Numerical damping effect

[hnng]

Hi,

I am trying to generate an impulse response of a simply supported beam, with a spring element at the end. A very crude picture of the problem is shown below. The - part is the beam and /\ part is the spring. The impulse force is applied at the middle, in vertical downward direction.

.----------./\/\/\|

The response of the analysis is decaying even though there is no damping in the system. The solution phase code is given below, and the complete code is attached to the posting. The damping in the response is hence numerical. Can anyone help me to setup the simulation such that the numerical damping can be minimized.

============================
/SOLU ! Enter solution phase
outres,all,all
ANTYPE, TRANS ! Transient analysis
TRNOPT,FULL

deltim,0.001

TIME,0.001
KBC,1 ! step apply load
F,25,FY,0 ! Load right end
SOLVE

TIME,0.01 ! Sets time to 1 second
KBC,1 ! step apply load
F,25,FY,-1000 ! Load right end
SOLVE

TIME,3 ! Sets time to 1 second
KBC,1 ! step apply load
F,25,FY,0 ! Load right end
SOLVE
FINISH

 

[hacksaw]

http://www.see.ed.ac.uk/.../ANSYSstuff/ANSYS Materials/ANSYS_Workbench

-fea_concepts.pdf


good luck, it is covered

 

[hacksaw]

oops wrong link

http://www.cadfamily.com/download/CAE/FEA/Ansys Structural Analysis Guide.pdf

or

http://www1.ansys.com/customer/content/documentation/130/ans_str.pdf

 

[hnng]

Thanks for posting the link... I am following the document. If possible can you point to the section which covers my query. Appreciate your help.

 

[hacksaw]

ANTYPE,TRANS
TRNOPT,FULL

TINTP,0.3 ! 30% DAMPING

what happens when TINTP is set to 0.0