Research On Stretch Bending Process For Asymmetrical Cross-section Extrusions

The parts of stretch bending are widely used for the planes frame components due to their highdimensional accuracy as well as good surface quality. With the improvement of aircraft structurecomplexity, asymmetrical cross section extrusions become the difficulty in the plane framecomponent manufacturing due to their uneven cross section deformation and difficult to controldimension precision. It is important to extend the service life of the aircraft to confirm reasonably thiskind of extrusions’ technological parameters and accurately predict springback amount and crosssection distortion.This paper adopted the method of numerical simulation combined with experimental verificationto research the stretch bending process of asymmetrical T-section and L-section aluminum extrusionswith concave. The constitutive relation of the7075-O was obtained by performing the tensile test.According to the working principles of A-7B CNC Section Stretch Wrap Forming Machine, the finiteelement model of displacement control was established and the loading trajectory was determined;The influence rules of different factors on the springback and distortion were studied by analyzing theresults of numerical simulation. The results show that: The loading method of firstly pre-stretching,secondly bending, lastly post-stretching is a more appropriate way, because the springback amountafter unloading is small; With the increment of pre-stretching or post-stretching, the springbackamount has a tendency to decrease, but cross section distortion is showed a trend of increase, and thedistortion near the origin is bigger; The increased amount of pre-stretching is helpful to eliminate thewrinkling, extrusions will have the risk of cracking, if the post-stretching is too large; As the frictioncoefficient increases, the springback amount increases slightly.According to the results after the simulation, it was constantly adjusting the parameters of stretchbending and the size of mold shape until to determine the proper stretch bending parameters. Thenumerical simulation was verified the accuracy and feasibility by testing the stretch bending of bigcurvature L-section extrusions with concave.