software).
Available shaker force: 90000N.
I start the test at -6 dB, after that at -3 dB and after at 0 dB. When the acceleration level is at 0 dB I hear some sounds from inside of power modules of shaker amplifier. The sounds is like when a switch is turned on and off, on and off - or a non engineering description- the sound is like when pop-corn is donne. I take a look inside of a power module and I didn’t see any switch.
Can somebody tell me:
- if this sounds are the effect of the acceleration clipping;
- if this sounds are the effect of the test setup load ;
- if a test require 75% or more (but less than 100%) of shaker availability for one of the following parameters: displacement, velocity, acceleration, force, for how many hours the shaker can work in this conditions?

RE: Shaker load question

(OP)
Each power module of the amplifier have a green (OK) and a red (not OK) LED. For the vibration test described above the green LED was ON permanent.

RE: Shaker load question

Closer to 10 g rms.

RE: Shaker load question

Errr...then 3.3 grms? Agree hard to figure out with the units as written.

RE: Shaker load question

Given his stated force requirement, it seems likely that someone glitched a decimal place. 22300N/10g = 227kg, which seems like a plausible number, but it's shouldn't be anywhere near 10g, unless they doing some sort of accelerated life test.

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

RE: Shaker load question

(OP)
The test has to be perform on the slip table. Total weight of all test setup - including moving element of the shaker is aprox. 230 kg.

RE: Shaker load question

OK, someone needs to check the units, the numbers given are not consistent with each other nor with reality. The PSD given, if the units are correct, result in about 98 m/s^2 rms, not 98 (m/s^2)^2, or about 10g rms, which is consistent with the loading on the shaker

Again, 22300N/230kg = 9.9g rms, which is a very severe vibration level.


Is your UUT top-heavy?

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

RE: Shaker load question

(OP)
I'm sorry! The unit for rms value is (m/s^2).
Slip table + copling element + thermal barrier + moving elemet + fixture + screws + UUT's = 230kg

RE: Shaker load question

But, is it top heavy? A standard slip table is prone to rocking if the UUT pushes the CG too high

Have you contacted the manufacturer?

TTFN
FAQ731-376: Eng-Tips.com Forum Policies

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