Section properties calculation

colin_daly

Is there currently a way to use the software to calculate section properties moment of inertia, I, and section modulus, S??

andrew_troup

@colin_daly

Sorry, at present, only the Mass Moment of Inertia (which of course relates to entire parts) is available. No section properties as yet.

(For anyone who didn't know this: To access the Mass Properties dialog (which includes 'I'), select a part in the Parts list, and click the small scale icon appears in the bottom right corner of the interface

For further info, refer the Help entry on "Mass Properties Tool")

colin_daly

So I guess to get the section properties of a simple shape you could orient the part with its center of gravity at the origin, and then derive the area moment of inertia from the mass moment of inertia and density?

andrew_troup

I guess so, if you can rely on correctly interpreting the mass moment (from memory, it's given as a matrix). There was (I seem to recall) a bit of hanky panky around how well Onshape coped with studios containing parts of different densities - I think it got sorted, but just make sure to check the first few results whenever you push into a new scenario.

charlotte_moore

Hi Colin, 

With your question,

"Is there currently a way to use the software to calculate section properties moment of inertia, I, and section modulus, S??"

Yes, there is, I found this moment of inertia calculator and it's free though so you can have a look and try out. There's also one from autodesk you can check it from https://www.autodesk.com/education/free-software/featured. 

Both resources/software are useful in calculating moment of inertia. 

Good luck!

BulletEngineering

If you cut a slice of thickness "t" of the section you are interested in, there is a simple conversion from mass moment of inertia "M" to the second moment of area "I"

I = M/(t*density)

Please ensure that the units of length, mass, and density match!

*this only applies to sections that have a constant density and are prismatic, i.e. can theoretically be extruded from a single sketch along one line.

Jasper_Beekmann

Is there already an improvement request for this? The standard online calculators of course can't help me with my own designed profile.

NeilCooke

@Jasper_Beekmann    https://forum.onshape.com/discussion/comment/41979