*HEADING
1D TRANSIENT WAVE PROPAGATION IN AN ACOUSTIC MEDIUM WITH PRESCRIBED ACCEL
IN ABAQUS/EXPLICIT [AC3D6];
**
** C = root (K/rho)= 343.05 m/s   K=bulk mod, 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
** 
*PREPRINT,ECHO=NO,HISTORY=NO,MODEL=NO
*NODE, Nset=ODB_NSET
    1, 0,
  101, 1,
 1001, 0, 1e-2
 1101, 1, 1e-2
 1501, 0, 1e-2, -1e-2
 1601, 1, 1e-2, -1e-2
 2501, 0, 0, -1e-2
 2601, 1, 0, -1e-2
*NGEN,NSET=CHANNEL_NODES
    1,101
 1001,1101
 1501,1601
 2501,2601
*NSET,NSET=SAMPLE_NODES,GENERATE
 1,101
*NSET,NSET=NALL
ODB_NSET, CHANNEL_NODES, SAMPLE_NODES
*NODE,NSET=LOAD
10001, 0,
10002, 0, 1e-2
10003, 0, 1e-2, -1e-2
10004, 0, 0, -1e-2
10005, -0.1e-2,
10006, -0.1e-2, 1e-2
10007, -0.1e-2, 1e-2, -1e-2
10008, -0.1e-2, 0, -1e-2
*ELEMENT,TYPE=AC3D6
 1,1,1002,2,2501,1502,2502
 2,1,1001,1002,2501,1501,1502
*ELGEN,ELSET=CHANNEL
 1,100,1,2
 2,100,1,2
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
*surface,NAME=NRS
 199,S4
**
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
*ELEMENT,TYPE=C3D8R,ELSET=LOAD
500,10001,10004,10008,10005,10002,10003,10007,10006
*SOLID SECTION,MATERIAL=MAT1,ELSET=LOAD
*MATERIAL,NAME=MAT1
*ELASTIC
 180E2,0.333333
*DENSITY
 76.70,
**
*********************************
*SURFACE,TYPE=ELEMENT,NAME=SECONDARY
2,S3
*SURFACE,TYPE=ELEMENT,NAME=MAIN
500,S3
*TIE,NAME=COUPLING
SECONDARY,MAIN
********************
*NSET, NSET=QA_TEST
ODB_NSET
**
*STEP
*DYNAMIC,EXPLICIT
,.0036
** Define nonreflective boundary at x=1
*IMPEDANCE
 199,I4,
**
** Prescribe volume acceleration a0=1.
** Acceleration of interface element specified.
** In order to run single precision, the reference
** magnitude is increased to 1000.
**
*BOUNDARY,TYPE=ACCELERATION
LOAD,1,1,1.0E3
**
*OUTPUT,FIELD,NUMBER INTERVAL=1
*NODE OUTPUT
POR
*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,1,1,1.0E3
**
*ENDSTEP