Bending Springback Prediction Method of Pipe Considering Elastic Modulus and Section Ellipse Distortion

Abstract

The invention discloses a pipe material bending springback prediction method capable of considering elastic moding and section elliptical distortion. The method comprises the following steps that: determining the plasticity coefficient, the hardening exponent and the wall thickness of a pipe material; on the basis of given pipe material characteristics, determining an initial elasticity modulus and an extreme value of the elasticity modulus along with plastic deformation, and solving an elasticity modulus nominal value which changes along with the plastic deformation in a pipe material bendingplastic deformation process; carrying out discretization processing on a pipe material bending part, and carrying out calculation to obtain an elliptical cross section bending moment; and solving a springback angle obtained after considering cross section elliptical distortion and elasticity modulus change in the pipe material bending part. By use of the method, the cross section elliptical distortion and the elasticity modulus change caused by plastic deformation in the pipe material bending process are introduced into pipe material bending springback calculation for the high-accuracy prediction of the pipe material bending springback angle.

Description

technical field [0001] The invention relates to a method for predicting bending springback of pipes, in particular to a method for predicting bending springback of pipes considering elastic modulus and section ellipse distortion. Background technique [0002] Plastic bending of pipes refers to the plastic deformation of pipes under the synergy of multiple moulds. Because it is easy to meet the requirements of light weight, precision and low consumption of products, this technology has been widely used in many fields such as aviation, aerospace, shipbuilding, chemical industry and automobile. At present, there are many kinds of pipe bending forming methods, among which the numerical control bending forming has the characteristics of high forming precision and high efficiency. [0003] During the bending and forming process of the pipe, a certain degree of springback will inevitably occur after bending unloading. When the springback exceeds the allowable range of the error, t...

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Problems solved by technology

[0004] At present, most of the theoretical analysis models of pipe bending springback are based on the classical springback theory (that is, the springback moment after bending unloading is equal to the loading moment during bending, and the direction is opposite), based on a large number of assumptions, such as Simplify the material as an ideal plastic material, ignoring the change of elastic modulus and wall thickness during the bending process of the pipe, as well as the distortion of the bending section of the pipe during the actual production process and the change of the elastic modulus during the plastic deformation of the pipe, etc. This will bring a large error to the rebound angle prediction

[0005] At the end of the plastic bending of the pipe, most of the cross-section of the bent part of the pipe has undergone irreversible plastic deformation, and the cross-sectional shape, size and elastic modulus of this part have changed. Therefore, according to the original cross-sectional shape and elastic modulus of the pipe There is a large error in the calculated springback angle. The existing technology does not consider the bending cross-section distortion and the change of the elastic modulus during the bending process of the pipe, and the error is large.

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