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# Defining variables in UMAT

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Posts: 5
Topic starter
(@Amir Shahidi)
Active Member
Joined: 15 years ago

Hi Jorgen,

Ive been struggling to use a UMAT routine in Abaqus for some months now. I have just had a chat with a chap who understands quite a lot about Abaqus and he reckons that my problem could be with the way my variables are defined in the code. How should I define the integers in the UMAT?

A quick example of the code:

...

PARAMETER(ZERO=0.D0, ONE=1.D0, TWO=2.D0, THREE=3.D0, SIX=6.D0, &

ENUMAX=.4999D0, NEWTON=10, TOLER=1.0D-6, GRAVITY=0.981E-05)

....

SIGMASTRESS=STRESS*-1

MODSTRESS=STRESS*-1

MODSTRESSTEST=STRESS*-1

IF(TIME(1)>0) THEN

SIGMASTRESS=SIGMASTRESS/TIME(1)

MODSTRESS=MODSTRESS/TIME(1)

MODSTRESSTEST=MODSTRESSTEST/TIME(1)

....

DO K1=1, NTENS

IF (SIGMASTRESS(K1)<0) THEN

SIGMASTRESS(K1)=0.001

END IF

END DO

Will it make a difference if I do:

...

PARAMETER(ZERO=0.D0, ONE=1.D0, TWO=2.D0, THREE=3.D0, SIX=6.D0, &

ENUMAX=.4999D0, NEWTON=10, TOLER=1.0D-6, GRAVITY=0.981E-05, [COLOR=Red]MONE=-1.D0[/COLOR], [COLOR=Magenta]ZZONE=.001D0[/COLOR])

....

SIGMASTRESS=STRESS*[COLOR=red]MONE[/COLOR]

MODSTRESS=STRESS*[COLOR=red]MONE[/COLOR]

MODSTRESSTEST=STRESS*[COLOR=red]MONE[/COLOR]

IF(TIME(1)>[COLOR=Green]ZERO[/COLOR]) THEN

SIGMASTRESS=SIGMASTRESS/TIME(1)

MODSTRESS=MODSTRESS/TIME(1)

MODSTRESSTEST=MODSTRESSTEST/TIME(1)

....

DO K1=1, NTENS

IF (SIGMASTRESS(K1)<[COLOR=green]ZERO[/COLOR]) THEN

SIGMASTRESS(K1)=[COLOR=Magenta]ZZONE[/COLOR]

END IF

END DO

Many thanks

Lelio

PS: This code Im using is not mine, but Ive been assured it should work as it is! It is written in free format, so I added cDEC\$ FREEFORM the command in the beginning of the code so that Abaqus will read it accordingly.

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

That is a common question. I happen to have strong opinions about Fortran 77 (dont use it), and Fortran 90 (much better).

You might want to check out my previous post on the [URL= http://polymerfem.com/forums/showthread.php?t=576 ]subject[/URL].

-Jorgen

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