Research On Bimetal Tube Forming By Hydroforming

Bimetal tube is a new type of composite tube which is tightly combined with two different materials by means of plastic deformation or connection technology.Compared to the traditional single metal tube, bimetal tube makes full use of the excellent properties of two kinds of metal tube, It has been applying widespreadly in many domains. Bimetal tube hydroforming has the merits of simple process, gradual compression molding, no scratch or damage on the inner surface of the tube, and it is a kind of green processing technology, which uses the material properties of the metal to realize the forming of liner tube and base tube. Based on theoretical analysis and numerical simulation, this dissertation studies the process of bimetal tube hydroforming.The main content of this dissertation includes the following sections:(1) Based on elastic-plastic theory,the stress and deformation for the liner tube and base tube are analyzed during the process of hydroforming,according to deformation compatibility condition derived the formula of contact pressure between layers and residual contact pressure related to hydro-expanded pressure and the variable range of hydro-expanded pressure. Bimetal tube hydroforming theory was verified by experiment and finite element simulation(using ABAQUS).(2) Used orthognal experiment design, select the ratio of outer and inner diameter of liner tube, the ratio of outer and inner diameter of base tube, the initial clearance of liner tube and base tube, tube length, pressuring time as the experimental factors, three levels for each experimental factor. The effects of hydroforming parameters on residual contact pressure and thickness distribution index were obtained according to the simulation result by the methods of range analysis and variance analysis.(3) Research on the effects of temperature loading on contact pressure between layers of bimetal tube,analyzed the critical yield temperature of bimetal tube under thermal loading and critical layer temperature under thermal unloading,mechanical analysis of bimetal tube, derived the variable range of bimetal tube working temperature and verified by finite element simulation.Analysis the influence of residual contact pressure,working pressure,line expansion coefficient and wall thickness to the working temperature range of bimetal tube.This dissertation studies the process of bimetal tube hydroforming,provides reliable theoretical gist and technical specification for the production of the bimetal tube hydroforming, the studies have important theoretical significance and practical guiding significance.