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Problems with non-linear materials

Problems with non-linear materials

Problems with non-linear materials

(OP)
Hi, I am modelling a metallic structure with Ansys. The idea is to verify the behavior and the distribution of stresses on the structure as the load applied is incremented. When I saw the results I realized that the stresses were greater than yield stress defined by BKIN command what was impossibie because I used a tangent modulus equal to 0.

I decided to make a simple model (beam with tensile force) to verify the behavior of the material, and I found out that when I use a cross section different than ASEC subtype, the beam works perfectly; but when ASEC subtype is used the beam behavies as perfectly elastic   material: doesn't work as BKIN material.

The problem is that I have to use an ASEC subtype because I don't have the geometric data, I just have the geometric properties of the cross section(Area, Izz....)

This is the code of the beam simple model. In this case I used a tangent modulus different than 0 because i didn't want the beam to collapse so this is just a ficticious value. The properties of ASEC section are the same as the I beam.

/prep7

MPTGEN,1,10,0,65
MP,EX,1,206e9,-0.04326e9,-3.502e4,-65.92
MP,PRXY,1,0.28737362,2.5302417e-5,2.6333384e-8,-9.941958e-11,1.2617779e-13
MP,CTEX,1,1.1766e-5,1.1258e-8,1.6550e-12,-1.29356e-14
MPDATA,DENS,1,,7849
TB,BKIN,1,6,1
TBDATA,,372316926,50E9,,,,




k,1,0,0         ! Keypoints
k,2,0,1
l,1,2           ! Line connecting keypoints
  
ET,1,beam188          ! Element type

!SECTYPE,1,BEAM,ASEC,EC143F75,0
!SECOFFSET,CENT

!SECDATA,0.21386E-02,0.20961E-4,0.44734E-20,0.87416E-6,0.13116E-7,0.17553E-7,0.16E-16,0.12535,-.27E-13,0.1535

SECTYPE, 1, BEAM, I, , 0
SECOFFSET, CENT
SECDATA, 0.100330, 0.100330, 0.250698, 0.005182, 0.005182, 0.004572


  
ESIZE,5         ! Element size 5
LMESH,all          ! Line mesh all lines

FINISH  
/SOLU            ! Enter solution phase

NSUBST,40,1000,1    ! 20 load steps
OUTRES,ALL,ALL        ! Output data for all load steps
AUTOTS,ON        ! Auto time-search on
LNSRCH,ON        ! Line search on
NEQIT,1000        ! 1000 iteration maximum
 
ANTYPE,0        ! Static analysis
DK,1,all        ! Constrain keypoint 1
FK,2,FY,20E5       ! Load on keypoint 2

SOLVE
FINISH

/POST1            ! Enter post processor
/ESHAPE,1        ! Show element shape
PLNSOL,U,Y,0,1        ! Plot deflection contour

FINISH

/POST26            ! Enter time history
RFORCE,3,1,F,Y        ! Reads force data in variable 2
NSOL,2,2,U,Y        ! Reads y-deflection data into var 3
XVAR,2            ! Make variable 2 the x-axis
PLVAR,3    
/AXLAB,Y,LOAD         ! Changes y label
/AXLAB,X,DEFLECTION    ! Changes X label
/REPLOT


There you can see the difference between the ASEC and I cross-section.
Could anybody tell me how i can solve this problem?



 

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