missing section modulus

[scoopthepoop2000]

I am using IV 2016.  I have used my frame generator. Used the beam calculator to to see the section modulus of one of the members. The section modulus reads zero. What am I doing wrong?

[johnsonshiue]

Hi! It does not sound right to me. Have you selected the specific member? Does this behavior only happen to this specific frame member but not others? Could you post the files here or send them to me directly (johnson.shiue@autodesk.com)?

Thanks!

[CAD-One]

Dont mean to hi-jack this thread. But, I am looking for a solution for this. I don't want to use frame generator. How can I get a section modulus of a profile like this?

[blair]

Doesn't Autocad Mechanical still calculate this within it's FEA utility?

[CAD-One]

No, It doesn't have section modulus. But it has a modulus of elasticity.

Its a simple formula that I can calculate my self.

But not sure if I can treat my fluted profile like a round profile shown below.

[swalton]

Section Modulus is the second moment of area (moment of inertia) divided by the distance from the neutral axis of a beam to some fiber in the beam.  Most often one uses the distance to the extreme fiber on the outer edge of the beam because that is the highest stressed region. See: https://en.wikipedia.org/wiki/Section_modulus

If your tube is long enough, and it is not bent prior to loading, I think you can use the distance between the geometric center of the tube and the outermost edge.  In this case it would be 1.5".  See: https://en.wikipedia.org/wiki/Neutral_axis

Model up your tube in IV, make sure to use the obvious symmetry about the part origin.  Add a cross-section sketch and use the project cut edges to get the inner and outer parameter of the tube.  Make sure that the sketch origin is at the center of the part.  Use the Edit Coordinate System command to move it if IV puts it somewhere else (RMB on the sketch in the model browser to access this command). While in that sketch, use the Region Properties tool under the Inspect tab to find the Area Moment of Inertia for that shape. Divide the Area Moment of Inertia by 1.5" to get your section modulus.

[karthur1]

Section Modulus is equal to I/y... where I is the area moment of inertia and y is the distance to the outermost edge.  Units will be in^3. y in this case is 1.5in.

You can get the I by editing the sketch and choosing "Region Properties" on the measure panel.

This would vary if the pole is tapered from one end to the other.

[CAD-One]

Thank you for explaining swalton.