Study On Springback During Incremental Creep Age Forming Of 7055 Aluminum Alloy Stiffened Panel

Integral panel is one of the most important parts in modern plane. It is not only the important component of the aircraft aerodynamic shape, but also the main strained component of wing and fuselage. Creep age forming is a technology developed for integral panel forming. It uses the creep feature of metal to combine the artificial aging and creep forming. However, due to the drawback of traditional age creep forming process, some problems found during the forming of integral panel with high ribs or other complex internal structures, such as wrinkling, cracking, etc.To research and develop better forming technology for integral panel, the concept of incremental creep age forming is proposed for the first time in this paper. The regular pattern is researched by finite element simulation. Incremental creep age forming is developed from the traditional direct creep age forming by absorbing the idea of multi-point incremental forming. In incremental creep age forming, the stiffened panel is fixed in the radius reduced die in turn, with less deformation but more times, the stiffened panel formed finally. By forming little every time, the ribs and internal structure can avoid damage effective. In addition, it is convenient to compensate the bringbanck. The incremental creep age forming was achieved by multi-point press mold at the beginning. But taking into account the simplification of experimental and the convenience for regular pattern researching, the molds which radius reduced by step are used.In this paper, the ageing strengthening aluminum alloy with ribs is studied based on ABAQUS finite element software platform. By using the creep constitutive equations in this software, the finite element analysis model of incremental creep age forming is created. In the analysis model, the forming part is exported from every stage, and then setup in the radius reduced mold for continue creep aging. Finally, the whole incremental creep age forming completed. By analyzing the springback rate and residual stress of the formed parts with maintaining other factors constant, the influence of process parameters in incremental creep age forming is systematically studied. The parameters include the times of incremental load step, time, temperature, thickness of the sheet, height of the ribs. This regular pattern may provide some useful reference for the integral panel forming.The direct creep age forming and integral creep age forming are used to form the same part. Analyzing the forming process of the both methods, by comparing the part's condition during the forming, springback rate and residual stress after the forming, find out the characteristics of both forming methods. It is proved that the incremental creep age forming could get better forming condition, avoid wrinkling effectively and get intact formed parts finally.