*heading
 reference solution for vuel_springs_3d_freevibrotx.inp
 using cartesian + cardan connector in ABAQUS/Explicit instead of vuel
 period = 2*Pi*sqrt(ri_xx/dRotStiff_xx)=0.06283 (Analytical)
 period obtained using connector element (results from this input file)=0.062941 (measured from 17 cycles)
*parameter
**
** translation properties
dMass  = 7214.5
dStiff = 1.0521e7
dDamp  = 0.0
**rotational properties
dRotStiff_xx = 1000.0
dRotStiff_yy = 1000.0
dRotStiff_zz = 2000.0
dRotDamp = 0.0
**
ri_xx = 0.1
ri_yy = 0.2
ri_zz = 0.3
ri_xy = 0.0
ri_yz = 0.0
ri_xz = 0.0
**-------------------
*node, nset=PR
 101, 0.0, 0.0, 0.0
 102, 2.0, 0.0, 0.0
*nset, nset=qa_test_left
 101,
*nset,nset=qa_test_right
 102,
**mass is located at the second node
*element, type=mass, elset=mass
 101, 101
 102, 102
*mass, elset=mass
 <dMass>,
*element, type=rotaryi, elset=rotaryi
 201, 101
 202, 102
*rotary inertia, elset=rotaryi, orientation=orient_1
 <ri_xx>,<ri_yy>,<ri_zz>,<ri_xy>,<ri_xz>,<ri_yz>
*ORIENTATION, NAME=orient_1, DEFINITION=COORDINATES, SYSTEM=RECTANGULAR
 1.0     ,0.0       ,0.0       ,0.0       ,1.0       ,0.0    
**define connector element
*element, type=conn3d2, elset=cartesiancardan
 1, 101, 102
*connector section, elset=cartesiancardan, behavior=cb_cartesiancardan
 cartesian, cardan
 orient_1
*connector behavior, name=cb_cartesiancardan
*connector elasticity, component=1
 <dStiff>,
*connector elasticity, component=2
 <dStiff>,
*connector elasticity, component=3
 <dStiff>,
*connector elasticity, component=4
 <dRotStiff_xx>,
*connector elasticity, component=5
 <dRotStiff_yy>,
*connector elasticity, component=6
 <dRotStiff_zz>,
*boundary
 qa_test_left, 1, 6
 qa_test_right, 1, 3
 qa_test_right, 5, 6
*initial conditions, type=velocity
 qa_test_right, 4, 1.0
**-------------------------------------------
*STEP, NLGEOM=yes
*DYNAMIC, EXPLICIT, direct, scale=0.1
 1e-3,2.0
*bulk viscosity
 0.0, 0.0
*output,field,var=preselect,num=1
*output, history, freq=1
*node output, nset=PR
u,v,a,rf
*node output, nset=qa_test_left
 RF,
*node output, nset=qa_test_right
 UR, VR, AR
*energy output
*END STEP