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how to define a plastic generalized material model in FEAP
Hi all, i've FEAP 7.5 and i'm trying to define a soil stratum for a simply analysis (a 2D plane strain, i.e. §12.7 example 1 on limit analysis of Wai-Fah Chen). In FEAP i've look in inmate.f (not in user_manual) that there's the plastycicy generalized model. I've the cohesion C, the frictional angle PHI, the elastic modulus Ee (nu, the Poisson coefficient relate to PHI). Always in inmate.f I've noted that the related print out instruction - write(iow,2047) - refer to <Yield stress, Yield stress inf, Transition parameter, Hiso, Hkin>. I've also read that in general form the generalized plastic criterion is outlined how:
f = alpha x p + J^1/2 - k <= 0
with alpha and k related to C and PHI.
What's the question???
Someone can help me to understand how to input material parameter ? I've guess that it's some fo:
material nn
solid
elastic isotropic Ee nu
plastic generalized ?? ?? ??
mixed
who are ev(1), ev(2) and ev(3)?
many thanks.
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Hi, maxlox
Hi, maxlox;
I know FEAP is a very famous FEM procedure and I am very interest in it. My question is that whether the code is open an source and could be download free of charege.
TAO ZENG
LML,Polytech-Lille
Cite Scientifique
59655 Villeneuve d'Ascq,France
FEAP material inputs
Maxlox,
The ev(xx) in inmate.f refers to the numerical tags that follow the text inputs. The input lines for the material properites are parsed as text(1) and text(2) for the first two fields and then ev(1), ev(2), ..., ev(10) for the floating-point fields. i.e.
text1 text1 ev1 ev2 .... ev10
If you want pressure dependent yield then you should use the drucker-prager or drucker-lode models in the code.
Tao Zheng,
Feappv is free and can be downloaded from http://www.ce.berkeley.edu/feap/feappv . For the full version of FEAP (see http://www.ce.berkeley.edu/feap ) the cost is $1500 for commercial operations and $750 for educational (and personal) use [perpetual license]. Both the free version (as described in the book of Z. and Taylor) and the full version are distributed as source.
Prof. Dr. Sanjay Govindjee
University of California, Berkeley
ml hi Tao Zeng, how had
ml
hi Tao Zeng, how had said Prof. Sanjay Govindjee FEAPpv (pv -> personal version) can be downloaded from site of Prof. R. Taylor (see the links in Prof. Sanjay post - I think that Sanjay is the surname!) but I don't think if you can use FEAPpv in jobs: Proff. OCZ&RLT says that's only for educational. I'm trying to use FEAP (that I've purchased ...) in my work with much more difficult ... it isn't user friendly! but it's very powerfull if you lear to use. I'm searching for a (FREE) pre-processor & (really) post-processor: the input for FEAP is via an "I_file" in ascii (this' not a problem) but the visualization of results are very "essential"! Another code that I'm trying in this day is SALOME-ASTER (i've installed the CAElinux http://www.caelinux.org/wiki/index.php/Main_Page ... hey but you're in France: more of the documentation is french)
Prof. Sanjay, yes, I've seen that there's 10 ev(i), but in the section Plasticity properties (Mises, Drucker-Prager, Drucker-Lode, Hardening, Linear segment hardening, Viscoplastic & Generalized modal) only 3 of them (ev(1)...ev(3) I've see) are used/input.
Hovewer my problem isn't that. My really problem are the value that I've to input for. If I've C, PHI, Ee, nu, suppose a Drucker-Prager model (d(46)=2.0 ... I think I've an error in comment line of source inmate.f : the Drucker-Lode / d(46)=3.0 it's indicated how Drucker-Prager material)
material nn
solid
elastic isotropic Ee nu
plastic drucker ?? ?? ??
mixed
who are ev(1), ev(2) and ev(3)? are they related with alpha'
and K in the formula (3.101) (pag 62 of OCZ&RLT book, vol 2°, V edition) and how they are related: in the output of material property (inmate.f, instruction write(iow,2047)) print Yields and modulus values.
I've see your page and I know that you've develop routines for FEAP: please explain me how to do.
many thanks.
As they say, read the true manual (the FORTRAN)
Yes it is a bit cryptic since the english manual does not spell out how to use these models. It sounds like you want a pressure dependent yield, i.e. a classical Drucker-Prager model. Use "plastic drucker sig_y_tension sig_y_compression" for Drucker-Prager plus "plastic hardening Hiso Hkin". The "yield radius" and angle can be computed from these values (and is by the code). For example alpha = sqrt(18/3) * (sig_y_c - sig_y_t)/(sig_y_t + sig_y_c). The used yield condition is sqrt(2*J2) + (1/3) * aa * I1 < Y_R where Y_R is the reference yield radius before hardening [ Y_R = sqrt(8/3)*sig_y_c*sig_y_t/(sig_y_t+sig_y_c) ]. If you have hardening this value increases proportionally to the equivalent plastic strain based upon Hiso. Note that this model is only present in finite deformation; if you want small deformation you will need to write your own user model. Also, since this model is not in the manual you should be careful. It may not be fully functional or it may not play well with all other parts of the code. You'll have to test it to make sure.
Prof. Dr. Sanjay Govindjee
University of California, Berkeley
ml italyoops: yesterday
ml italy
oops: yesterday I've had some problem in posting message!
thanks Prof. Sanjay. Now I', thinking/calculating ...... (sig_y_c and sig_y_t ???)
In defining K of formula 3.101 in OCZ&RLT there's a printing error ? there's a Cohesion ?
Yes it's a good idea to implement a user material (I'll look your users routine).
"read the true manual (FORTRAN)": refering to programmer manual of FEAP?
hi .ineed help i need 2d
hi .ineed help i need 2d truse model in feep
true manual == source code
I meant, read the source code, that is the true manual...
Prof. Dr. Sanjay Govindjee
University of California, Berkeley