PDA

View Full Version : Relationship between mass moment of inertia and second moment of area?


Fat Ryan
Jan3-11, 03:42 PM
I am trying to create a model in SimMechanics of a simple damped frame. I am very new to this software and structural dynamics as well. I have a copy of "Dynamics of Structures" 3ed by Chopra. In the textbook, the author uses the standard geometric and material properties that I am familiar with to obtain stiffnesses (modulus of elasticity, E & second moment of area, I). Simscape, however, asks for mass and inertia tensor. The latter of which has units of mass*length^2. Is there some sort of relationship between the area moment of inertia and mass moment of inertia? The reason it of importance is because I need to create this model and verify it somehow. If I replicate an example in the textbook, then obviously I'll know if I'm doing things correctly. Unfortunately, the textbook only provides area moment of inertia in it's examples.

viscousflow
Jan3-11, 06:16 PM
Sorry, the two are totally independent of each other.

Fat Ryan
Jan3-11, 06:21 PM
Sorry, the two are totally independent of each other.

hmm, does anyone know why there's a difference between the book and simscape then?

leosc
Mar23-11, 08:13 PM
Sorry, the two are totally independent of each other.

This isn't really true...

They are different, but still dependent/related to each other...
I've never found this in a book,
but one can show the relation between them by using balance of linear momentum...

The relation is the following:

Imass = \rhoarea * Iarea

where

Imass : Mass Moment of Inertia
Iarea : Area Moment of Inertia
\rhoarea : area density (kg/mē)

enigma
Mar24-11, 03:36 PM
Assuming constant density...

leosc
Mar24-11, 03:42 PM
Assuming constant density...
Yes, I forgot to mention that. Thanks!