FEAP User Forum

FEAP => General questions => Topic started by: shenrilin on May 06, 2017, 04:52:01 PM

Title: Questions about newton-iteration in feap
Post by: shenrilin on May 06, 2017, 04:52:01 PM

Dear all,

I'm using feap to solve a  2D linear elastic problem. When I output strain, stress, displacements etc. of the first iteration in a new time step. I found that all these terms same as their values in last time step. I attached two figures to describe the two sequential time steps. My question is:

what's the purpose of the first iteration?

Thank you very much.

Title: Re: Questions about newton-iteration in feap
Post by: Prof. R.L. Taylor on May 06, 2017, 06:06:03 PM

1. What is the solution set of commands you are using to produce the posted files?

2. What is the loading history for the problem?



the information you give is not sufficient to provide an answer.

Title: Re: Questions about newton-iteration in feap
Post by: shenrilin on May 06, 2017, 07:02:18 PM

Dear Prof. Taylor,

Thanks for your reply.  Although The iteration confused me but the final results are correct.

The model is a bar. one end is fixed and the other side is applied linearly increasing displacement loads.
The solution command is:

Code: [Select]

BATCh
  PETSc,ON
  DT,,dt
  TRANsient,NEWMark,0.5,1.0
  STRE,NODE
  PVIE,NEWSM
  LOOP,,ni
    LOOP,,np
      TIME,,tt
      AUTO,DT,dt,dt
      LOOP,,15
        UTAN,,1
        !TOL,ITER,1.0e-16,1.0e-16,1.0e20
        !UTAN,DMPN,1,,1.0
        !UTAN,LSBA,1.0
      NEXT
    NEXT
    STRE,NODE
    PVIE
  NEXT
  DISP ALL
END
Best,