×
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

Ultrasonds in stressed bolts

Ultrasonds in stressed bolts

Ultrasonds in stressed bolts

(OP)
Hi, I am developing a device that measures the tensional stress in the bolt by using ultrasonic resonances.

My problem is that I have carried out experiments and have observed an increase in resonant frequencies as the bolt becomes stressed. This does not seem to be consistant with the formula f=v/lambda as v decreases and lambda increases as the bolt is stressed. I realise this could be to do with transverse modes forming in the bolt which are dependend on tension, however in my setup there should only be longitudinal modes travelling up and down the bolt.

Another interesting factor I have observed is that the resonant peaks appear to get closer together for higher harmonics

If you have any possible reasons for this please submit them even if they are just areas I shold look into

Thank you

RE: Ultrasonds in stressed bolts

Can you calculate the approximate location (distance from transducer) of the peaks that you are seeing?  Maybe tension is opening up a flaw?  Another possibility is that the transducer coupling is being strained during bolt loading, resulting in artifacts in your data.  A final thought is that somehow the supporting/loading structure is becoming a parasitic path as the bolt is tensioned, due to better contact between bolt and structure as load is applied...

RE: Ultrasonds in stressed bolts

Are you sure that you are not just measuring the widely accepted phenomenon that the joint is getting stiffer as the bolt tension is increased?

I'm a bit suspicious of your formula, why is lambda increasing (other than the bolt stretching which is not measurable I should think).

For that matter why does v decrease?

Cheers

Greg Locock

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