ProductsAbaqus/Standard
TypeModel data
LevelModel
Optional, mutually exclusive parameters (if no parameter is specified,
Abaqus
assumes that the modal damping coefficients are provided on the data
lines)
- STRUCTURAL
Include this parameter to select structural damping, which means that the
damping is proportional to the internal forces but opposite in direction to the
velocity.
This parameter can be used only with the
STEADY STATE DYNAMICS,
RANDOM RESPONSE, SIM-based
MODAL DYNAMIC, or
COMPLEX FREQUENCY procedures (see
Mode-based steady-state dynamic analysis,
Random response analysis,
Transient modal dynamic analysis,
and
Complex eigenvalue extraction).
The value of the damping coefficient, ,
that multiplies the internal forces is entered on the data line.
- VISCOUS
Set VISCOUS=FRACTION OF CRITICAL DAMPING to select modal damping using the damping coefficients given
in this option. The data lines specify the modal damping values to be used in
the analysis.
Set VISCOUS=RAYLEIGH to indicate that the damping for a particular mode is defined
as ,
where
and
are coefficients defined on the first data line of the option and
is the modal mass and
is the modal stiffness for mode M.
Optional parameters
- DEFINITION
Set DEFINITION=MODE NUMBERS (default) to indicate that the damping values are given for
the specified mode numbers.
Set DEFINITION=FREQUENCY RANGE to indicate that the damping values are given for the
specified frequency ranges. Frequency ranges can be discontinuous.
Data lines to define a fraction of critical damping by
specifying mode numbers (if no parameters are specified or if VISCOUS=FRACTION OF CRITICAL DAMPING and DEFINITION=MODE NUMBERS)
- First
line
Mode number of the lowest mode of a range.
Mode number of the highest mode of a range. (If this entry is left blank, it
is assumed to be the same as the previous entry so that values are being given
for one mode only.)
Fraction of critical damping, .
Repeat this data line as often as necessary to define modal
damping for different modes.
Data lines to define Rayleigh damping by specifying mode numbers
(VISCOUS=RAYLEIGH and DEFINITION=MODE NUMBERS)
- First
line
Mode number of the lowest mode of a range.
Mode number of the highest mode of a range. (If this entry is left blank, it
is assumed to be the same as the previous entry so that values are being given
for one mode only.)
Mass proportional damping, .
Stiffness proportional damping, .
Repeat this data line as often as necessary to define modal
damping for different modes.
Data lines to define structural damping by specifying mode
numbers (STRUCTURAL and DEFINITION=MODE NUMBERS)
- First
line
Mode number of the lowest mode of a range.
Mode number of the highest mode of a range. (If this entry is left blank, it
is assumed to be the same as the previous entry so that values are being given
for one mode only.)
Damping coefficient, .
Repeat this data line as often as necessary to define modal
damping for different modes.
Data lines to define a fraction of critical damping by
specifying frequency ranges (VISCOUS=FRACTION OF CRITICAL DAMPING and DEFINITION=FREQUENCY RANGE)
- First
line
Frequency value (in cycles/time).
Fraction of critical damping, .
Repeat this data line as often as necessary to define modal
damping for different frequencies.
Abaqus
interpolates linearly between frequencies and keeps the damping value constant
and equal to the closest specified value outside the frequency
range.
Data lines to define Rayleigh damping by specifying frequency
ranges (VISCOUS=RAYLEIGH and DEFINITION=FREQUENCY RANGE)
- First
line
Frequency value (in cycles/time).
Mass proportional damping, .
Stiffness proportional damping, .
Repeat this data line as often as necessary to define modal
damping for different frequencies.
Abaqus
interpolates linearly between frequencies and keeps the damping value constant
and equal to the closest specified value outside the frequency
range.
Data lines to define structural damping by specifying frequency
ranges (STRUCTURAL and DEFINITION=FREQUENCY RANGE)
- First
line
Frequency value (in cycles/time).
Damping coefficient, .
Repeat this data line as often as necessary to define modal
damping for different frequencies.
Abaqus
interpolates linearly between frequencies and keeps the damping value constant
and equal to the closest specified value outside the frequency
range.