FEAP User Forum

FEAP => FE^2 => Topic started by: Paolo Di Re on January 29, 2019, 09:07:56 AM

Title: Periodic Cauchy input from file
Post by: Paolo Di Re on January 29, 2019, 09:07:56 AM

Dear All,
I'm trying to compute average properties of an RVE using the command "PERIodic CAUChy FILE" and "HILL READ" + "HILL CLOSE", as indicated at page 68 of the user manual (FEAP version 85), but the commands seem not to work. This is what I'm doing exactly:

1 - I have run a FE2 analysis of a linear elastic homogeneous cube using 3D solids at the macro-scale; the RVE is a linear elastic homogeneous cube as well (it's just a benchmark). Everything considers small strains. I have used the command "RVE POINT nn" to obtained the file "F_nn" with the strain history of the nn-th RVE.

2 - I have renamed the "F_nn" file as "RVEHist.txt", here attached.

3 - I have prepared the attached input file "iRVE_PostwHistFileManual.txt" to be run with a serial version of FEAP. This contains the command:

    PERIodic CAUChy FILE
     RVEHist.txt

    during the mesh definition, and the solution is performed as:

    MACRO
      DT,,0.1
      TOL,ENER,1e-12
      LOOP,Time,10
        TIME
        HILL READ
        LOOP,,50
          TANG,,1
        NEXT
        HILL STRESS
      NEXT
      HILL CLOSE
    END

As you can see from the output file, FEAP reads the strains contained in the file, but the average stresses are always zero and no plot is performed.
It looks like it is not actually passing the strains to the elements.

What am I doing wrong?

Thank you in advance for your help.
Paolo

Title: Re: Periodic Cauchy input from file
Post by: Prof. R.L. Taylor on January 29, 2019, 09:53:35 AM

There is a bug in the file input.  In subroutine pmacr1.f  the input of each record is loaded into gradu in stead of gradu0 -- it needs to be changed in several lines to read:
          if(.not.exst) then
            open(unit=97, file=perifile, access='sequential')
          endif
          if(finflg) then  ! Load from deformation gradient
            read(97,*,end=8000) (td(i),i=1,10)
            kk   = 1
            do j = 1,3
              do i = 1,3
                kk         = kk + 1
                gradu0(i,j) = td(kk)
              end do ! i
            end do ! j
            grdbarn(:,:) = grdbar(:,:)
          else             ! Load from strains
            read(97,*,end=8000) (td(i),i=1,7)
            do i = 1,3
              gradu0(i,i) = td(i+1)
            end do ! i
            gradu0(1,2) = td(5)*0.5d0
            gradu0(2,1) = gradu0(1,2)
            gradu0(2,3) = td(6)*0.5d0
            gradu0(3,2) = gradu0(2,3)
            gradu0(3,1) = td(7)*0.5d0
            gradu0(1,3) = gradu0(3,1)
            epsbarn(:)  = epsbar(:)
          endif
          ttim = td(1)
          write(iow,2031) ttim
          call mprint(gradu0,3,3,3,'GRAD U')
        endif

Title: Re: Periodic Cauchy input from file
Post by: Paolo Di Re on January 30, 2019, 01:56:15 AM

Dear Prof. Taylor,
thank you very much for your quick answer.
It fixed the issue.
Best regards,
Paolo