"DSK" wrote in message
. ..
gonefishiing wrote:
refresh my memory:
i'm looking for the section modulus for a boom section to understand
allowable bending stress.
sx= bd(squared) ?

No, IIRC it's the integral of the solid cross section area distance from
the axis. That's why triangular sections have the greatest rigidty for
their cross section area, and square sections are more rigid than oval
or round.

MEANING TO THE EXTREME OUTER FIBERS IN BOTH AXIS?

I can refer you to a pretty good text book.

but this is for rectangular sections right?
how do you calculate this for an oval section?

Personally, I don't. I look it up! But this is also not foolproof, you'd
be amazed how many mfg'rs fudge their specs (or maybe they can't do math).

YEAH BEEN THERE RECENTLY: IT IS ALSO CALLED EXPENSIVE WHEN YOU DISCOVERED
THEIR PUBLISHED ERRORS.

Hope this helps.

Fresh Breezes- Doug King

No, IIRC it's the integral of the solid cross section area distance from
the axis. That's why triangular sections have the greatest rigidty for
their cross section area, and square sections are more rigid than oval
or round.


gonefishiing wrote:
MEANING TO THE EXTREME OUTER FIBERS IN BOTH AXIS?

No, all fibers along the tension/compression axis. That's why it's an
integral.


but this is for rectangular sections right?
how do you calculate this for an oval section?

Personally, I don't. I look it up! But this is also not foolproof, you'd
be amazed how many mfg'rs fudge their specs (or maybe they can't do math).


YEAH BEEN THERE RECENTLY: IT IS ALSO CALLED EXPENSIVE WHEN YOU DISCOVERED
THEIR PUBLISHED ERRORS.

I hope nobody got hurt. This is called "letting your customers do your
failure mode testing." It's very popular with software firms, too

Regards
Doug King