Research On Stretch Bending Forming Process For Large Curvature Profile By Numerical Simulation

Due to the increasing pressure from city transportation at present, people beginto choose subway and rail for travel. At the same time the Harbin-Dalian high-speedrailway and Beijing-Guangzhou high-speed railway are finished, attracting morepassengers to select the rail transportation with its advantages of convenient,comfortable, fast speed, large transport capacity, high security, low price. Stretch bendforming parts with its advantages of light weight and high strength, become one of theessential parts of the railway vehicle body structure. The stretch bend formingtechnology is crucial in railway manufacturing. The defect of wrinkling, springbackand cross-section distortion in the stretch bend forming influence the forming qualityseriously, so that the stretch bend forming technique has become the bottleneck ofhigh quality rail body manufacturing technology.The finite element simulation technology is one of the most important methodsof profile stretch bend forming research. Based on the simulation software ofABAQUS, the article does a research on L-section profiles and analyze the influencefactors of different materials, thickness, bending radius, mold space and stretching onthe wrinkling and springback. Concrete research contents as follows:1) Establishes the finite element model. In the model, only profile occursdeformation and the tool, jaw, baffle do not occur deformation, so the profile usesdeformable solid shell element and the tool, jaw, baffle use discrete rigid shell element.Because the symmetry of the model structure, load and constraint condition, can onlyestablish a half model, in order to reduce the computation time. The material of theprofile is the series of SUS301L stainless steel; Set the boundary conditions according to the calculated loading trajectory; Reasonably divides of the grid by considering thefactors of calculation accuracy and computation time; Established the finite elementmodel and then do the analysis of stretch bend forming process.2) There is wrinkling easily occurred in stretch bend forming and the severecase can affect the quality and disable to assemble. By compared the factors ofdifferent materials, thickness, bending radius, side plate space and stretch bendingparameter can draw the conclusion after simulation as flow: the higher of the materialyield strength, the larger of the thickness, the greater of the bending radius, the greaterof the stretching in the coating stage, the harder to occur wrinkling; The pre-andpost-stretching has a little impact on wrinkling; Reducing the mold space can help toreduce wrinkling.3) The springback is inevitable in stretch bend forming. The oversize springbackwill lead bad contour accuracy and affect assembly. Analyzes the factor of materials,thickness, bending radius and stretch bending parameters in order to reducespringback, then draws the conclusion as follow: the smaller of the material yieldstrength, the larger of the thickness, the smaller of bending radius and the greater ofthe stretching in coating stage, the smaller of the springback; The pre-andpost-stretching has a little impact on the springback.4) Takes a subway roof beam part as an example, its stretch bend forming processis optimized by simulation and the suitable process parameters are gotten.compensates the size of cross-section by the simulated result of the shrinkage andeliminate the cross-section distortion of undersize cross-section. Does the stretchbending experiment by the optimized process parameters. Eliminates thewrinkling,decreases the springback, improves the contour accuracy, obtains the highquality test piece and also proves the reliability of numerical simulation.