Patent Document ID: 20080164372
Application ID: 11969557
Patent Flag: 0

Claim One:
1. Method of optimizing the design of stiffened panels intended for the fuselage of an aircraft ( 5 ) under load, said fuselage being divided up into a set of rings ( 1 ), each ring being decomposed into subsystems ( 2 ), each subsystem being composed of a stiffener ( 3 ) and a skin portion ( 4 ) to which said stiffener is fastened, said subsystem ( 2 ) being subjected to a combined loading of compression and shear stress, characterized in that said method comprises the following successive steps: a) the local characteristics of the ith subsystem in the initial state, corresponding to a state with no buckling, are determined; b) the initial overall characteristics of the ring are determined, namely the initial offset of its neutral bending axis ΔZ 0 , its static moment [EW] 0 and its flexural rigidity [EI] 0 are determined from the local characteristics of the ith subsystem; c) the following are determined in an iterative loop and each iteration n: the working local characteristics of the subsystem taking into account the loss of rigidity due to buckling, and the new overall characteristics of the ring, namely its offset [ΔZ 0 ] n , its flexural rigidity [EI] n and its static moment [EW] n , the convergence of the iterative loop being obtained if the new offset is below a threshold; d) the final stress distribution in the subsystem is determined; e) the safety margins are determined from the final stress distribution in the subsystem taking postbuckling into account; and f) the mass function of the subsystem is minimized while respecting the safety margins.