×
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

how to get the cantilever's amplitude under resonant frequency ANSYS

how to get the cantilever's amplitude under resonant frequency ANSYS

how to get the cantilever's amplitude under resonant frequency ANSYS

(OP)
I am tyring to get the resonant frequency of a microcantilever. I built the model using solid element (solid185), then A Block Lanczos Modal Analysis was applied to the model, after solving, i can get the exact frequencies, but the shown DMX value is on the scale of e+6, instead of e-6, incredibly huge.
Can anybody give me some advices?
I really appreciate any help.  

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

There's an ANSYS Forum here under "Engineering Computer Programs".  You may have more comments there.  How is the piece restrained?  Is Mx a restraint or an applied load?  It looks to be a torque. (Given the coordinate directions (x,y,x) as shown.)

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

(OP)
hi, BobM3, thank you for your comment.
As a cantilever, one end is fixed, while another end is free, which shows the amplitude. But in my analysis, the frequencies values are correct, the amplitude should be on the scale of the micrometer sale, from the result you can see it is meter e6 now. I have no idea what the problem is. I didn't give any load or torque, only used modal analysis.
Thank you.

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

It probably depends on the mass scaling used for the modal analysis, the two main scales are "unity maximum" and "unity modal mass".

Remember that modeshapes are just shapes. They do not have scale.

M

--
Dr Michael F Platten

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

The amplitude of the forces exiting the motion determine the amplitudes. It is the next step in your analysis.  

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

Is it possible that driving a spring-mass system with a really high Q (Silicon?) results in a high amplitude (not actually achieable before failure)?

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

sreid, the OP looking at the results of a modal analysis not a forced response analysis. This is a mode shape not a displacement response.

guoren, if you want to look at the displacement response then you need to do as hacksaw says and apply a dynamic force and look at the response.

M

--
Dr Michael F Platten

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

(OP)
Thanks very one for giving advices.
Dr Michael F Platten, how can I apply a dynamic force for amplitude, by exerting force or pressure on the free end of the cantilever, but each time I can only give one force value instead of a series of, I really appreciate the help from you.  

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

Guoren,

  There are options to input variable force with respect to time using tables in ansys...You can refer www.ansys.net or www.xansys.org for leads....

  But it is preferrable to perform the  response analysis in frequency domain rather than in time domain.

 also based on the characterictics of the system,if the response can be captured using modal space (modal super-position) method then it is preferrable and econmical rather than direct(physical) method.

Regards,
Elogesh

RE: how to get the cantilever's amplitude under resonant frequency ANSYS

In order to get the response of the cantilever you need to run a harmonic response analysis in ANSYS. For a harmonic response analysis you need either displacement or force as an input boundary condition.  You also need to apply some sort of damping to your model.  When setting up the solution you supply a frequency range that you want the response calculated over.



 

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