Learning Forum

[BlueBird Cui-Cui]

Hello all,

I have a model with COMBIN14 spring elements for which a loss factor is defined. When I make a modal analysis including damping, the damped frequency values are identical to those frequencies got obtained from undamped modal analysis.
It seems that the damping matrix [C] doesn't include the loss factor for spring elements, right ?

Thank you for your support.

 

[dlooman]

The term loss factor isn't used to describe any of the types of damping for COMBIN14, which are the real constants cv1 and cv2 and the material properties betd, dmpr and dmps.  These types of damping should all have affected the damped natural frequency, except possibly dmpr, based on Table 1.3 in the Structural Analysis Guide.  The input below tests a large value of the material property betd on the damped natural frequency.

/prep7
et,1,14
r,1,10000
mp,betd,1,.01

et,2,21,,,2
r,2,1

n,1
n,2,1
e,1,2

type,2
real,2
mat,2
e,2

d,1,all
d,2,uy
d,2,uz

fini

/solu
antyp,modal
modop,damp,2
mxpand,2,,,yes
solve
fini