An Equivalent Calculation Method for Press-Braking Bending Analysis of Integral Panels

Abstract

Press-braking bending is widely applied in the manufacture of aircraft integral panels because of the advantages of strong adaptability to different contours, simplicity of bending tools, short manufacturing time and low process cost. However, a simulation of bending process requires long-time calculation and consumes extensive computational resources. Considering the factors that the original model (ORM) of an integral panel is large and the press-braking bending is used only for the local area of integral panels with heavy thickness in practice, an equivalent calculation method for press-braking bending analysis of integral panels is proposed. The local bending area of an integral panel is simplified to a model of plate in this method. An exponential strengthening model is used to derive the equations of stress, strain and forming radius of the ORM and its simplified model (SPM). Meanwhile, the equivalent parameters of the SPM are determined and deduced based on three principles: that the material begin to be yielded simultaneously, the ultimate stress of the ORM is the same as that of the SPM at the same punch displacement, and the forming radii of neutral surfaces of the ORM and the SPM are identical after springback. The distribution of the stress and strain determined by finite element (FE) simulations are compared, and the FE simulations indicate that the contour curve of the SPM is in fairly good agreement with the profile of the ORM under the same bending process parameters, and the maximum difference is 13.17%. The computational efficiency is increased by more than 48%. Therefore, the proposed approach is quite suitable for industrial applications to improve the bending quality and efficiency of integral panels.

Modeling the forming process by successive local deforming for monolithic stiffened panels

“…The smooth grips (without notching) with the roughness of Ra 2.5-4 result in a solid grip without slippage between the tool and the rib and do not leave any surface defects on the rib's contact areas that would require additional processing [10]. Manufacturing regimes of the forming process for stiffened monolithic panels have not been thoroughly studied yet, and, therefore, are implemented in the industry with caution [11][12][13]. A thorough study must be carried out to fully benefit from the local deformation method and implement it in industrial manufacturing.…”