about introduction of damping when UMAT applied

[Yuande Zhou]

Hi all,
I have written a UMAT for the modeling of softeing constitutive
relationship for the tensile cracked concrete. and the UMAT applies
well in the static calculation. Now I try to put it into dynamic
simulations, and it works too. But I found that the consideration
of Rayleigh damping is limited when UMAT is used. When the Beta item
of the material damping is inserted into the *damping assignment,
the following error message is given:
***ERROR: A MATERIAL PROPERTY THAT IS NOT ALLOWEDWITH A USER
MATERIAL HAS BEEN SPECIFIED

No error message comes out when only Alpha item is used. So I
want to ask how to consider the stiffness proportional damping
in this case.
Looking forward to your suggestions.
Thanks in advance.

**************
Yuande Zhou
Ph.D student
Tsinghua Univ.
**************



------------------------ Yahoo! Groups Sponsor ---------------------~-->
ReplayTV: CNet Ranked #1 over Tivo!
Instant Replay & Pause live TV.
Special Sale: 50% off!
http://us.click.yahoo.com/G93ZAD/.5qGAA/ySSFAA/PMYolB/TM
---------------------------------------------------------------------~->