Numerical And Experimental Research On Variable Angle Bend-stretch Forming Of Aircraft Fuselage Extrusion Profiles

A large number of aircraft structural parts are produced from extrusion profiles,a type of which is airframe parts. Parts manufactured with extrusion profiles mayreduce its own weight without influencing the part strength. Lightweight can beachieved as a result, which is significant for aircraft manufacturing.Two typical aircraft frame parts，rear fuselage architrave part and stern partwere selected for investigation. Numerical simulations and experiments were usedfor studying forming processes of two parts. First of all, FEA models wereestablished for the simulation of bend-stretch processes of rear fuselage architravepart and stern part. Then, variation of stress and strain and wall thickness werestudied, effect of forming load to forming quality was investigated as well. It couldbe indicated that chuck tensile force is the key factor influencing two parts’ formingprocess. Besides that, there exists an optimized range for the chuck tensile force.Utilizing the optimized load, rear fuselage architrave parts with maximum thinningnot exceeding7.1%and stern parts with maximum thinning not exceeding5.6%canbe obtained, whose surface is smooth and sound, with no wrinkle appearing.The mechanical performance of aluminum alloy7075-O, which the two partsare made of, was measured through single-axis stretching test. Also, bend-stretchmolds were designed and manufactured for the use of stretch bending test of the twoparts. It could be seen from the experimental results that the secondary stretchbending’s tensile force used in the double bend-stretch method increased by50%forrear fuselage architrave part, which therefore decreased unloading spring-backeffectively and improved forming accuracy. While the blank profile plays a key rolein rear fuselage architrave parts’ angle control. As a result, it would be better topre-form the blank according to the angle of final parts. Also, the secondary stretchbending’s tensile force used in the double bend-stretch method increased by43%forstern part, which decreased unloading spring-back and improved forming accuracyas well.