The Technological Theory And Numerical Simulation Analysis On The Multi Cross Rollers Straightening Process Of The Bimetals Composite Tube

Along with the swift development of the modern scientific technology, petroleum, chemical, geological exploration and other extreme conditions are demanding more and more requirements to metal tube. Not only high strength is required, but also it must has better high-temperature performance and exhibits good corrosion resistance. Duplex stainless steels and plenty of alloys can only partially meet the above conditions, while they contain rare metals, which is too expensive. Bimetals composite pipe is precisely meet these requirements and widely applied. At present, the main method of producing bimetals composite pipes are mechanical rolling method, explosive bonding, drawing composite method and hydraulic combined method. Each of these technologies has it’s own limitations, of which the main defects are on the curvature and ovality, which need straightening to eliminate, otherwise the products cannot be applicable to the variably situations. At present, our country has made a lot of progress in the theory research and industrial application of the steel tube multi-inclined roller straightening process. However, bimetal layered composite pipe has two kinds of mechanical properties of different material in the direction of the thickness of the wall, which of different elastic-plastic bending deformation behavior compared to single metal pipes. Whether the traditional straightening straight theory is still applicable to bimetal composite pipe, and composite pipe element contact interface in repeated bending process has damage risk of tear or not, all of these need further study. Therefore, this paper selects the multi rollers straightening process of the bimetals composite tube as the target, promoting the study of the composite pipe process theory and numerical simulation.In order to analysis bending deformation of composite tube wall thickness direction stress and strain distribution rules, chose the elastic element difference of Q235/TC4 composite pipe as the object, using finite element analysis software MSC. Marc, selecting a single straightening straight unit elastic plastic bending analysis, the inner and outer composite layer and the thickness ratio of the tube wall thickness direction stress and strain distribution are given. And on this basis, by simplifying conditions, calculation model of bending model of neutral layer and offset tube are analyzed. Based on the traditional straightening theory, combined with the composite pipe straightening condition, a suitable composite pipe inclined roll straightening theory is determined, which including roller straightening roll shape design, formulation of intermesh, crush and inclination angle of process parameters and by weighted calculation obtained composite pipe yield strength value, using this component yield strength of weighted value as composite pipe yield strength, computing the composite pipe straightening forces and straightening moments.Using nonlinear finite element method, the double layered metal composite pipe and inclined roller straightening model is established, and are constructed with initial ovality and bending of defects of composite tube geometry model, simulate specifications for composite pipe with diameter of 75 x 10 x 1000mm(Q235+TC4, layer thickness ratio was 4:1 and 1:4) cold straightening process, analyzes the straightening effect of ellipticity and bending degree of defects, the straightening process contains the stress and the strain of the rules, and straightening force distribution. By extracting the shear deformation of the composite interface and combining with the interfacial bonding strength of the existing composite technology, the possibility of re cracking of the composite interface in the process of straightening and bending was evaluated. Numerical simulation confirm that: single-layered tube bending theory cannot be applied to two-layered tube; the deviation of the neutral layer has been occurred to the tube bending; the defects of out-layer pipe who has high strength was eliminated, while inner-layer pipe who has low strength not. The existing simulation results are shown that straightening is not enough to tear the interface.