Hi,

I am recently trying to read data from external files into ABAQUS by subroutines like USDFLD, which will finally be used to modify material behavior in UMAT. However, when I code with Fortran in USDFLD, I encounter some strange issues:

1. Writing seems not a problem, but reading with Read(10,*, IOSTAT = IOS) VALUE, for example, will lead to the following issue if I want to use IOS as an identifier for the end of the file: forrtl: severe (24): end-of-file during read. I solve it by adding another dummy line of data at the end of the file, but I am wondering why the way with IOS does not work since I also tried the same code outside ABAQUS with the same Fortran compiler and it works quite well.

2. In the USDFLD as shown below, I try to read data into vectors and strings I define in the subroutine. However, it seems that I always need to do something like WRITE(*,*) 'NO MORE WAITING' to carry on the simulation, otherwise I will get stuck after finishing the first increment in the first step, which can be seen from the .sta file. I feel this has something to do with flushing the buffer since writing to default file (.log) includes the flushing, but I still do not know the reason for this.

   Thank you!

         SUBROUTINE USDFLD(FIELD, STATEV, PNEWDT, DIRECT, T, CELENT,
        1 TIME, DTIME, CMNAME, ORNAME, NFIELD, NSTATV, NOEL, NPT, LAYER,
        2 KSPT, KSTEP, KINC, NDI, NSHR, COORD, JMAC, JMATYP, MATLAYO, LACCFLA)
   C
         INCLUDE 'ABA_PARAM.INC'
   C
         CHARACTER*80 CMNAME, ORNAME
         DIMENSION FIELD(NFIELD), STATEV(NSTATV), DIRECT(3,3), T(3,3), TIME(2)
         DIMENSION ARRAY(15), JARRAY(15), JMAC(*), JMATYP(*), COORD(*)
   
   C     Variables for moisture fields at the start and end of the step
         REAL*8 STEPT, MOISTA, MOIEND, MOIINT
   
         INTEGER IOS, NUMVAL, ITER, ITETOT
         REAL MOFDST(100), MOFDEN(100), XX(100)
   
         CHARACTER*100 MOIFIL, STAFIL, UPDSTA
         MOIFIL = '/home/youwang/Desktop/HT-FEM/moisture_data.csv'
         STAFIL = '/home/youwang/Desktop/HT-FEM/update_state_delphin.txt'
   
         IF (KINC .EQ. 1) THEN
   C     Loop to check if the moisture data file is ready
               ITETOT = 0
   3000        ITER = 0
   3001        ITER = ITER + 1
               IF (ITER .GT. 1000) THEN
                     OPEN(16, FILE=STAFIL, STATUS='OLD')
                     READ(16,*) UPDSTA
                     CLOSE(16)
                     IF (UPDSTA .EQ. 'READY') THEN
                           OPEN(18, FILE=MOIFIL, STATUS='OLD')
                           NUMVAL = 0
   
   1001                    CONTINUE
                           NUMVAL = NUMVAL + 1
                           READ(18,*,IOSTAT=IOS) XX(NUMVAL), MOFDST(NUMVAL), MOFDEN(NUMVAL)
                           IF (XX(NUMVAL) .EQ. 111) THEN
                                 NUMVAL = NUMVAL - 1
                                 GO TO 2000
                           END IF
                           GO TO 1001
   2000                    CLOSE(18)
                           GO TO 2001 ! Exit loop if data is successfully read
                     END IF
                     ITETOT = ITETOT + 1
                     IF (ITETOT .GT. 5) THEN
                           WRITE(*,*) 'NO MORE WAITING'
                           GO TO 2001
                     END IF
                     GO TO 3000
               ELSE
                     GO TO 3001
               END IF
   C        In the first increment, access the step duration (e.g., from FIELD(3)) and read the moisture data
   2001     STEPT = FIELD(3)  ! Access passed step duration from Python
            STATEV(2) = STEPT  ! Store step duration in STATEV(2)
         ELSE
   C        Retrieve the stored step duration from STATEV for other increments
            STEPT = STATEV(2)
         END IF
   
   C     update the STAFIL at the end of the step
         IF (KINC .EQ. 1) THEN
            OPEN(17, FILE=STAFIL, STATUS='UNKNOWN')
            WRITE(17,*) 'NOTREADY'
            CLOSE(17)
         END IF
   
   C     Interpolate moisture values spatially
         DO 300, I = 1, NUMVAL - 1
            IF (COORD(1) .GT. XX(I) .AND. COORD(1) .LT. XX(I+1)) THEN
               MOISTA = MOFDST(I) + (MOFDST(I+1) - MOFDST(I)) * (COORD(1) - XX(I)) / (XX(I+1) - XX(I))
               MOIEND = MOFDEN(I) + (MOFDEN(I+1) - MOFDEN(I)) * (COORD(1) - XX(I)) / (XX(I+1) - XX(I))
               GO TO 300
            ELSE
               IF (COORD(1) .LT. XX(1)) THEN
                  MOISTA = MOFDST(1)
                  MOIEND = MOFDEN(1)
                  GO TO 300
               ELSE
                  MOISTA = MOFDST(NUMVAL)
                  MOIEND = MOFDEN(NUMVAL)
                  GO TO 300
               END IF
            END IF
   300   CONTINUE
   
   C     Linearly interpolate between start and end moisture values
         MOIINT = MOISTA + (MOIEND - MOISTA) * (TIME(1) / STEPT)
   
   C     Assign the interpolated moisture value back to FIELD for this time increment
         FIELD(1) = MOIINT
   
   C     Update the state variables
         STATEV(1) = MOIINT
         END