| New Al-Li alloy profiles of asymmethic section were widely used for important trusses manufacturing of Chinese independently developed large airplane C919 in rear fuselage, which used by four roll bending forming method. Because of high strength of the materials, asymmethic section, and variable curvature of these kinds of Al-Li profiles, the traditional roll bending method is difficult to produce high quality profiles, besides, it makes low processing efficiency and high waste rate. To meet airplane's development, it's urgent to study related technology. For this reason, this paper took four roll bending of 2099-T83 Al-Li alloy 2-shaped and 2099-T3 Al-Li alloy L-shaped profiles for instance, related key technology work has been carried out.By materials' formability tests of 2099-T3 and 2099-T83 Al-Li alloy, main formability parameters and constitutive equations of two materials were obtained, bending test and simulatation of 2099-T3 and 2099-T83 Al-Li alloy sheet were carried out, analysing influence of sheet's thickness, material type, and bending displacement on bending angle of sheet after springback, these works provided basis for the following process simulation analysis.Roll bending process of 2-shaped and L-shaped profiles were analyzed from the view of mechanics, possible process problems in roll bending were analyzed. Taking the MC4P431 IAS new type numerical control roll bending machine as the object, equal curvature roll bending simulations of two kinds of profile were conducted. Firstly, influence of friction coefficient on roll bending springback of the 2-shaped and L-shaped profiles was analyzed. The less of friction between profile and rollers, the better of result in the case of material feeding wasn't affected during roll bending.Then, effects of gap between 2-shaped profile and rollers, clearance between bottom roller and 2-shaped profile in vertical direction, displacement in X direction of left and right rollers were discussed on oblique bending of 2-shaped profile during roll bending; Effect of different clamping displacement of upper and lower rollers on oblique bending of L-shaped profile was researched. Therefore, oblique bending control methods of two kinds of profiles were obtained, the best roll bending parameters of two kinds of profiles are determined. At last, based on the best roll bending process parameters, equal curvature roll bending simulations of two kinds of profile were finished under the different uplifting amounts of left and right rollers, roll bending forming and springback laws of two kinds of profiles were obtained.According to the best roll bending process parameters and rolling bending forming law of two kinds of profiles, rollers of 2-shaped and L-shaped profiles in roll bending were designed and manufactured, variable curvature roll bending simulations and process verification experiments of them were carried out by equal curvature piecewise roll bending method, experimental results were in good agreement with the simulation results. After roll bending experiments, degree of longitudinal outline and oblique bending, sectional dimension errors of two kinds of variable curvature profiles are analyzed, and the results show that they meet the design requirements.The results obtained in this paper were shown as follows: 1. oblique bending control methods of 2-shaped and L-shaped profiles were presented. 2. Rolling bending forming law of two kinds of profiles were summarized. 3. Equal curvature piecewise roll bending method was presented to solve processing scheme of variable curvature profiles. In this paper, manufactures of 2-shaped and L-shaped variable curvature profiles have been completed, the presented work has solved roll bending process problem of C919 aircraft's profile. The research results have been successfully applied to production of C919 aircraft's profiles, and have improved level of Chinese roll bending working. |
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