Fuselage Expansion due to Pressurization
Fuselage Expansion due to Pressurization
(OP)
I am about to set up a model the fuselage cross section of a 767 to determine the expansion between the passenger floor and the crown of the aircraft under a 9.1 psi pressure.
Does anyone know roughly what sort of magnitude of expansion I should get so I can be confident that my model is correct?
Our problem is that we have an interior panel spanning from the passenger floor to crown (but not attached on the sides) that has to react some vertical loads in the crash condition, but because the radial expansion joints (to prevent loading due to pressurization) at the ceiling of the aircraft the vertical loads can only be transferred to the floor.
This configuration is showing that the panel will buckle and we are considering limiting the travel of the crown expansion joint so that in the crash case when the panel buckles (and has large displacement) it will then have a load path in tension to the crown. Note this load path is only required in the crash conditions.
We are looking at a few other options but I would be interested to know if this sort of feature has been used by other people in the past.
Does anyone know roughly what sort of magnitude of expansion I should get so I can be confident that my model is correct?
Our problem is that we have an interior panel spanning from the passenger floor to crown (but not attached on the sides) that has to react some vertical loads in the crash condition, but because the radial expansion joints (to prevent loading due to pressurization) at the ceiling of the aircraft the vertical loads can only be transferred to the floor.
This configuration is showing that the panel will buckle and we are considering limiting the travel of the crown expansion joint so that in the crash case when the panel buckles (and has large displacement) it will then have a load path in tension to the crown. Note this load path is only required in the crash conditions.
We are looking at a few other options but I would be interested to know if this sort of feature has been used by other people in the past.





RE: Fuselage Expansion due to Pressurization
RE: Fuselage Expansion due to Pressurization
RE: Fuselage Expansion due to Pressurization
i'd done similar models ... get a cyclinder working, then mess it up with stringers, frames, dblrs, doors, longerons, etc !
RE: Fuselage Expansion due to Pressurization
It is always good to do a hand calc to get a feel for your FE results. There is a good chapter on stress and deflection analysis of pressurised fuselages in the book "Introdution to the Theory of Aircraft Structures" by D. Williams. This is an old book (1960), long out of print, but good for classical methods. There is also a NACA report by Flugge on this topic.
Regards
Andries
RE: Fuselage Expansion due to Pressurization
GBor...what about decompression?
I agree with Andries...hand calculation first. Further, I'm not sure FEA is really necessary for this problem.
RE: Fuselage Expansion due to Pressurization
RE: Fuselage Expansion due to Pressurization
9.1 psi is an overpressure relief valve lift for the 767...not decompression.
RE: Fuselage Expansion due to Pressurization
The FEM gave me a differential deflection between the crown and the passenger floor of 0.17 inches.
There was some deflection of the passenger floor downwards (appears to be due to the post being pulled downwards due to the lower fuselage expansion and the SOB attachment to the floor essentially remaining in the same vertical position) which pushed the total deflection above the 0.15 inches calculated by RPstress (nice work - you got a star from me).
Thanks :)
RE: Fuselage Expansion due to Pressurization