DISP Subroutine in Riks procedure
DISP Subroutine in Riks procedure
(OP)
Hello everybody,
I have made a DISP subroutine and it works correctly in 'Static, General' Step. But when I change to 'Static, Riks' Step an Error arises as 'A zero displacement solution was found in the first iteration of a riks step. The analysis cannot proceed. The most likely cause is that all displacement degrees-of-freedom are constrained to be zero.'
Could you say me what I have to do to run the subroutine in 'Static, Riks' Step?
I attach the part of .inp and subroutine below.
---------------------------------------Input-----------------------------------------------
** STEP: Step-1
**
*Step, name=Step-1, inc=20
*Static, direct, riks
0.05, 1., , , , Set-Node3, 1, 0.8
**
** BOUNDARY CONDITIONS
**
** Name: Disp Type: Displacement/Rotation
*Boundary, user
Set-Barra, 1, 1
Set-Barra, 2, 2
--------------------------------------Subroutine----------------------------------------
SUBROUTINE DISP(U,KSTEP,KINC,TIME,NODE,NOEL,JDOF,COORDS)
C
INCLUDE 'ABA_PARAM.INC'
C
DIMENSION U(3),TIME(2),COORDS(3)
C
Ur=0.5
dx=COORDS(1)-75
dy=COORDS(2)-75
dl2=dx**2+dy**2
dl=sqrt(dl2)
acos=dx/dl
asin=dy/dl
C
IF (JDOF.EQ.1)THEN
U(1)=Ur*acos
ELSE IF (JDOF.EQ.2)THEN
U(1)=Ur*asin
ENDIF
IF (NODE.EQ.3)THEN
WRITE(*,*) 'SUBRUTINA!',NODE,U(1)
ENDIF
RETURN
END
I have made a DISP subroutine and it works correctly in 'Static, General' Step. But when I change to 'Static, Riks' Step an Error arises as 'A zero displacement solution was found in the first iteration of a riks step. The analysis cannot proceed. The most likely cause is that all displacement degrees-of-freedom are constrained to be zero.'
Could you say me what I have to do to run the subroutine in 'Static, Riks' Step?
I attach the part of .inp and subroutine below.
---------------------------------------Input-----------------------------------------------
** STEP: Step-1
**
*Step, name=Step-1, inc=20
*Static, direct, riks
0.05, 1., , , , Set-Node3, 1, 0.8
**
** BOUNDARY CONDITIONS
**
** Name: Disp Type: Displacement/Rotation
*Boundary, user
Set-Barra, 1, 1
Set-Barra, 2, 2
--------------------------------------Subroutine----------------------------------------
SUBROUTINE DISP(U,KSTEP,KINC,TIME,NODE,NOEL,JDOF,COORDS)
C
INCLUDE 'ABA_PARAM.INC'
C
DIMENSION U(3),TIME(2),COORDS(3)
C
Ur=0.5
dx=COORDS(1)-75
dy=COORDS(2)-75
dl2=dx**2+dy**2
dl=sqrt(dl2)
acos=dx/dl
asin=dy/dl
C
IF (JDOF.EQ.1)THEN
U(1)=Ur*acos
ELSE IF (JDOF.EQ.2)THEN
U(1)=Ur*asin
ENDIF
IF (NODE.EQ.3)THEN
WRITE(*,*) 'SUBRUTINA!',NODE,U(1)
ENDIF
RETURN
END





RE: DISP Subroutine in Riks procedure
And since a amplitude is not allowed in Riks steps, since the actual load is part of the solution, I assume a subroutine for the loading is also not allowed.
RE: DISP Subroutine in Riks procedure
The user subroutine DISP posted above should work in both procedures ('Static, General' and 'Static, Riks'). But as I said before in 'Static,Riks' doesn't work. I suspect that something is missing in the input file, if someone has used DISP subroutine in 'Static,Riks' procedure and can show me my mistake, it would be awesome.
Any question ask me, I'm looking forward your responses.
RE: DISP Subroutine in Riks procedure
RE: DISP Subroutine in Riks procedure
Thanks Mustaine3