Investigation On Process Parameters For Flexible-bending Process Of Tubes And Profiles

In order to achieve the requirements of light weight and toughness,bending of tubes and profiles has been used in petrochemical,urban and residential construction,vehicle,and aerospace industries so widely.As the bending tube aspect,the tube material not only have common stainless steel,copper alloy,as well as aluminum,magnesium,titanium,other alloys which are difficult to process forming materials.As the bending profile aspect,raw materials of profile have various shapes of cross-sections,including asymmetric cross-sections which are complex materials.Due to the difficult processing and forming of the tube material and the complex structure of the bending profile,its application is greatly limited in production.Therefore,we need to continuously improve the bending process and explore the most suitable production process to provide theoretical basis and data support for actual production.In this paper,the flexible-bending forming process is applied for forming of tubes and profiles.The new flexible-bending technique is used in 3-dimension(3D)bending of tube and profile cross-sections.The flexible,high-efficiency and digital forming of tubes and profiles can be easy to implement.The main research contents and conclusions of this paper are as follows:(1)Establishment of flexible bending forming modelBased on the principle of flexible-bending,the theoretical analysis of the bending of tube and profile,and the establishment of the geometric model of flexible-bending are carried out.The issues of meshing,material parameters,contact and friction,and boundary conditions involved are analyzed and resolved during establishing the model.(2)Comparative analysis of experiment and simulationFlexible-bending forming process was adopted to conduct the experiment and numerical simulation.Tubes and profiles were studied by experiments and numerical simulations.And they were compared and analyzed.The results show that under the condition of same offset,the bending curvatures of experimental and simulated parts are consistent.It proves the feasibility of flexible-bending numerical simulation.(3)Numerical simulation of flexible-bending of tubeTaking 304 stainless steel tube as experimental subject,the effect of offset on the thrust of the push block,the effect of wall thickness on thrust of the push block,residual stress,and springback were studied.The results show that with the increase of the offset of the bending die,the pushing force of the pushing block gradually increases;with the decrease of the wall thickness of the tube,the pushing force of the pushing block gradually decreases,the residual stress decreases in the inner and outer circumferences,the springback phenomenon increases;with the increase of outer diameter,the springback phenomenon is more and more obvious;forming speed has little effect on springback;with the change of wall thickness,both the wall thickness thickening rate and the thinning rate basically remain stable.(4)Research on the shape of bending dieTaking 304 stainless steel tube as experimental subject,the force of bending die and the residual stress were analyzed under the condition of two kinds of bending die.The results show that the axial non-eccentric bending die is feasible.(5)Numerical simulation on flexible-bending of profileTaking L-shaped aluminum as experimental subject,the effects of bending die parameters on side bends,twist defects,bending die forces and springback were analyzed during the forming process,and also wall thickness changes was studied.The results show that increasing the reverse displacement amount of the lateral bending can suppress the side bending defect;it can relieve distortion defect by increasing the reverse displacement of the lateral bending and changing the rotationaldegree of freedom along the coordinate axis;with the increase of the offset of the bending die in the Y direction,the springback can beoptimized according to the changing trend.