I constructed a simple SDOF model, using a cube mass (C3D8) , SPRINGA and DASHPOTA elements. The spring and dashpot were in parallel and shared same nodes. A vertical CLOAD force was applied to cube. All DOF were restrained so the model only moved in Z-dir.
The plot of the displacement of the cube looks right but noisy. Is this to be expected as i cant see where i went wrong?
*NODE
1,0,0,1
2,0.7071067811865,0,1.707106781187
3,0.2071067811865,0.7071067811865,2.207106781187
4,-0.5,0.7071067811865,1.5
5,-0.5,-0.7071067811865,1.5
6,0.2071067811865,-0.7071067811865,2.207106781187
7,-0.2928932188135,8.659274570719E-17,2.707106781187
8,-1,8.659274570719E-17,2
9,0,0,0
*ELEMENT,TYPE=C3D8
1,1,2,3,4,5,6,7,8
*ELEMENT,TYPE=SPRINGA
2,9,1
*ELEMENT,TYPE=DASHPOTA
3,9,1
*ELSET,ELSET=Element_Selection
1
2
*ELSET,ELSET=MASS
1
*ELSET,ELSET=SPRING
2
*ELSET,ELSET=Damper
3
*MATERIAL,NAME=Material
*ELASTIC,TYPE=ISOTROPIC
210000000000,0.3
*DENSITY
7850
*SOLID SECTION,ELSET=MASS,MATERIAL=Material
*SPRING,ELSET=SPRING
3.600000000000E+007
*DASHPOT,ELSET=Damper
6000
*BOUNDARY
1,2,0
1,1,0
2,2,0
2,1,0
3,2,0
3,1,0
4,2,0
4,1,0
5,2,0
5,1,0
6,2,0
6,1,0
7,2,0
7,1,0
8,2,0
8,1,0
9,1,0
9,2,0
9,3,0
*STEP
*FREQUENCY,STORAGE=YES
1
*END STEP
*STEP
*STEADY STATE DYNAMICS, HARMONIC = YES
10,12,300
*CLOAD
1,3,100000
*NODE FILE
U
*END STEP