Study On Intelligent Control Of Precise Stretch Bending Forming

Nowadays, stretch bending is an important method of bending of extrusions and has been used widely in aviation, spaceflight, weapon and automobile industry. Springback is a common phenomenon in stretch bending forming, is considered one of the problems and is caused by the elastic redistribution of the internal stresses during unloading. It greatly affects the precision of stretch bending part. Because of the complicated stress and strain state, it is difficulty to predict not only the amount of springback but also the variation of springback with the mechanical properties of the material and friction condition. Traditionally, experimental trial-and-error is required to select the process variables, and profile geometry and tooling. Sometimes the method of stretch bending, anneal and re-stretch bending must be applied, therefore the precision of shape can't be achieved by single stretch bending forming. These result in the high cost, low efficiency and can't satisfy the need of rapid manufacture. The literature on stretch bending forming with non-lateral compression can be fund. But, there is little literature on stretch bending forming with lateral compression and no literature on intelligent control of stretch bending forming can be fund so far.It can suit the variation of the mechanical properties of the material and improve the forming quality to use artificial intelligent control in stretch bending forming. The author has researched the deformation mechanism and the influences of process parameters, the mechanical properties of the material and friction condition on springback for stretch bending forming by theory analyzing and experimentation. Basing on these researches, the author developed an intelligent control model and system for stretch bending process with BP neural network, and realized intelligentcontrol in stretch bending process. The main content and conclusions are as follows.1. Using the assumption of uniaxial stress state and force equilibrium equation on the cross-section of the extrusion, the influences of the process parameters on spring-back have been obtained by mathematical analyzing for stretch bending with non-lateral compression.2. The formulation that calculates front axial force, back axial force and the friction coefficient between workpeces and mould is deduced. And from which the method is derived to measure the friction coefficient of stretch bending.3. The mathematical model of stretch bending with lateral compression is deduced...