Learning Forum

[Maryam Tabbakhh]

Hi,

I have three parts that I wanted to define different Rayliegh damping for each part. I calculate The coefficeint by a formulation where I need two tiers for Period (T1 and T2): 

 set xDamp1 0.15;                    # damping ratio calculated using q factor in SW4: ξ=1/2qs
 set T1 1.0;
 set T2 0.1;

 set pi 3.141593;
 set w1 [expr 2*$pi/$T1];
 set w2 [expr 2*$pi/$T2];
alfa  [expr 1*$xDamp1*(2*$w1*$w2)/($w1+$w2)];    
 beta [expr 1*2.0*$xDamp1/($w1+$w2)];  

 

Should I just calculate the alpha and beta for each part and assign it and LSDYNA will calculate Rayleigh damping by itself?

 

Thanks               

[Ashish Khemka]

Hi Maryam,

Please refer to the following link:

Damping — Welcome to the LS-DYNA support site

Regards,

Ashish Khemka

[Maryam Tabbakhh]

Dear Amish,

 

thank you very much for your response. But it is not clear for me that is there any specific option for Rayleigh damping or we should define mass damping and stiffness damping separately to get the Rayleigh Damping? 

thanks 

[Armin_A]

 

Hi Maryam,

Could you let us know which keyword card you use to define damping in LS-DYNA?

 

[Maryam Tabbakhh]

*DAMPING_PART_STIFFNESS

 AND 

*DAMPING_PART_MASS

[Armin_A]

For *DAMPING_PART_STIFFNESS, you directly input the Rayleigh damping (COEF), please see the screen-shot below from the LS-DYNA R11 keyword manual:

[Maryam Tabbakhh]

Thank you very much!