aircraft loads and load path question 2

[nolovenodie]

Hello everyone, i'm a new stresser just started in in the aircraft industry.

I would like some guidance on where to find resource that can explain to me how external loads on an aircraft produces internal loads that we use to analyze a piece of structure on the plane (like skin shear loads, stringers axial loads, etc...)

For some reason, shear loads and shear flow is so confusing to me because I don't know "Where" or "How" they came about?

Thanks so much in advance.

 

[SWComposites]

Airframe Stress Analysis and Sizing, Niu
Aircraft Structures, Perry
Synthesis of Subsonic Airplane Design, Torenbeek

 

[nolovenodie]

Thank you so much, SWComposites...I have scanned through the first 2 books..I sense these two books go into analysis details but did not talk into detail about how the loads come about. (maybe I didn't read it careful enough)

I will also check out Synthesis of Subsonic Airplane Design.

Thanks again

 

[SWComposites]

Aircraft Loading and Structural Layout, Howe

http://www.aiaa.org/content.cfm?pageid=360&id=1186

Structural Loads Analysis for Commercial Transport Aircraft

http://www.aiaa.org/content.cfm?pageid=360&id=280

 

[rb1957]

Bruhn "Analysis of Flight Vehicle Structures"
Raymer is another good overview book (like Torenbeek)

maybe we're being guuided by "i'm a new stresser ..." and think your interested in airplane internal loads ? maybe you're looking for an aerodynamics book ?

 

[nolovenodie]

thanks everyone...i will check out those resources....

rb...

Yes i'm referring to airframe internal loads for stress analysis...I just wanted to get a really clear understanding how aircraft external loads (maneuver load, cargo load, cabin pressure loads) ...how it translate to the internal loads that I will use to do analysis.....

I think what lead me to this question is because i'm still confused about the concept of shear flow in the skin of fuselage/wing...could any body point me to any diagrams or explanation for this?

Thanks in advance...

 

[inertia4u]

nolovenodie:

Another option is for you to try finding an experience engineer and make him/her your mentor. Keep pestering your mentor until you get a grasp of it. If you still don't get it, ask around. One thing I've found over the years is that if the engineer knows "it" and "understands it", he/she can explain it clearly. Remember that you are at the early stages of your craft, so ask the experienced ones.

Let us know if you are still having problems. And remember, what you learned is school still applies!

NERT
inertia4u(at)gmail
drop me a line



-----
Nert

 

[nolovenodie]

thanks so much for the advise Nert..

 

[rb1957]

a bit of an oddly specific region to be unsure of ...

the wing/fuse joint loads balance the wing loads (and oddly enough the fusleage loads). it's easy to see in a determinate struted wing configuration, much harder to see in a redundant built-in wing (like on most large jets). part of the confusion is the complexity of the joint makes some of the redundancies penalising (ie adding to the load rather than reacting it).

but these complicated, redundant joints are everywhere in a plane, maybe this is just the part of the plane you're looking at now ?

 

[KirbyWan]

After reading your post I was thinking you needed to focus on practicing the fine art of free body diagrams to be able to understand how pressure loads and fluid friction loads stress a skin and how that stress gets transfered into the supporting structure. I would guess you will need to FBD each case from straight and level flight to maximum and minimum G loads as the air flow over the surfaces can different in each case. rb1957 does make a good point that because most of these components are designed with redundant load paths they are overdefined which is much more difficult to solve analytically.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[Andries]

One way of visualising the internal - external loads situation is to consider a simple cantilevered beam with two spar caps (booms)and a thin web. A standard approximation is to assume that the caps carry the bending moments and the shear web the shear. This approximates a wing spar that has to transfer the external (aerodynamic) load to the wing attachments. A load path can be defined as the assemblage of structural elements that "transfer" a load from its point of application to the point(s) of reaction.
In general the internal loads will follow the shortest load path which is usually the stiffest. The stiffest load path also carries the biggest share of the load. Any change in direction of a load path will induce high local stresses due to bending, that is why the elements constituting a load path should be as direct as possible.

Regards

Andries