| Tube part of airplane is variety and its shapes are complexity. The request of forming quality is very strict. There are many thin-wall and large diameter tube parts in civil airplane. However there are many defects such as springback, shrinking, break, flattening and so on in the NC bending process of thin-wall and large diameter tube parts.In this paper, the analytical method was used to analyze the NC bending of tube which is thin-wall and large diameter. The analytical model of springback was founded. And the rules of the effect of the process parameters on springback were studied. The result of analyzing indicated that the larger A is, the larger springback angle is; the less Young's modulus is, the larger springback angle is; the larger relative radius bending is, the larger springback angle is.Through experimentation, the relations between process parameters and springback were summed up. And experimentation data was contrasted with the result of the analytical method. The result indicated that the relation of bend angle and springback angle of experimentation matched the analyzing for 20AG and there was a stabile difference between experimentation and analyzing.In this paper, the process database of NC tube bending was designed by analyzing the influence of process parameters and dies on the forming of tube. The user could query manufacturing records and the information of dies and benders which convenienced the selection of process parameters. Based on this process database, the springback angle could be obtained by using CBR which makes the number of experiment reduce and elevations the efficiency of NC tube bending.The plastic deformation theory for NC tube bending was studied. And the springback analytical models for thin-wall and large diameter tube was founded. Process database were developed. All of these have the academic and practical significance for solving the bending of thin-wall and large diameter tube.
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