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

Free body analysis

Free body analysis

Free body analysis

Is it good practice to model body that have constraint as a free body for resonance analysis?

RE: Free body analysis

if resonance analysis means modal analysis, then I don't think it matters. I think if there are rigid body freedoms in a modal analysis then either the results make it clear (and you disregard), or the results understand these are rigid body motion and doesn't output them.

another day in paradise, or is paradise one day closer ?

RE: Free body analysis

For finding out natural frequency of system to check resonance, it is required to know the natural frequency of system and not particular free body of that system. Body has different natural frequencies and mode shapes when behaving alone and when behaving in a system.

E.g. Cantilever beam(System) that is fix-free beam have different mode shapes and natural frequencies than only beam(Body) with no support that is free-free beam. Here the fixity of one end increases the stiffness of beam and give different mode shapes and natural frequencies than free-free beam.

RE: Free body analysis


I am not getting your point here or OP's question. Could you explain your point with more information?

Pin-Pin beam is allowed to rotate only in the axis normal to depth of beam keeping all other movements fixed. How is the frequency of Pin-Pin beam will be lower than the free-free beam? Free-free beam will have near zero frequency with random mode shapes which is not at all comparable to pin-pin beam which have frequency of positive number and mode shape across/along the flexural direction.

RE: Free body analysis

Still not understood the point here.

Maybe I need to understand what is double point that you mentioned.

Maybe I need to understand more about mathematical assumption of sinusoidal waveform of natural vibration which prove that free-free beam have high frequency than pin-pin beam except translation modes and zero frequency of free-free beam and Clamp-Clamp beam have same frequency as that of free-free beam.

But what about the actual scenario?

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


White Paper - Implementing a Multi-Domain System
IoT systems are multi-domain designs that often require AMS, Digital, RF, photonics and MEMS elements within the system. Tanner EDA provides an integrated, top-down design flow for IoT design that supports all these design domains. Learn more about key solutions that the Tanner design flow offers for successful IoT system design and verification. 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