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Initial conditions, type=hardening - defining backstresses

Initial conditions, type=hardening - defining backstresses

Initial conditions, type=hardening - defining backstresses

(OP)
Dear all,

I have been looking for some information regarding the inclusion of hardening in cold-formed steel beams. First of all, I have defined my material as follows:

*MATERIAL, NAME=steel_corner
*DENSITY
7850e-9
*ELASTIC, TYPE=ISOTROPIC
202870, 0.3
*PLASTIC, HARDENING=KINEMATIC
220, 0
398.73, 0.18637574

Following I wish to include the residual stresses and equivalent plastic strains. Modelling the residual stresses is pretty straight-forward as I used the following definition for the number of through-thickness integration points that I chose. Here I assume that the data input is : NODESET, SECTION POINT, SIGMA11, SIGMA22, SIGMA12 (i am using shell elements).

*INITIAL CONDITIONS, TYPE=STRESS, SECTION POINTS
Beam-1.BOTTOMLIPCORNER, 1, 11, -110,0

My question is related with the definition of the equivalent plastic strains and the necessary adjustments needed to define the yield surface, particularly the definition of the backstresses (coordinates of the yield surface center). I currently have the values calculated for every through-thickness section point but I am not sure what the syntax is to include this information. I understand that I should include the equivalent plastic strain and define the number of backstresses:

*INITIAL CONDITIONS, TYPE=HARDENING, SECTION POINTS, TYPE=HARDENING, NUMBER BACKSTRESSES=n
Beam-1.BOTTOMLIPCORNER, 1, ????

Since i shall be using shell elements, I am assuming 3 backstresses sigma1, sigma2 and sigma3. The sigma2 component is obviously null, given the fact that thickness direction stresses are neglected. sigma1 and sigma3 have been calculated and this is the information that needs to be input. Should the input card look like this?

*INITIAL CONDITIONS, TYPE=HARDENING, SECTION POINTS, TYPE=HARDENING, NUMBER BACKSTRESSES=n
Beam-1.BOTTOMLIPCORNER, 1, EQUIVALENT PLASTIC STRAIN, SIGMA1, SIGMA2 = 0, SIGMA3 (with n = 3)??

Thanks in advance to anyone who can provide me some insight on this particular subject.
Pirs

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