simple problem with UMAT

[EvgenAbaqus]

Hello Dears!

could you help me please.

I wrote a small umat subr, but it works doesn't correctly

I have 2 steps

Dens=7800
for Emodulus i use next eq. E=Dens**2.5
at first i define DDSDDE, stess, strain, strain energy denity, and parametr S

if S < some value then Ddens=7800

and then Densnew=Dens+DDens
Enew=Densnew**2.5
in second step i'd like use new Emodulus but stress does not change!!!

Help me Please!! i don't know what to do anymore..!

there is umat and inp file

 

[EvgenAbaqus]

SUBROUTINE UMAT(STRESS,STATEV,DDSDDE,SSE,SPD,SCD,
1 RPL,DDSDDT,DRPLDE,DRPLDT,
2 STRAN,DSTRAN,TIME,DTIME,TEMP,DTEMP,PREDEF,DPRED,CMNAME,
3 NDI,NSHR,NTENS,NSTATV,PROPS,NPROPS,COORDS,DROT,PNEWDT,
4 CELENT,DFGRD0,DFGRD1,NOEL,NPT,LAYER,KSPT,KSTEP,KINC)
C
INCLUDE 'ABA_PARAM.INC'
C
CHARACTER*80 CMNAME
DIMENSION STRESS(NTENS),STATEV(NSTATV),
1 DDSDDE(NTENS,NTENS),DDSDDT(NTENS),DRPLDE(NTENS),
2 STRAN(NTENS),DSTRAN(NTENS),TIME(2),PREDEF(1),DPRED(1),
3 PROPS(NPROPS),COORDS(3),DROT(3,3),DFGRD0(3,3),DFGRD1(3,3)

c elastic property

PARAMETER (ONE=1.0D0,TWO=2.0D0)

E=PROPS(1)
ANU=PROPS(2)
ALAMBDA=E*ANU/(ONE+ANU)/(ONE-TWO*ANU)
AMU=E/(ONE+ANU)/2
DO I=1, NTENS
DO J=1, NTENS
DDSDDE(I,J)=0.0D0
ENDDO
ENDDO
DDSDDE(1,1)=(ALAMBDA+TWO*AMU)
DDSDDE(2,2)=(ALAMBDA+TWO*AMU)
DDSDDE(3,3)=(ALAMBDA+TWO*AMU)
DDSDDE(4,4)=AMU
DDSDDE(5,5)=AMU
DDSDDE(6,6)=AMU
DDSDDE(1,2)=ALAMBDA
DDSDDE(1,3)=ALAMBDA
DDSDDE(2,3)=ALAMBDA
DDSDDE(2,1)=ALAMBDA
DDSDDE(3,1)=ALAMBDA
DDSDDE(3,2)=ALAMBDA
DO I=1, NTENS
DO J=1, NTENS
STRESS(I)=STRESS(I)+DDSDDE(I,J)*DSTRAN(J)
ENDDO
ENDDO

If (KSTEP.eq.2) then
E=111111111111
Endif


RETURN
END​

please check this umat

why in case of second step i have error?

in 1s step i'd like use 1st Emodulus

but in 2 step i'd like use new Emodulus

 

[Mustaine3]

Add your IF loop under the line with E=PROPS(1)

 

[EvgenAbaqus]

nothing happened!
and also i'd like use modulus after calculations of some values
i should to calculate new stress in second step from values which i obtained in first step

please check attached file

SUBROUTINE UMAT(STRESS,STATEV,DDSDDE,SSE,SPD,SCD,
1 RPL,DDSDDT,DRPLDE,DRPLDT,
2 STRAN,DSTRAN,TIME,DTIME,TEMP,DTEMP,PREDEF,DPRED,CMNAME,
3 NDI,NSHR,NTENS,NSTATV,PROPS,NPROPS,COORDS,DROT,PNEWDT,
4 CELENT,DFGRD0,DFGRD1,NOEL,NPT,LAYER,KSPT,KSTEP,KINC)
C
INCLUDE 'ABA_PARAM.INC'
C
CHARACTER*80 CMNAME
DIMENSION STRESS(NTENS),STATEV(NSTATV),
1 DDSDDE(NTENS,NTENS),DDSDDT(NTENS),DRPLDE(NTENS),
2 STRAN(NTENS),DSTRAN(NTENS),TIME(2),PREDEF(1),DPRED(1),
3 PROPS(NPROPS),COORDS(3),DROT(3,3),DFGRD0(3,3),DFGRD1(3,3)

c elastic property

PARAMETER (ONE=1.0D0,TWO=2.0D0)

Dens=PROPS(1)
ANU=PROPS(2)
E=Dens**2.5


ALAMBDA=E*ANU/(ONE+ANU)/(ONE-TWO*ANU)
AMU=E/(ONE+ANU)/2
DO I=1, NTENS
DO J=1, NTENS
DDSDDE(I,J)=0.0D0
ENDDO
ENDDO
DDSDDE(1,1)=(ALAMBDA+TWO*AMU)
DDSDDE(2,2)=(ALAMBDA+TWO*AMU)
DDSDDE(3,3)=(ALAMBDA+TWO*AMU)
DDSDDE(4,4)=AMU
DDSDDE(5,5)=AMU
DDSDDE(6,6)=AMU
DDSDDE(1,2)=ALAMBDA
DDSDDE(1,3)=ALAMBDA
DDSDDE(2,3)=ALAMBDA
DDSDDE(2,1)=ALAMBDA
DDSDDE(3,1)=ALAMBDA
DDSDDE(3,2)=ALAMBDA
DO I=1, NTENS
DO J=1, NTENS
STRESS(I)=STRESS(I)+DDSDDE(I,J)*DSTRAN(J)
ENDDO
ENDDO
c MESIS

S11 =STRESS(1)
S22 =STRESS(2)
S33 =STRESS(3)
S12 =STRESS(4)
S13 =STRESS(5)
S23 =STRESS(6)

STATEV(1)=(((S11-S22)**2+(S22-S33)**2+(S33-S11)**2+6*S12**2+S23**2+S13**2)/2)**0.5
c
c stain
STATEV(2)= STATEV(1)/E

c strain dens

STATEV(3)= (STATEV(1)*STATEV(2))/2

c param S
STATEV(4)= STATEV(3)/Dens

S =STATEV(4)

c define const

b=4.0E-6
f=0.10
S0=2e-11

c algoritm
IF (S.GT.(S0+f*S0)) THEN
DDens= b*(S-(1+f)*S0)
ENDIF

c IF ((S.GT. (S0-f*S0)).AND.(S.LT. (S0+f*S0))) THEN
c DDens = O
c ENDIF

IF (S.LT. (S0-f*S0)) THEN
DDens= 7800
ENDIF


c new dens

If (KSTEP.eq.2) then
Densnew=Dens+DDens
Enew=Densnew**2.5
E=Enew
Endif
ALAMBDA=E*ANU/(ONE+ANU)/(ONE-TWO*ANU)
AMU=E/(ONE+ANU)/2
DO I=1, NTENS
DO J=1, NTENS
DDSDDE(I,J)=0.0D0
ENDDO
ENDDO
DDSDDE(1,1)=(ALAMBDA+TWO*AMU)
DDSDDE(2,2)=(ALAMBDA+TWO*AMU)
DDSDDE(3,3)=(ALAMBDA+TWO*AMU)
DDSDDE(4,4)=AMU
DDSDDE(5,5)=AMU
DDSDDE(6,6)=AMU
DDSDDE(1,2)=ALAMBDA
DDSDDE(1,3)=ALAMBDA
DDSDDE(2,3)=ALAMBDA
DDSDDE(2,1)=ALAMBDA
DDSDDE(3,1)=ALAMBDA
DDSDDE(3,2)=ALAMBDA
DO I=1, NTENS
DO J=1, NTENS
STRESS(I)=STRESS(I)+DDSDDE(I,J)*DSTRAN(J)
ENDDO
ENDDO
c MESIS

S11 =STRESS(1)
S22 =STRESS(2)
S33 =STRESS(3)
S12 =STRESS(4)
S13 =STRESS(5)
S23 =STRESS(6)

STATEV(6)=(((S11-S22)**2+(S22-S33)**2+(S33-S11)**2+6*S12**2+S23**2+S13**2)/2)**0.5

RETURN
END​