Critical damping fraction in modal dynamics step

[yikyeh]

Hi, I am doing a simulation on vibration characteristics of a lap-shear spot welded plate using Abaqus CAE. The load is defined as an impulse force (input in tabular form). I would like to ask about the damping in the modal dynamics step. I have read through the abaqus manual. However I still have no idea which types of damping (direct modal, Rayleigh or composite modal) should I use, what value of critical damping fraction should be entered, and what range of frequencies/modes should be chosen.

Thanks for your assistance.

 

[yikyeh]

I really need someone to help me to solve my problem. Your assistance is very much appreciated. Thanks.