Theoretical Analytical Model For Hydroforming Based On Plane Strain Theory

Hydroforming,also known as hydraulic bulging,is a modern plastic processing technology that utilizes pressure to deform tubes into complex shapes.It has the advantages of high strength,light weight,low tooling costs,great processing accuracy,and less subsequent processing steps,which made it more and more popular in the manufacturing applications for car body.Based on the plane strain theory,this paper aims to analyze the stress and deformation of the tube blank during hydroforming,and to establish an analytical model for describing the tube blank forming results.The major contents of this research are as follows:?1?under the condition of no axial feed,the tube blank is formed by internal pressure.Establishing the analytical model to describe the forming results of the neutral layer,inner layer and outer layer based on mechanical equations such as plane strain theory and power function law of stress-strain,combined with the bending effect in the process of tube deformation;verifying the accuracy of the analytical model by comparing the results of the strain,stress,thinning rate obtained from the analytical model with the results of numerical simulation.?2?introducing the ratio of axial stress,hoop stressand axial forceon the basis of no axial feed and redefine the axial strain;deducing the deformation process of high-pressure forming in tube fitting under axial feed condition and establish corresponding analytical model to predict tube blank forming results under high-pressure;verifying the applicability of the analysis model on axial feed conditions by comparing the results obtained from the analytical model with the results of numerical simulation.?3?analyzing the friction coefficient?,internal pressure,and strain hardening index9)of the tube blank and the mold independently by using the analytical model and evaluate the effects on forming results;establishing explicit function expression of the internal pressureand the axial feedby using analytical model to determine the axial feed under different internal pressures and obtain optimized loading path,resulting in the finding of certain improvement of formability compared with the traditional linear loading path.