Study On Bending Forming Of Tailor Rolled Blank Tube

TRB tube is made of tailor rolled blank(TRB)with continuous thickness change by bending,stamping,laser welding and other processes.TRB tube has unique hollow structure and wall thickness partition due to thickness difference.On the one hand,it can meet the purpose of lightweight,strengthening and toughening.On the other hand,it can achieve strength differentiation,that is,different strength requirements correspond to different thickness areas.In the process of tube bending,the stress distribution is not uniform,which leads to the reduction of outside thickness and the increase of inside thickness.In order to find out whether the TRB tube can adapt to the uneven stress distribution in the process of bending to obtain the bending parts with higher forming quality,the influence of thickness of thin zone,the length of transition zone and the thickness difference of transition zone on the bending quality of TRB tube is studied,and the three structural parameters are optimized;The influence of bending speed,clearance between mandrel and the tube wall and the width of mandrel ball head on the quality of TRB tube are studied;The decentration TRB tube is designed.The influence of bending angle and bending radius on forming quality is studied,and the prediction formula of wall thickness in the stable deformation zone is deduced.The no-mandrel bending finite element model of TRB tube was established.The effects of thickness,thickness difference and length of transition zone were studied.Increasing thickness of the thin zone,reducing length and thickness difference of the transition zone can improve the bending forming performance,but the effect on the thickening rate is not obvious.In order to improve the quality of bending forming,an approximate model between quality evaluation index and structural parameters was established and verified.Then,the structural parameters were optimized.The results show that the error between the optimization and simulation solution are less than 5%,indicating the reliability of the conclusion;Compared with the initial value,the thickness reduction rate decreased by 0.369%,the thickening rate decreased by 0.313%,the short-axis change rate decreased by 1.852%,and the bending forming performance was improved,which indicates that the optimization method has good practicability.The finite element models of ball and socket flexible mandrel and TRB tube with mandrel are established.The effects of bending speed,clearance between mandrel and tube wall,and the width of mandrel ball head on the maximum wall thickness reduction rate and the maximum wall thickness thickening rate of TRB tube are studied.The results show that the larger the gap between mandrel and the tube wall is,the larger the maximum thinning rate of wall thickness is,and the effect of bending speed and ball head width on the thinning rate is not obvious;Too large or too small the bending speed,the gap between mandrel and tube wall,and the ball head width are not conducive to the improvement of the forming quality of the inside tube wall.According to the law of tube bending,the tailor rolled blank tube with decentration structure(decentration TRB tube)is designed.The model of mandrel bending of decentration TRB tube is established,and the bending law of decentration TRB tube are explored.The influence of angle and radius on quality of decentration TRB tube are studied.The results show that the thickness reduction rate of decentration TRB is lower than equal thickness tube,which is suitable for the application scenarios where the forming accuracy is not high but the performance is high;The effect of angle on the forming quality of decentration TRB tube is not obvious.Increasing the bending radius is conducive to improving the forming quality of decentration TRB tube,but when the bending radius is too large,the effect of reducing wrinkle will become less obvious;the error of the tube’s outside thickness calculated by the prediction formula of the wall thickness of the stable deformation area is less than 5%.Considering the influence of wrinkle,the error of the tube’s inside thickness calculated by the formula after the adjustment is between 6% and 7%,which shows that the prediction method has certain reference significance.