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About damping in Solid mechanics

Posted 3 déc. 2014, 20:55 UTC−5 MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 4.3 1 Reply

Wang Mingkang
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Dear all,

Hi, I have a question about the damping in Solid mechanics module.
I want to simulate a piece of metal drive by Force=F0cos(wt); So I choose frequency domain and do it.
But at beginning I didn't set any damping. It means under linear elastic material node, I didn't add any sub-node. But still I can see the damping in spectrum figure. Why? Is it because computer gives a random damping as default value?
Secondly, I want to know if I want to add a right damping in my simulation system, which type of damping I need? Rayleigh or isotropic or anisotropic?
Is there any one can help me distinguish these 3 type of damping? Which type of damping should I use in my system?

Thank you.
Mingkang
1 Reply Last Post 5 déc. 2014, 11:13 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago 5 déc. 2014, 11:13 UTC−5
Hi

damping is a delicate issue, particularly in Solid physics. Depending on the solver you might have some "light numerical damping" or just round-off's that generate small complex values.

Then read carefully the theory in the COMSOL doc about damping, as the different isotropic, anisotropic, Rayleigh ... damping all apply to different cases and study types, some can be used in the time domain, other in the frequency domain, or others again in the eigenfrequency analysis, but all do not apply everywhere. To observe this, study in detail the Equation tab when you switch from one damping to another, and be sure its set for the relevant study type

--
Good luck
Ivar
Hi damping is a delicate issue, particularly in Solid physics. Depending on the solver you might have some "light numerical damping" or just round-off's that generate small complex values. Then read carefully the theory in the COMSOL doc about damping, as the different isotropic, anisotropic, Rayleigh ... damping all apply to different cases and study types, some can be used in the time domain, other in the frequency domain, or others again in the eigenfrequency analysis, but all do not apply everywhere. To observe this, study in detail the Equation tab when you switch from one damping to another, and be sure its set for the relevant study type -- Good luck Ivar

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