Sine Sweep Test Simulation

[elimgt]

Hi,

I would like to model a sine sweep test simulation using ABAQUS. I look at the manual, it seems I can use *STEADY STATE DYNAMICS command in abaqus and I can either use modal steady state or direct stead state. I got it work and correct for undamped system for both modal and direct steady state, but somehow when I try to perform the simulation with viscous/modal damping, I either didn't got the correct resonance frequency or the result show no different with undamped system although I have put damping ratio~30%.

The structure that I looking at is a simple cantilever case with lumped mass at the tip end.

Could anyone know what is wrong with my script? I post my script for both Direct and Modal Steady State here.

**=========================================================================================================================
Here is my script for DIRECT STEADY STATE DYNAMICS
*Heading
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**==========================================================
**Creating Column part
**==========================================================
*Part, name=FPL
*NODE
1, 0.000000, 0.000000, 0.000000
11, 0.000000e+00, 43.500000, 0.000000
*NGEN
1, 11, 1
*ELEMENT, type = B31
1, 1, 2
*ELGEN
1, 10, 1, 1
*ELSET, ELSET = FPL_EL, GENERATE
1, 10, 1
*NSET, NSET = FPL_ND, GENERATE
1, 11, 1
** DEFINE Second L section: Front to Front Post Left member
*Beam Section, elset = FPL_EL, material = steel1, lumped=NO, temperature=GRADIENTS, section=RECT
1.000000, 1.000000
*END PART
**==============================================
** ASSEMBLY PARTS
*Assembly, name = assembly
*Instance, name = FPLbot, part = FPL
*End Instance
*Nset, Nset = sup_pt, Instance=FPLbot
1
**==============================================================
**Generate Node Set for Mass 10lb assignment
*Element, type = MASS, elset=masten
101, FPLbot. 11
*Mass, elset = masten, alpha = 55.488
1.047605e-05
*END ASSEMBLY
** ===============================================================================
** Define MATERIALS properties
** ===============================================================================
*Material, name = steel1
*Density
0.000000e+00
*Elastic
29500.000000, 0.300000
** ===============================================================================
** Define BOUNDARY CONDITIONS
** ===============================================================================
*BOUNDARY
sup_pt, 1, 6
*AMPLITUDE, NAME = SINE, DEFINITION = EQUALLY SPACED, FIXED INTERVAL = 1.0, BEGIN = 1.0
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088
*STEP, NAME = SINE SWEEP
*STEADY STATE DYNAMICS, DIRECT, INTERVAL = RANGE, FREQUENCY SCALE = LOGARITHMIC
10,30,50
*BOUNDARY, TYPE=ACCELERATION, AMPLITUDE = SINE
sup_pt,1,1,1.0
*Output, field, variable=ALL
*End Step

**=========================================================================================================================
Here is my script for MODAL STEADY STATE DYNAMICS[/u]
*Heading
*Preprint, echo=NO, model=NO, history=NO, contact=NO
**==========================================================
**Creating Column part
**==========================================================
*Part, name=FPL
*NODE
1, 0.000000, 0.000000, 0.000000
11, 0.000000e+00, 43.500000, 0.000000
*NGEN
1, 11, 1
*ELEMENT, type = B31
1, 1, 2
*ELGEN
1, 10, 1, 1
*ELSET, ELSET = FPL_EL, GENERATE
1, 10, 1
*NSET, NSET = FPL_ND, GENERATE
1, 11, 1
** DEFINE Second L section: Front to Front Post Left member
*Beam Section, elset = FPL_EL, material = steel1, lumped=NO, temperature=GRADIENTS, section=RECT
1.000000, 1.000000
*END PART
**==============================================
** ASSEMBLY PARTS
*Assembly, name = assembly
*Instance, name = FPLbot, part = FPL
*End Instance
*Nset, Nset = sup_pt, Instance=FPLbot
1
**==============================================================
**Generate Node Set for Mass 10lb assignment
*Element, type = MASS, elset=masten
101, FPLbot. 11
*Mass, elset = masten
1.047605e-05
*END ASSEMBLY
** ===============================================================================
** Define MATERIALS properties
** ===============================================================================
*Material, name = steel1
*Density
0.000000e+00
*Elastic
29500.000000, 0.300000
** ===============================================================================
** Define BOUNDARY CONDITIONS
** ===============================================================================
*BOUNDARY
sup_pt, 1, 6
*AMPLITUDE, NAME = SINE, DEFINITION = EQUALLY SPACED, FIXED INTERVAL = 1.0, BEGIN = 1.0
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088, 38.6088
38.6088
** STEP: MODESHAPE
*Step, name=Frequency
*FREQUENCY
60
*Output, field, variable=ALL
*End Step
*STEP, NAME = SINE SWEEP
*STEADY STATE DYNAMICS, INTERVAL = RANGE, FREQUENCY SCALE = LOGARITHMIC
10,30,50
*BASE MOTION, DOF = 1, TYPE=ACCELERATION, AMPLITUDE = SINE
*MODAL DAMPING, MODAL = DIRECT, DEFINITION = MODE NUMBERS
1, 60, 0.3
*Output, field, variable=ALL
*End Step
**=========================================================================================================================

Thanks,
Edwin