Product: Abaqus/Explicit
User subroutine VDISP:
can be used to prescribe translational and rotational boundary conditions;
is called for all degrees of freedom listed in a user subroutine–defined boundary condition;
defines the magnitudes of the specified type of the associated boundary condition; and
can be called for blocks of nodes for which the boundary conditions are defined in the subroutine.
At the beginning of a step user subroutine VDISP is called twice to establish all required initial conditions.
The first call to user subroutine VDISP is made to establish the startup mean velocity, which is indicated by the passing of a step time value of 
into the subroutine, where 
is the current time increment. If displacement is prescribed, the returned variable, rval, corresponds to the displacement at . In this case rval should be set equal to 
, where 
, 
and 
are the initial displacement, velocity, and acceleration, respectively. If velocity is prescribed, the returned variable corresponds to the mean velocity at 
. In this case rval should be set equal to 
. If acceleration is prescribed, the returned variable corresponds to the acceleration at . In this case rval should be set equal to 
. The initial displacement and velocity are passed into the user subroutine in the arrays u and v, respectively.
The second call to user subroutine VDISP is made to establish the initial acceleration, which is indicated by the passing of a step time value of zero into the subroutine. If displacement is prescribed, the returned variable should be set equal to the displacement at . If velocity is prescribed, the returned variable should be set equal to the mean velocity at 
. If acceleration is prescribed, the returned variable should be set equal to the acceleration at zero step time.
During time incrementation user subroutine VDISP is called once for each increment to establish all required prescribed conditions.
If displacement is prescribed, the returned variable should be set equal to the displacement at stepTime+dtNext, where stepTime is the step time and dtNext is the next time increment. If velocity is prescribed, the returned variable should be set equal to the mean velocity at stepTime+dtNext/2. If acceleration is prescribed, the returned variable should be set equal to the acceleration at stepTime.
subroutine vdisp(
c Read only variables -
1 nblock, nDof, nCoord, kstep, kinc,
2 stepTime, totalTime, dtNext, dt,
3 cbname, jBCType, jDof, jNodeUid, amp,
4 coordNp, u, v, a, rf, rmass, rotaryI,
c Write only variable -
5 rval )
c
include 'vaba_param.inc'
c
character*80 cbname
dimension jDof(nDof), jNodeUid(nblock),
1 amp(nblock), coordNp(nCoord,nblock),
2 u(nDof,nblock), v(nDof,nblock), a(nDof,nblock),
3 rf(nDof,nblock), rmass(nblock), rotaryI(3,3,nblock),
4 rval(nDof,nblock)
c
do 100 k = 1, nblock
do 100 j = 1, nDof
if( jDof(j) .gt. 0 ) then
user coding to define rval(j, k)
end if
100 continue
c
return
endrval(nDof, nblock)
Values of the prescribed variable for degrees of freedom 1–6 (translation and rotation) at the nodes. The variable can be displacement, velocity, or acceleration, depending on the type specified in the associated boundary condition. The variable type is indicated by jBCType.
nblock
Number of nodal points to be processed in this call to VDISP.
nDof
Number of degrees of freedom (equals 6).
nCoord
Number of coordinate components (equals 3).
kstep
Step number.
kinc
Increment number.
stepTime
Value of time since the step began.
totalTime
Value of total time. The time at the beginning of the step is given by totalTime-stepTime.
dtNext
Next time increment size.
dt
Current time increment size.
cbname
User-specified name corresponding to the associated boundary condition.
jBCType
Indicator for type of prescribed variable: 0 for displacement, 1 for velocity, and 2 for acceleration.
jDof(nDof)
Indicator for prescribed degrees of freedom. The values given by rval(j,k) are prescribed only if jDof(j) equals 1.
jNodeUid(nblock)
Node numbers.
amp(nblock)
Amplitude values corresponding to the associated amplitude functions. These values are passed in for information only and will not contribute to the values of the prescribed variable automatically.
coordNp(nCoord, nblock)
Nodal point coordinates.
u(nDof, nblock)
Nodal point displacements at stepTime. All translations are included if one or more translational degrees of freedom are prescribed. All rotations are included if one or more rotational degrees of freedom are prescribed.
v(nDof, nblock)
Nodal point velocities at zero step time during initialization or nodal point mean velocities at stepTime-dt/2 during time incrementation. All translational velocities are included if one or more translational degrees of freedom are prescribed. All angular velocities are included if one or more rotational degrees of freedom are prescribed.
a(nDof, nblock)
Nodal point accelerations at stepTime before the boundary condition is prescribed. All translational accelerations are included if one or more translational degrees of freedom are prescribed. All angular accelerations are included if one or more rotational degrees of freedom are prescribed.
rf(nDof, nblock)
Nodal point reaction at stepTime-dt. All reaction forces are included if one or more translational degrees of freedom are prescribed. All reaction moments are included if one or more rotational degrees of freedom are prescribed.
rmass(nblock)
Nodal point masses.
rotaryI(3, 3, nblock)
Nodal point rotary inertia.
In this example a sinusoidal acceleration is imposed on the reference node of a rigid body. Nonzero initial velocity is also specified for the rigid body. User subroutine VDISP given below illustrates how the return value array is to be computed for different phases of the solution. The analysis results show that both the initial velocity and acceleration are correctly specified.
Input file
*HEADING Test VDISP with S4R element *NODE, NSET=NALL 1, 2, 2., 0. 3, 0., 2. 4, 2., 2. 9, 1., 1., 0. *ELEMENT, TYPE=S4R, ELSET=SHELL 10, 1,2,4,3 *SHELL SECTION, ELSET=SHELL, MATERIAL=ELSHELL 2.0000000e-02, 3 *MATERIAL, NAME=ELSHELL *DENSITY 7850.0, *ELASTIC 2.5000000e+11, 3.0000000e-01 *RIGID BODY, REF NODE=9, ELSET=SHELL *INITIAL CONDITIONS, Type=VELOCITY 9, 1, 0.4 *STEP *DYNAMIC, EXPLICIT, DIRECT USER CONTROL 0.01, 0.8 *BOUNDARY, USER, TYPE=ACCELERATION 9, 1 *OUTPUT,HISTORY, TIME INTERVAL=0.01, OP=NEW *NODE OUTPUT, NSET=NALL U, V, A *END STEP
User subroutine
subroutine vdisp(
c Read only variables -
* nblock, nDof, nCoord, kstep, kinc,
* stepTime, totalTime, dtNext, dt,
* cbname, jBCType, jDof, jNodeUid, amp,
* coordNp, u, v, a, rf, rmass, rotaryI,
c Write only variable -
* rval )
c
include 'vaba_param.inc'
parameter( zero = 0.d0, half = 0.5d0, one = 1.d0 )
c
character*80 cbname
dimension jDof(nDof), jNodeUid(nblock),
* amp(nblock), coordNp(nCoord,nblock),
* u(nDof,nblock), v(nDof,nblock), a(nDof,nblock),
* rf(nDof,nblock), rmass(nblock),
* rotaryI(3,3,nblock), rval(nDof,nblock)
c
c Impose acceleration
c
if( jBCType .eq. 2 ) then
c
if( stepTime .lt. zero ) then
c
c Initialization 1
c
a0 = zero
do 310 k=1, nblock
do 310 j=1, nDof
if ( jDof(j) .gt. 0 ) then
v0 = v(j,k)
rval(j,k) = v0/dt - a0*half
end if
310 continue
c
else if( stepTime .eq. zero ) then
c
c Initialization 2
c
a0 = zero
do 320 k=1, nblock
do 320 j=1, nDof
if ( jDof(j) .gt. 0 ) then
rval(j,k) = a0
end if
320 continue
c
else
c
c Time incrementation
c
amplitude = 2.0
period = 0.8
twopi = 6.2831853d0
c
do 350 k=1, nblock
do 350 j=1, nDof
if ( jDof(j) .gt. 0 ) then
rval(j,k) = amplitude*
* sin( twopi*stepTime / period )
end if
350 continue
end if
end if
c
return
end