• Welcome aboard HomebuiltAirplanes.com, your destination for connecting with a thriving community of more than 10,000 active members, all passionate about home-built aviation. Dive into our comprehensive repository of knowledge, exchange technical insights, arrange get-togethers, and trade aircrafts/parts with like-minded enthusiasts. Unearth a wide-ranging collection of general and kit plane aviation subjects, enriched with engaging imagery, in-depth technical manuals, and rare archives.

    For a nominal fee of $99.99/year or $12.99/month, you can immerse yourself in this dynamic community and unparalleled treasure-trove of aviation knowledge.

    Embark on your journey now!

    Click Here to Become a Premium Member and Experience Homebuilt Airplanes to the Fullest!

Beam Theory - Billski can you elaborate here?

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Fenix

Well-Known Member
Supporting Member
Joined
Dec 25, 2020
Messages
90
I'm reading through Beam Theory and finding it an excellent description an ultra novice can follow.
But then I came to this and it has me held up:

*******

Bending – if we take a little section of the beam and put a bending moment on each end of the section, the little section of beam becomes curved (a tinyamount) and stresses build up across the section in relation to how far we are from the neutral axis. And because plane cross sections remain plane, even in the deflected beam, the stresses are linear with distance from the neutral axis. And so the resistance to bending goes with E (we know that strain and stress are related linearly byYoung’s Modulus, E) and with I, the Second Area Moment of Inertia of the section. So now we have: Bending stiffness at any point along a beam is EI.

What else? Well, if we know the moment bending the beam, we can also calculate the axial stresses any place up and down along the cross section. Axial stress sigma is M*z/I where the moment is M, z is how far up or down we are from the neutral plane, and I is the Second Area Moment of Inertia ofthe section. Highest stress is at the farthest point on the cross section from neutral axis.


*******

I'm good up to "because plane sections remain plane" Can someone maybe state that in a different phrase or further explain please?
I think I follow "stresses are linear with distance from neutral" - it simply means the increase in stress is a linear function as you move outward (from neutral axis) and not an exponential function??

Next I will be asking what are "E" and "I" and "second moment of inertia". I found second moment of inertia on Google but the description seems to be written to people who already know what it is.

Perhaps I'm too inexperienced for your thread? Sorry.
 
Back
Top