Relationship Between Young's Modulus and Section Modulus.
Relationship Between Young's Modulus and Section Modulus.
(OP)
I am trying to find a relationship between the Young's Modulus and the Section Modulus.
I am currently comparing different structural shapes made out of different materials and was wondering if there was a relationship between the two moduli (?) which would allow me to compare different shapes with different materials.
To be more specific, I am comparing steel structural shapes with aluminum ones trying to design a lighter, stronger/stiffer profile for us to use.
If anyone can help me with this or point me in the right direction I would greatly appreciate it. Thank you.
I am currently comparing different structural shapes made out of different materials and was wondering if there was a relationship between the two moduli (?) which would allow me to compare different shapes with different materials.
To be more specific, I am comparing steel structural shapes with aluminum ones trying to design a lighter, stronger/stiffer profile for us to use.
If anyone can help me with this or point me in the right direction I would greatly appreciate it. Thank you.





RE: Relationship Between Young's Modulus and Section Modulus.
Regards,
Mike
RE: Relationship Between Young's Modulus and Section Modulus.
Are you talking about Section Modulus, or Shear Modulus?
RE: Relationship Between Young's Modulus and Section Modulus.
Regards,
Mike
RE: Relationship Between Young's Modulus and Section Modulus.
I'm talking about Section Modulus. S = I/c.
I didn't think there was a relationship but a coworker brought it up. He mentioned he remembered working on a project a long time ago dealing with this.
He told me to look at composites and that he believed there was a relationship between the two.
RE: Relationship Between Young's Modulus and Section Modulus.
Thanks for the suggestion. Just thought I'd ask.
RE: Relationship Between Young's Modulus and Section Modulus.
Your co-worker must not understand mechanics. Or maybe he is thinking section modulus and strain...
Here is something relating the 'related' modulus's
http:/
Fe
RE: Relationship Between Young's Modulus and Section Modulus.
I was just wondering if anyone else had heard of that. He is one of our senior engineers who deals with FEA so I thought maybe he knew something I didn't.
RE: Relationship Between Young's Modulus and Section Modulus.
allowable strain = 0.2%
bending stress = Mc/I
bending strain = Mc/(IE)
so allowable moment = 0.002*E*(I/c) ?
RE: Relationship Between Young's Modulus and Section Modulus.
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.
RE: Relationship Between Young's Modulus and Section Modulus.
RE: Relationship Between Young's Modulus and Section Modulus.
RE: Relationship Between Young's Modulus and Section Modulus.
As an example, once upon a time, I worked on a flight simulator, where extreme stiffness was a primary design criterion. I designed the structure as a truss of 5x5x5/16 steel tube. The Chairman asked me why not aluminum. I replied that I could do the same structure at the same weight from 4x4 aluminum bar, but it was much more difficult to get full strength joints in that material.
Aluminum structurals are extruded, not rolled, so there are limits on how big your profile can get to compensate for the reduced E. At the time I did the FS, 40-ish years ago, the biggest extrusion press in the world was in Arkansas, and could handle any shape that would fit in a 13" circle. Because extruded aluminum comes out annealed, it's possible to extrude shapes in a curled form and then unwrap them before heat treat, but there are limits to that. I think there's a bigger press now, but I don't know who owns it or what the minimum run is (5000 lb, one stroke, for the one in Arkansas).
You have a really interesting problem there, but it's not going to yield nicely to just one or two equations.
Mike Halloran
Pembroke Pines, FL, USA
RE: Relationship Between Young's Modulus and Section Modulus.
Anyway, what we needed to do was design the profiles so as to be as 'stiff' as possible yet still fit into the space we had to work in and yet still get something which we could fabricate and still meet the sanitary rules, which involved more than just the materials used. BTW, if anyone has every tried to do these sorts of calculations using a mechanical 'planimeter' working with 2D drawings of proposed profiles, you'll appreciate why when we installed our first CAD system a couple of years later and I discovered that there was a built-in tool which would do this for me virtually automatically. All I had to do was draw the profile and the system would give me all the 2D Section properties virtually in seconds, I was hooked. I could do a week's worth of work in a single afternoon, which included producing the final purchasing drawings without having to beg for some detailer's time from the drafting pool.
BTW, for those of you who've never had the joy of doing section property calculations prior to the advent of CAD, this planimeter looked very much like the one we had in our office (and they were NOT cheap, costing several hundred dollars each and this was back in the early 70's):
For information about how they worked, go to:
http://en.wikipedia.org/wiki/Planimeter
http://whistleralley.com/planimeter/planimeter.htm
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.
RE: Relationship Between Young's Modulus and Section Modulus.
Be very careful welding aluminum and pay attention to fatigue strength of welds.
RE: Relationship Between Young's Modulus and Section Modulus.
Old Section Modulus is 324048.
Mike McCann
MMC Engineering
RE: Relationship Between Young's Modulus and Section Modulus.
RE: Relationship Between Young's Modulus and Section Modulus.
maybe furlongs/fortnight
RE: Relationship Between Young's Modulus and Section Modulus.
Have you ever seen one of my demos? When I'm asked whether the Siemens NX CAD software can utilize customized units, the example I always use is 'Furlongs/Fortnight' in a Velocity calculation
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.
RE: Relationship Between Young's Modulus and Section Modulus.
RE: Relationship Between Young's Modulus and Section Modulus.