Modal Mass, Effective Mass, etc.
Modal Mass, Effective Mass, etc.
(OP)
Hello. Thanks in advance for any help.
I'm trying to apply some of the equations from the 1987 IMAC paper by Rao. It's called "Electrodynamic Interaction Between a Resonating Structure and an Exciter."
In Section 2.1 (in case anybody has this paper), he states that m equals the modal mass, but he gives no indication how it is derived. I've calculated the modal mass for my structure using several different normalization schemes and can't get results that make any sense.
When an author uses the term "modal mass," in a paper like this, what's he talking about? Is there an unstated convention that I haven't picked up on yet?
I'm trying to apply some of the equations from the 1987 IMAC paper by Rao. It's called "Electrodynamic Interaction Between a Resonating Structure and an Exciter."
In Section 2.1 (in case anybody has this paper), he states that m equals the modal mass, but he gives no indication how it is derived. I've calculated the modal mass for my structure using several different normalization schemes and can't get results that make any sense.
When an author uses the term "modal mass," in a paper like this, what's he talking about? Is there an unstated convention that I haven't picked up on yet?





RE: Modal Mass, Effective Mass, etc.
Cheers
Greg Locock
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RE: Modal Mass, Effective Mass, etc.
100000e--I've been waiting for somebody to type that!
As for the effective mass at the interface, doesn't it still matter what normalization he used? Normalizing so that PhiTransposed*M*Phi=Identity for example?
I have Ewins and I think he calls this "effective mass," which is a unique number for a given mode and DOF. Is this the one you're typing about?
RE: Modal Mass, Effective Mass, etc.
For Mode r, at DOF j, it has units of mass and is
(mjj)r=1/(phijr)^2
RE: Modal Mass, Effective Mass, etc.
Cheers
Greg Locock
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Modal Mass, Effective Mass, etc.
RE: Modal Mass, Effective Mass, etc.
seems that Rao (don't have his paper), must be using orthonormal modes