ExExperimental and numerical studies on the prediction of bendability limit of QSTE340 welded tube in NC bending process  

作　　者：YANG He REN Ning ZHAN Mei ZHANG ZhiYong QIN YaTao JIANG HaoMin DIAO KeShan CHEN XinPing 

机构地区：[1]State Key Laboratory of Solidification Processing,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi'an 710072,China [2]Baosteel Group Corporation,Shanghai 200122,China

出　　处：《Science China(Technological Sciences)》2012年第8期2264-2277,共14页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 50875216);111 Project (Grant No. B08040)

摘　　要：For a low carbon steel tube with small wall factor D/t and bending radius R,the over-thinning induced localized necking is one dominant failure in tube numerical control(NC) bending process,which strongly restricts the bendability limit of the tube.In addition,the deterioration of bendability of a tube is increased by the existence of the weak weld region.Therefore,an important issue is how to determinate and predict the welded tube bendability limit.In the present study,a finite element(FE) model with weld and subdivided heat affected zones under ABAQUS platform is employed to explore the deformation behaviors of welded tube NC bending.A localized necking criterion based on the critical thickness thinning is used to predict the critical principal strains,critical bending radius and burst location during the forming process.It is found that the failures always occur at the rigid supporting point of mandrel flexible balls near the tangent point at the outside of the bend,where the wall thickness of the tube is the lowest.The bending limit curves(BLCs) of the QSTE340 welded tube are obtained by shifting the standard shaped forming limit curve to the critical principal strains along the major strain axis.Comparison between the numerical and experimental results has shown that the BLC and critical bending radius predictions agree well with the experimental results.In addition,the effect of weld positions on BLC is discussed,the weld region shows an almost negligible effect on the forming limit at a non-critical location that is far away from the outside of the bend.However,when the weld is at the large tensile deformation region on the outside of the bend,a decrease of the forming limit strains is seen.

关 键 词：bendability limit welded tube NC bending FE simulation critical thickness thinning 

分 类 号：TG301[金属学及工艺—金属压力加工] V214[航空宇航科学与技术—航空宇航推进理论与工程]