FEAP User Forum

FEAP => FEAPpv => Topic started by: WANGJIANHUI on December 10, 2022, 03:25:04 AM

Title: Solution of vibration mode
Post by: WANGJIANHUI on December 10, 2022, 03:25:04 AM

Dear user:
           When analyzing the free vibration problem of cracked rock mass, I encountered several problems in the solution process:
         1.In the input file, I used the "SUBSpace,, 10" command to solve the 10 order frequency value, but in the output file, I got the 20 order
            frequency value.
         2.Does the input file use the "DISPlacement ALL" command to obtain the vibration mode solution? I input this command, but why are the
            vibration mode  of each node obtained in the output file all zero?
         3.After the calculation is completed, the Feappv interface will display a vibration mode diagram, and the three-dimensional solid structure
            should get a vibration mode diagram of three components. How to view the other two vibration modes?

            In the attachment are my input file, output file and the obtained vibration mode diagram. I hope the teacher can answer my questions
            and solve my problems. Thank you very much!

Title: Re: Solution of vibration mode
Post by: Prof. S. Govindjee on December 12, 2022, 12:37:50 AM

(1) The subspace algorithm adds extra vectors to ensure that the ones you request are converged.  Make sure to look at the residuals to see if the vectors you requested are converged.

(2) To print the eigenvectors use EIGV,ALL,n  where n is the number of the desired vector, so EIGV,ALL,4  to print the 4th eigenvector.

(3) Plot> eigv,3,,2 will, for example, contour the 2 component of the displacement from the 3rd eigenvector.

Title: Re: Solution of vibration mode
Post by: WANGJIANHUI on December 13, 2022, 10:59:46 PM

Thank you for your reply.

Title: Re: Solution of vibration mode
Post by: WANGJIANHUI on December 15, 2022, 12:58:16 AM

Dear Prof. S. Govindjee：
         I am try to print the eigenvectors use "EIGV,ALL,n", but the output file prompts "*ERROR* Must use SUBS command first"。I have entered the "SUBSpace" command。
         Please check my input file for any errors

Title: Re: Solution of vibration mode
Post by: Prof. S. Govindjee on December 15, 2022, 10:32:18 AM

I ran your input file with the current version of FEAPpv and it seemed to work.  Here is my output file.  (Note I renamed it but it is output from your exact input file).

Title: Re: Solution of vibration mode
Post by: WANGJIANHUI on December 17, 2022, 01:32:01 AM

              I have checked your output file and can output feature vectors. But why does an error occur in the same input file? What is the cause? Attached is my output file.

Title: Re: Solution of vibration mode
Post by: Prof. R.L. Taylor on December 17, 2022, 09:58:15 AM

What version are you using -- I see ver 3.1 from 2013?  Is this FEAPpv?  if it is you should get a new version.  I suspect what you are seeing comes from changes made since that date, one being checking for nonzero "np(77)" instead of positive "np(77)".

Title: Re: Solution of vibration mode
Post by: Prof. S. Govindjee on December 17, 2022, 10:19:01 AM

Definitely update your version:  https://github.com/sanjayg0/feappv