Research On Stamping And Springback Behavior Of Saddle-shaped Curved Beam With Variable Radius

With convenience and efficiency,the rail transportation vehicle is constantly enriching the travel choices and improving lifestyles for people around the world,and the technical development of lightweight materials and lightweight structures play important parts in global environmental protection.The stamping process have widely applications,especially in rail vehicle yield,because of high forming accuracy and high material utilization in large-size frame-type thin sheet workpiece process.For SUS301LN-1/16 H,good mechanical properties could guarantee the strength and rigidity for body structure,high temperature resistance and corrosion resistance ensure the safe operation of rail transportation vehicles in different environments.The comprehensive performances make it to be the first choice for vehicle body materials.The variable radius saddle-shaped curved beam is the main component connecting the rail vehicle roof,vertical pillars and body skin.The longitudinal profile is an asymmetric structure formed by two arc-shaped segments with large radius differences,the transverse section is symmetric saddle-shaped.Because of multiple influencing factors,the complex three-dimensional structural parts could not be controlled effectively.There are deficiencies in original curved beam design.At first,when rectangle blank is used,punching depths differ at different cross sections,there are some differences in material flow speed and plastic compensation.On the one hand,the wing outer edge retracts and the straightness cannot meet the assembly requirement.On the other hand,lots of invalid forming area must be cut and wasted.Secondly,the whole springback is complex.The deflection of the longitudinal profile is manifested as both ends open and middle upward,the springback in the largecurvature left is larger than the small-curvature right.The vertical wall opening angle and wing warping happened in transverse section are completely different from the longitudinal one.All springback types lead to more serious dimensional accuracy deviation.In order to improve the processing accuracy and control the whole springback,in this paper,the variable radius saddle-shaped curved beam forming mold for a railway vehicle was designed in CATIA software,the forming simulation and springback analysis for the part were done in finite element software ABAQUS.Aiming at the straightness of the wing outer edge and the cutting waste of the invalid forming area,an unfolding blank optimization scheme with irregular shape was proposed to optimize stress distribution and material flow compensation,attain the straightness of 1000:1 and cancel cutting waste.Based on the simulation test of longitudinal radius combinations,five combinations were obtained as alternatives and reserve some over-formation or springback compensation in different directions.Through the single factor studies of saddle-shaped straight workpiece,the influences of fillet radius group,mold gap and friction coefficient were analyzed and ensured.The main contents are as follows:(1)Though the finite element simulation,the forming size defects of rectangular unfolding blank were characterized to analysis the relationship of material flow in different deformed areas,finally a size-compensated unfolding blank optimization scheme was determined.(2)For springback problems of longitudinal profile,the optimal design of transition radius combination was proposed,and reasonable parameter groups range was confirmed.For the wing springback of transverse section,the influences of fillet radius,mold gap and friction coefficient on springback were simulated.(3)The orthogonal experiment was designed to test and analyze the whole springback combined with longitudinal profile and transverse section,and the optimal parameter combination was determined of the longitudinal radius combination R328-R1248,the fillet radius group r5-r8,the mold gap 3.580 mm,and the friction coefficient 0.16.Based on the above research,the simulation calculation results were tested and verified.The results show that the whole springback of formed part is well controlled,the maximum springback range is 0.300~0.350 mm,and the dimensional accuracy of the variable radius saddle-shaped curved beam meets the process requirements.