This option is used to specify diagonal modal damping coefficients associated with the substructure eigenmodes. Substructure modal damping contributes to the substructure damping matrices at the substructure usage stage. This option is used in conjunction with the *SUBSTRUCTURE PROPERTY option. If this option is omitted, the element set containing the substructures for which the properties are being defined will exclude modal damping.
Product: Abaqus/Standard
Type: Model data
Level: Model
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,” Section 6.3.8 of the Abaqus Analysis User's Guide; “Random response analysis,” Section 6.3.11 of the Abaqus Analysis User's Guide; “Transient modal dynamic analysis,” Section 6.3.7 of the Abaqus Analysis User's Guide; and “Complex eigenvalue extraction,” Section 6.3.6 of the Abaqus Analysis User's Guide).
The value of the damping coefficient, , that multiplies the internal forces is entered on the data line.
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.
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.
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.
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.
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.
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.
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.
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.