3D Connexion Version 6.6

*MODAL DAMPING

analysis,” Section 6.3.11 of the ABAQUS Analysis User’s Manual). The value of the damping

constant, s, that multiplies the internal forces is entered on the data line.

Optional parameter:

DEFINITION

Set DEFINITION=MODE NUMBERS (default) to indicate t hat the damping values are given for

thespeciﬁedmodenumbers.

Set DEFINITION=FREQUENCY RANGE to indicate that the damping values are given for

the speciﬁed frequency ranges. Frequencyra nges can be discontinuous.

Ifbo th the *MODALDAMPING and *SELECT EIGENMODES options are used in the same

step, the DEFINITION parameter must be set equal to the same va lue in both options.

Data lines to deﬁne a fraction of criticaldamping by specifying mode numbers (MODAL=DIRECT

and DEFINITION=MODE NUMBERS):

First line:

1. Mode number of the lowest mode of a range.

2. 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.)

3. 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(RAYLEIGH and

DEFINITION=MODE NUMBERS):

First line:

1. Mode number of the lowest mode of a range.

2. 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.)

3. Massproportional damping, .

4. Stiffness proportional damping, .

Repeat this data line as often as necessary to deﬁne modal damping for different modes.

Data lines to deﬁne composite modal damping (MODAL=COMPOSITE):

First line:

1. Mode number of the lowest mode of a range.

2. 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.)

Repeat this data line as often as necessary to deﬁne modal damping for different modes.

13.10–2

ABAQUS Version 6.1 Module: ID:

Printed on: