How to get the Second moment of Inertia of a shape in NX

[paulpatrick]

I have two shapes that are not exactly easy to Get the I value for.
One is like a tent shape, 5mm thick. Triangular/ hinge at the top with two flanges on either side. In the middle of the tent there is an open rib or web to give the tent more rigidity and stiffner.
I have tried the analyis body function and get a page full of results and section tool also. The Analysis tool Give loads of info. The section tool I cant seem to get it to work.

Anyhow do I pick the right value from the Information list on NX. Its the centroid one right?
I know AutoDesk do it and its pretty clear when its done.
I have another one thats like an S shape extrusion to do also.

 

[JHTH]

I'm basing this description on NX7, as that's what I've got in front of me.

First, create a set of section curves with Insert > Curve from Bodies > Section, then use Analysis > Section Inertia...

Is that what you're looking for?

Cheers,

Jon

JHTH
NX 7.0.1.7 + TC 2007

 

[cowski]

Are you looking for the center of mass and moment of inertia information or second moment of area for a particular cross section?

What goal do you have in mind?

 

[paulpatrick]

second moment of area for the particular section, to allow me to do a quick calculation.
The Information button presents alot and I dont know which is which the way its labeled.
I am after I for calculating deflections

 

[JohnRBaker]

There are two schemes, one's a bit long-in-the-tooth (ie, 'old') and one it a bit newer but it doesn't give you as much since it ONLY calculates the MAXIMUM Moment of Inertia.

Note that in either case, all you need is a simple 2D profile of you 'beam'.

So if you looking for MAXIMUM Moment of Inertia, go to...

Analysis -> Section Inertia...

...use Type 'Existing Section' and pick the profile of your 'beam' and if all you want if the 'Second Principle Moments' only toggle ON that option. After you select the profile but before you hit OK, toggle ON the 'Show Information Window' option as this will give you the best explanation of the results. There is also a nice option if you're interested in it and that's that you can have the system create for you the equivalent rectangular section which has the same area properties which can be handy if you're looking to simplify you model for analysis purposes.

As for the older function, with a misleading name of...

Analysis -> Advanced Masse Properties -> Area using Curves...

...which has the very old interface but it still works and it will provide Area Moment information both in terms of the Maximum values, but also with respect to the WCS.

Anyway, take a look and see if this gives you what you're looking for.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.com/museum/

To an Engineer, the glass is twice as big as it needs to be.