*HEADING
1D TRANSIENT WAVE PROPAGATION IN AN ACOUSTIC MEDIUM WITH PRESCRIBED ACCEL 
IN ABAQUS/EXPLICIT [AC2D4R]; 
VERIFICATION PROBLEM: TRANSIENT DYNAMICS TESTS
**
** C=SQRT(K/RHO)= 343.05 M/S   K=BULK MODULUS, RHO=DENSITY.  
** ANALYTIC SOLUTION TO PRESCRIBED CONSTANT ACCELERATION OF A0 AT X=0
** 
** P(X,T) = (K*A0/C^2)*(CT - X)  FOR X < CT
**        = 0  			 FOR X > CT
** FOR EXAMPLE AT THE END OF THE SIMULATION : 
**                   P_1(0,0.0044)=1.826
**                   P_51(0.5,0.0044)=1.221
**                   P_101(1.0,0.0044)=0.616
** THE ACCELERATION IS SPECIFIED USING *BOUNDARY, TYPE=ACCELERATION
**
** SEE CH. 3.7.7 OF ABAQUS/VERIFICATION MANUAL
**
*PREPRINT,ECHO=YES,HISTORY=YES,MODEL=YES
*NODE,NSET=NALL
    1, 0,
  101, 1,
 1001, 0, 1.e-2
 1101, 1, 1.e-2
*NODE,NSET=LOAD
10001,0.0,
20001,0,1.e-2
*NGEN,NSET=NALL
    1,101
 1001,1101
*NSET,NSET=QA_TEST
1,1001,41,101,1101
*ELEMENT,TYPE=AC2D4R 
1,1,2,1002,1001
*ELGEN,ELSET=CHANNEL
1,100
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
3.0
****************************************
*surface, NAME=NRS
 100,S2
*ELEMENT,TYPE=B21,ELSET=LOAD
200,10001,20001
*BEAM SECTION,MATERIAL=MAT1,ELSET=LOAD,SECTION=RECT
 0.3,3
*MATERIAL,NAME=MAT1
*ELASTIC
 180E2,0.333333
*DENSITY
 76.70,
*****************
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
**
**
*********************************
*SURFACE,TYPE=ELEMENT,NAME=SECONDARY
1,S4
*SURFACE,TYPE=ELEMENT,NAME=MAIN
200,SPOS
*TIE,NAME=COUPLING
SECONDARY,MAIN
*******************
*STEP
*DYNAMIC,EXPLICIT
,.0036
** Define nonreflective boundary at x=1
*IMPEDANCE
100,I2
**
*BOUNDARY,TYPE=ACCELERATION
LOAD,1,1,1.0
**
*OUTPUT,FIELD,NUMBER INTERVAL=1
*NODE OUTPUT
POR
*OUTPUT,HISTORY, FREQ=1
*NODE OUTPUT, NSET=QA_TEST
POR
*ENDSTEP
*STEP
*DYNAMIC,EXPLICIT
,.0008
** Define nonreflective boundary at x=1
*IMPEDANCE,OP=NEW
*SIMPEDANCE
NRS
**
*BOUNDARY,TYPE=ACCELERATION
LOAD,1,1,1.0
**
*OUTPUT,HISTORY, FREQ=1
*NODE OUTPUT, NSET=QA_TEST
POR
*ENDSTEP