Research On The Stretch Bend Forming Of Railway Vehicle Stainless Steel Profile Components By Numerical Simulation And Experiment

In recent years, the rapid development of rail transportation promoted the profile components of a large number of applications. Railway vehicle body materials are aluminum alloy and stainless steel mostly. Because of its better mechanical properties, fire prevention performance, corrosion resistance and appearance, stainless steel car body become the mainstream direction in the development of contemporary and future rail transit system. Stretch bending is the main stainless steel car body profile component forming method. However, the process of stretch bending forming process is complex, and stainless steel profile deform difficultly, the current profile components are prone to some shortcomings, such as wrinkling, cross section distortion and poor contour accuracy, which seriously affects the product quality and yield. For half a century, the domestic and foreign scholars have put forward the analytic method, experimental method and numerical simulation method and other methods to study the stretch bending process. Using numerical simulation technology can have a comprehensive systematic research to process of stretch bending deformation and the springback after forming. What’s more, numerical simulation technology’s production efficiency is higher and its cost is lower. Simulation accuracy has been verified. Therefore, this paper used numerical simulation method for railway vehicles bodywork profile to study the component of the stretch bending forming. The main results have the following several aspects:1) Mechanics performance of series of SUS301L stainless steel on vehicle was systematically experimental studied, and accurate data of the mechanics properties was obtained, which lay a foundation for car body components’s forming simulation.2) A three-dimensional dynamic explicit finite element analysis model of profiles stretch bend forming’s simulation was established. A reasonable description method of stretch bend forming’s trajectory was put forward, and the calculation formula was presented. The complex boundary conditions, such as displacement and angle were accurately load.3) Wrinkle defect of the stretch bend forming and its main influencing factors was studied by simulation. The results show that profile with high strength and large thickness is not easy to wrinkle, and pre-elongation and post-elongation have few influence on wrinkling, meanwhile increasing the wrap-elongation can significantly reduce the wrinkling defect, so using reasonable process parameters is an effective measure to control wrinkle defect. The higher profile vertical edge, the component wrinkle more easily. The limit height of vertical edge with no wrinkle was determined by simulation, which provides reliable reference for the design of stretch bending parts. 4) The mechanism, main influencing factors and controlling method of cross section distortion of stretch bend forming were studied. The results show that increasing the elongation of stretch bend forming can deteriorate the cross section distortion defect. The process parameters should be chosen reasonably in practice. The shrinkage compensation to profile’s cross section can eliminate eversion distortion defects. The mold profile has an important influence on section’s deformation, and inaccurate mold profile can produce a variety of types of cross section distortion, which deteriorates the quality of the products. Reasonable process parameters, accurate compensation to profile section, and accurate design of mold profile can effectively reduce or even eliminate the cross section distortion defects.5) A three dimensional static implicit finite element model for springback simulating was established, and main influencing factors of springback were studied. The results show that the greater the strength of materials, the higher springback of the stretch bend forming. The smaller the thickness of profile, the bigger the springback. The springback increases with the increase of bending radius and the decrease of the bending angle. In stretch bending process parameters, increasing the pre-elongation and post-elongation can reduce springback, but the impact is small, while increasing the wrap-elongation can significantly reduce springback. Using the optimized process parameters and precisely compensated stretch bending mold can effectively control the bending precision of outline, and obtain forming parts with high quality.