Research On Deformation Behavior And Wrinkling Limit Of High Strength Steel Thin-walled Rectangular Tubes In The Induction Heating Bending Forming

The high strength steel(HSS)thin-walled tube-shaped components have been used in some automobile body structures at present,such as seat crossbeams,side-door impact beams,anti-collision beams,etc.,and their usage and application range have a tendency to expand rapidly with the continuous improvement of the dual requirements of lightweight and security in modern automobiles.The research and development of the forming theory and technology in the induction heating bending forming(IHBF)of HSS thin-walled tube is not only the urgent demand for the development of automotive technology,but also the important topic in the field of advanced plastic forming.However,the IHBF is a complex multi-nonlinear physical process with multi-dies synergy.It is urgent to solve the problem of wrinkling instability,especially prominent for bending thin-walled rectangular tube with small bending radius.Therefore,it is of great theoretical significance and practical value to systematically study the bending deformation behavior and wrinkling limit of HSS thin-walled rectangular tubes by using a combination of theoretical analysis,numerical simulation and experimental research.The high-temperature compression mechanical property test is carried out by using Gleeble-1500 D thermal simulation machine,and the high-temperature deformation behavior of B1500 HS high strength steel(HSS)is studied.The Arrhenius constitutive model of B1500 HS HSS considering strain compensation is established.Combined with the dynamic material model,the hot working maps of B1500 HS HSS are established using Murty instability criterion;at the same time,the prediction model for the critical strain model of dynamic recrystallization of B1500 HS HSS is established.The reasonable range of the strain rate and the deformation temperature in the IHBF and the ratio between critical strain and peak strain are determined.The numerical simulation models for the IHBF process of HSS thin-walled steel rectangular tube are established by analyzing the IHBF process of HSS thin-walled rectangular tube.The influence of the structure and width of the inductor and the power frequency on the the temperature field of rectangular tube is studied,which provides theoretical guidance for the selection of the process parameters and the design and manufacturing of equipment of the IHBF of the rectangular tube.The wrinkling regions can be predicted by using the numerical simulation model,and the mechanism,pattern and law of wrinkling instability in the IHBF of thin-walled rectangular tube are revealed,which provide a theoretical basis for establishing a quantitative wrinkling prediction model.According to the geometric characteristics of the wrinkling instability waveform of the thin-walled rectangular tube in the IHBF,a mathematic description of the wrinkling instability waveform on inner flange of thin-walled rectangular tube is proposed.Based on the energy method,and combined with the theory of thin-walled shell bending and the Hertz contact theory,considering the deformation temperature,the strain rate and the friction between the mandrel and rectangular tube,a quantitative prediction model of wrinkling limit of the IHBF process for thin-walled rectangular tube is established.Using the established prediction model for the wrinkling limit,the influence laws of geometric parameters and the deformation temperature of the rectangular tube on the wrinkling limit are obtained,and the accuracy of the prediction model for the process is verified by experiments.The experimental platform for the IHBF of rectangular tubes is constructed.Through bending forming experimental research,the influences of the distance between the mandrel core and the inductor,the number of mandrel cores,the distance between the push-bending roller and the inductor and the boost speed on the IHBF limit is revealed.The IHBF limit of B1500 HS HSS rectangular tube considering wall thinning,cross-section deformation and crack is acquired.Combined with FE numerical simulation and theoretical analysis,the key process parameters of the IHBF of B1500 HS HSS rectangular tube are determined.