Research On The Quality Control Of Three Dimensional Multi-point Flexible Stretch-bending Forming Parts For Aluminum Alloy Profile

Traditional profile stretch-bending cannot be used to form three dimensional parts at one time,so it can not meet the complex or aesthetic requirements of the current industry.Three dimensional multi-point flexible stretch-bending forming is a new type of flexible stretch-bending forming technology which can achieve rapid reconstruction of the die surface and suits for processing different types of cross section profiles.Because the three dimensional multi-point flexible stretch-bending of aluminum profile is a complex mechanical process,the quality of its forming parts is difficult to be accurately controlled,and the defects such as cross-sectional distortion,wrinkling and fracture are easily encountered.In order to improve the quality of the forming parts,reasonable control and optimization of the process parameters in the forming process are required.By systematically studying the three dimensional multi-point flexible stretch-bending forming,the prediction method and optimization plan of cross-sectional distortion were proposed.The main contents and results of this research are as follows:1.Use finite element simulation as the main research method to establish a finite element model of three dimensional multi-point flexible stretch-bending forming.The main contents of the research included the basic theory of finite element,the constitutive equation of material,the selection of element type,the reasonable simplification of models,the division of mesh,the contact and friction,and the setting up of boundary conditions.This section provided a theoretical basis for the following finite element simulation of three dimensional multi-point flexible stretch-bending forming process of aluminum alloy profile.2.Study the influence of process parameters on the cross-sectional distortion of the forming parts by using the method of controlling variable:(1)The cross-sectional distortion decreases with the increases of the number of multi-point die heads.When the number of multi-point die heads increases from 6 to 12,thecollapse rate decreases from 0.1231 to 0.0840,the bulging rate decreases from 0.0193 to0.0112.Therefore,the overall cross-sectional distortion becomes smaller.(2)The cross-sectional distortion increases with the increase of pre-stretching.When the pre-stretching amount increases from 0.8% L to 1.4% L,the collapse rate increases from0.0935 to 0.0981,the bulging rate increases from 0.0153 to 0.0208.Therefore,overall cross-sectional distortion becomes larger.(3)The cross-sectional distortion increases gradually with the increase of the post-stretching.When the amount of post-stretching increases from 0.8% L to 1.4% L,the collapse rate increases from 0.0943 to 0.0969,the bulging rate increases from 0.0164 to0.0170.Therefore,the cross-sectional distortion also becomes larger.(4)The cross-sectional distortion increases with the increases of friction coefficient.When the friction coefficient increases from 0.05 to 0.20,the collapse rate increases from0.0908 to 0.0969,and the bulging rate increases from 0.0141 to 0.0218.Therefore,the overall cross-sectional distortion becomes larger.(5)The collapse of profile is found to be the main deformation mode of cross-sectional distortion.3.Research on the process parameters of three-dimensional multi-point flexible stretch-bending forming:(1)Four factors and four levels of orthogonal test were established based on the pre-stretching amount,the post-stretching amount,the number of multi-point die heads,and the friction coefficient.Each parametric combination listed in the orthogonal table was numerically simulated using ABAQUS software,and the statistics of the test results were analyzed using the range difference method.On the collapse,the impact of the number of multi-point die heads is the most important,and that of the post-stretching is the least.On the bulging,the effect of friction coefficient is the most significant,and that of the post-stretching is the smallest.As a result,the optimum parameters was made as follows: the pre-stretching is 1.0% L,the post-stretching is 0.8% L,the number of multi-point die heads is 12,and the friction coefficient is 0.15.(2)The optimum parametric combination was verified by multi-point forming experiment.It was found that the finite element simulation can effectively predict the quality of the forming parts during the three dimensional multi-point stretch-bending,which can reduce the number of experiments,save the experimental cost,and shorten the experimental time.