ABAQUS子程序VDLOAD编写实现移动车辆荷载

ABAQUS子程序VDLOAD可以用于实现移动车辆荷载。具体步骤如下：

1. 定义VDLOAD子程序，包括输入参数、输出参数和子程序代码。

2. 在主程序中调用VDLOAD子程序，并将所需参数传递给子程序。

3. 在VDLOAD子程序中实现荷载的计算和施加。

下面是一个VDLOAD子程序的示例代码，实现了移动车辆荷载的施加：

      SUBROUTINE VDLOAD(U, V, A, T, SVARS, CFN, PNEWDT, &
           DTIME, KSTEP, KINC, KU, NDJAC, &
           NJAC, NPROPS, COORDS, &
           NEN, NDN, NDFCD, &
           NOUT, NDI, &
           NFIELD, FIELD, &
           NEL, NPT, LAYER, KSPT, &
           KSLAY, NRESLT, RESULT)

C     Input parameters:
C
C        U(NEN,NDFCD) - nodal displacements
C        V(NEN,NDFCD) - nodal velocities
C        A(NEN,NDFCD) - nodal accelerations
C        T - current time
C        SVARS(*) - state variables
C        CFN - contact force normalization factor
C        PNEWDT - suggested new time increment
C        DTIME - current time increment
C        KSTEP - current step number
C        KINC - current increment number
C        KU - analysis mode flag
C        NDJAC - size of Jacobian array
C        NJAC - number of rows in Jacobian array
C        NPROPS - number of material properties
C        COORDS(NEN,NDN) - nodal coordinates
C        NEN - number of nodes per element
C        NDN - number of degrees of freedom per node
C        NDFCD - number of velocity fields
C        NOUT - number of integration points
C        NDI - number of history variables
C
C     Output parameters:
C
C        NFIELD - number of solution-dependent state variables
C        FIELD(NFIELD,NOUT) - solution-dependent state variables
C        NEL - element number
C        NPT - integration point number
C        LAYER - layer number
C        KSPT - segment number
C        KSLAY - layer set number
C        NRESLT - number of fields in RESULT array
C        RESULT(NRESLT) - results array
C
C     Local variables:
C
C        RHO - vehicle density
C        L - vehicle length
C        W - vehicle width
C        H - vehicle height
C        VEL - vehicle velocity
C        ACC - vehicle acceleration
C        TIRE_SPACING - spacing between tires
C        WHEELBASE - distance between front and rear axles
C        FRONT_OVERHANG - distance from front axle to front of vehicle
C        REAR_OVERHANG - distance from rear axle to rear of vehicle
C        X - x-coordinate of integration point
C        Y - y-coordinate of integration point
C        Z - z-coordinate of integration point
C        FX - x-component of force
C        FY - y-component of force
C        FZ - z-component of force

      DIMENSION U(NEN,NDFCD), V(NEN,NDFCD), A(NEN,NDFCD), SVARS(*), &
           COORDS(NEN,NDN), FIELD(NOUT), RESULT(NRESLT)

C     Define vehicle properties
      RHO = 1000.
      L = 4.
      W = 2.
      H = 1.
      VEL = 10.
      ACC = 2.
      TIRE_SPACING = 1.
      WHEELBASE = 2.
      FRONT_OVERHANG = 1.
      REAR_OVERHANG = 1.

C     Get integration point coordinates
      X = COORDS(1,1)
      Y = COORDS(1,2)
      Z = COORDS(1,3)

C     Calculate force components
      IF (Z .LE. 0.5*H) THEN
         FX = RHO*L*W*VEL*VEL/2.
         FY = 0.
         FZ = RHO*H*VEL*ACC
      ELSEIF (Z .GE. 0.5*H+TIRE_SPACING) THEN
         FX = 0.
         FY = 0.
         FZ = 0.
      ELSE
         FX = RHO*L*W*VEL*VEL/2.
         FY = 0.
         FZ = RHO*H*VEL*ACC/2.
      ENDIF

C     Apply force to nodes
      DO I = 1, NEN
         DO J = 1, NDFCD
            U(I,J) = U(I,J) + FX/2.
            V(I,J) = V(I,J) + FY/2.
            A(I,J) = A(I,J) + FZ/2.
         ENDDO
      ENDDO

C     Set output variables
      NFIELD = 0
      NEL = 1
      NPT = 1
      LAYER = 1
      KSPT = 1
      KSLAY = 1
      NRESLT = 0

      RETURN
      END

在主程序中，可以调用VDLOAD子程序，并将所需参数传递给子程序。例如：

*STEP, INC=1000, NLGEOM=YES
*STATIC
*DLOAD
VDLOAD, 1, TIME, SVARS, 1., PNEWDT, DTIME, ISTEP, INC, &
       KU, NDJAC, NJAC, NPROPS, COORDS, NEN, NDN, NDFCD, &
       NOUT, NDI, NFIELD, FIELD, NEL, NPT, LAYER, KSPT, &
       KSLAY, NRESLT, RESULT

在此示例中，TIME变量表示当前时间，SVARS变量表示状态变量，其余参数根据需要进行设置。