一种改进的Lemaitre韧性断裂准则及其在旋压成形中的应用  

A Modified Lemaitre Ductile Fracture Criterion and Its Application to Spinning Forming

作　　者：吴卷[1] 詹梅[1] 蒋华兵[1] 陈飞[1] 杨合[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《航空学报》2011年第7期1309-1317,共9页Acta Aeronautica et Astronautica Sinica

基　　金：国家"863"计划(2008AA04Z122)~~

摘　　要：采用Lemaitre韧性断裂准则与有限元模拟相结合来预测材料在塑性成形过程中的开裂是广泛应用的一种方法,其中的Lemaitre准则是以损伤值与塑性应变呈线性关系为基础的,而实际一些材料的损伤值与塑性应变间却是非线性的。为此,本文将原Lemaitre准则中反映损伤值与塑性应变间的线性关系修正为非线性关系,得到了改进的Le-maitre准则。对比采用改进前后的Lemaitre准则对锥形件旋压和分形旋压开裂的预测结果表明,改进后的Lemaitre准则的预测结果更符合实际。采用改进后的Lemaitre准则在旋压成形中进行应用,获得了偏离率和芯模转速对锥形件旋压过程中损伤值分布和变化的影响。结果表明:零偏离时的损伤值较小,分布也较均匀;大的负、正偏离率下工件的损伤发生的区域不同,在大的负偏离率下,损伤主要发生在工件的顶部大拉应力作用区和旋轮作用下的变形区,在大的正偏离率下,旋轮和起皱后凸缘的干涉作用导致损伤主要分布在凸缘处;当进给比一定时,芯模转速越小,损伤发展越缓慢,越有利于工件的成形。Combining the Lemaitre ductile fracture criterion with finite element simulation is a method widely used in predic- ting the cracking of a workpiece in plastic forming. In the Lemaitre criterion, the relationship between the damage value and plastic strain is supposed to be linear, which is not the case for some materials that exhibit a nonlinear relationship. In this study, the Lemaitre criterion is modified by substituting linearity for non-linearity between the damage value and plastic strain of a workpiece. The comparisons on the prediction of cone spinning cracks and splitting spinning cracks using the original and modified Lemaitre criteria show that, the prediction of the modified Lemaitre criterion is in better agreement with experiment results. The influences of deviation and mandrel rotation on the distribution and variation of damage value during cone spin- ning are obtained by the modified Lemaitre criterion. The results show that, the damage value is the smallest and it is most evenly distributed at zero deviation, and the damage occurrence zone under a large negative deviation is different from that under a large positive deviation. For the former, damage mainly occurs in the top zone where large tension stress exists and where there is a contact deformation zone under the action of the rollers, but for the latter damage mainly occurs in the wrin- kled flange impacted by rollers. At a given feed ratio, the less the mandrel rotational speed, the slower the damage devel- ops, and the more helpful it is for cone spinning to continue successfully.

关 键 词：韧性断裂 Lemaitre准则 非线性 锥形件旋压 分形旋压 损伤 

分 类 号：V261[航空宇航科学与技术—航空宇航制造工程] TG302[金属学及工艺—金属压力加工]