hello everybody

i want to ask when i use isotropic hardening law in umat abaqus. i used uhard subroutine.

my question can be so simple.

how we will enter plasticity values in abaqus. i think in user material after other constant we enter them like this

for exemple:

props(1) young

props(2) poisson ratio

props(3) strain value for the curve maybe 0

props(4) corresponding yield stress value

props(5) other strain value

......

.....

is this right???

thank`s in advance

hello everybody
i want to develop a constitutive law for fiber reinforced composite. so i am using umat subroutine to simulate it in abaqus.
when i begin analysis i got error code 144.
my question is: is jacobian matrix DDSDDE can be to cause for this error??

and i read that i can use uhard subroutine for isotropic and combined hardening.
using this subroutine we can get yield surface from hardening curve, so we must enter some value in abaqus^material^(yield stress with corresponding strain)

hello everybody.

hello everybody

i want to know what is the meaning of back stress and its effect on drucker prager yield criterion for viscoelasticity materials

thank you 

hello everybody

when i am trying to make a creep analysis using abaqus and it is the first time i do that

when i submit the job, there is an error and a message appear this message is:

ERROR: DEGREE OF FREEDOM 11 AND AT LEAST ONE OF DEGREES OF FREEDOM 1 THRU 6 

           MUST BE ACTIVE IN THE MODEL FOR *COUPLED TEMP-DISP. CHECK THE 

           PROCEDURE AND ELEMENT TYPES USED IN THIS MODEL.

 ***NOTE: DUE TO AN INPUT ERROR THE ANALYSIS PRE-PROCESSOR HAS BEEN UNABLE TO 

          INTERPRET SOME DATA.  SUBSEQUENT ERRORS MAY BE CAUSED BY THIS OMISSION

i am new in using abaqus and also in materials analysis fatigue

so i want to use stress ratio R=-1 and R=0 for analysis an aluminium material

so how to define this in abaqus

is it to take in amplitude (periodic) and define A0 and t0 w also the values of A B? IS THIS CORRECT OR NO

thank you