×
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

Natural frequency of two different materials in one system

Natural frequency of two different materials in one system

Natural frequency of two different materials in one system

(OP)
Hi all,
I am working on a truck part which consists of one composite and one steel hollow part. I have the critical range of vibration frequency and I am able to calculate the frequency of steel part. However, composite part will be designed and mounted to the steel part. Therefore, I try to get some values to decide on the content of the composite part. I am confused about the natural frequency of the composite part. Should it be around the natural frequency of steel part or should complete system's frequency be out of the critical range?
Thanks for your help.

RE: Natural frequency of two different materials in one system

if you can have the natural frequencies of both parts out of the critical range then you are less likely to exist them in a (random) vibration environment

RE: Natural frequency of two different materials in one system

(OP)
Thanks for your reply JXB0809. Do you think whether mounted parts should have similar natural frequencies separately? Or does not it make any sense?

RE: Natural frequency of two different materials in one system

mecmert,

You have two vibration problems. The composite part has its own vibration modes. It sounds like your steel part is a spring with the mass of your composite part fixed to it, and this has a natural circular frequency ω=sqrt(k/m).

--
JHG

RE: Natural frequency of two different materials in one system

If you have two separate SDOF systems with their own natural frequencies, when you bolt them together then the frequencies will change. I realise you are working on top secret components that nobody else has ever seen, but if you could give us some idea of what you are actually trying to do then I dare say I can be more helpful.

Cheers

Greg Locock


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

RE: Natural frequency of two different materials in one system

(OP)
Basically there is a steel pipe. Composite part will be overmolded on the steel pipe to connect both parts instead of using bolts. Then connected parts will be assembled to the system with the connection interface on the composite part. Since truck is exposed to harsh vibration due to rough road and part carries some weight which causes bending, I try to be sure that new design can withstand these contidions theoretically. Therefore, as a beginning, I decided to make some calculation related to natural frequencies to limit the required properties of the composite. Then I will try to plan next steps.

RE: Natural frequency of two different materials in one system

mecmert,

Here is another failure scenario.

You have two pieces connected by a moulded composite fitting. The pieces are bolted at opposite ends. If the opposite ends move, how strong is your moulded composite to metal interface? How flexible is your composite?

--
JHG

RE: Natural frequency of two different materials in one system

From a philosophical perspective, I don't see why one would intentionally design an operational system where the natural frequencies of the subcomponents are intentionally aligned, except for the case where you actually want violent oscillations.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Natural frequency of two different materials in one system

agree with IRstuff. The key input to consider/bear in mind is the freq. range of operation. If say it's 10-100Hz then it doesn't matter if the natural frequencies of the subcomponents are identical what is the chance of that!) if these are much higher than 100Hz (say 400Hz). Mecmert would need to clarify this.

RE: Natural frequency of two different materials in one system

" I don't see why one would intentionally design an operational system where the natural frequencies of the subcomponents are intentionally aligned"

That is of course the exact ideal tune for a harmonic damper.

Cheers

Greg Locock


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

RE: Natural frequency of two different materials in one system

If i understand well, when they are moulded together, it is one stiffness, and one mass, it won't behave as two different systems.

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


Resources

White Paper - How ESI is Helping Move New Medical Device Product to Market Quicker & More Cost Effic
Early Supplier Involvement has long been a strategy employed by manufacturers to produce innovative products. Now, it almost seems like a necessity. Because decisions made in the design phase can positively affect product quality and costs, this can help add value to OEM bottom lines. This white paper will discuss many facets of ESI, including why it’s so valuable today, what challenges limit the benefits of ESI, how cost is impacted, and more. Download Now
White Paper - Moving to a Driverless Future
This white paper describes what we see as the best practices to support a sustainable engineering process for autonomous vehicle design. It exposes how to use simulation and testing in common frameworks to enable design exploration, verification and validation for the development of autonomous cars at a system, software and full-vehicle level to drive a mature product development process for automated driving. Download Now
Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. 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