金属剪切旋压成形时的韧性断裂准则

Ductile Fracture Criterion for Metal Shear Spinning

破裂是剪切旋压时最主要的失效形式。为实现对剪切旋压时破裂的精确预测,根据剪切旋压成形时变形区材料的受力特点,提出对基于材料压缩变形塑性本构模型的Oyane准则进行研究。以DP600高强钢为研究对象,通过ABAQUS软件的VUSDFLD子程序二次开发,将Oyane准则耦合到剪切旋压有限元模型进行断裂损伤的计算及断裂阈值的判断。通过椭球形芯模旋压试验对断裂预测结果进行验证。结果表明,基于Oyane准则模拟得到的断裂危险位置位于已变形区靠近变形区处并沿着切向均匀分布,与试验结果的分布规律一致;但基于模拟所得到的极限减薄率与试验结果之间的相对误差达到33.8%。在Oyane准则的基础上,通过考虑平均应力和最大剪切应力对韧性损伤过程的影响,构建出适用于剪切旋压成形的修正韧性断裂准则。结果表明,采用修正后的韧性断裂准则,模拟得到的极限减薄率与试验结果的相对误差仅为15.9%;与Oyane韧性断裂准则相比,相对误差减小了17.9%。获得适用于剪切旋压时的韧性断裂准则,为金属剪切旋压成形破裂的精确预测奠定理论基础。

Fracture is the main failure mode during shear spinning. The investigation of Oyane criterion based on constitutive mode of compression plastic deformation is proposed according to the stress state of the deformation zone during shear spinning to realize the accurate prediction of fracture. The Oyane ductile criterion is coupled to the finite element model of shear spinning of DP600 high strength steel based on the secondary development through the subroutine VUSDFLD of software, ABAQUS. The damage integral calculation of Oyane ductile criterion and the judgment of fracture threshold during shear spinning are carried out. The spinning experiment with ellipsoid mandrel is carried out to verify the simulation results of fracture prediction. The results show that the fracture position during shear spinning predicted by Oyane criterion is located in the deformed zone near the deformation zone and distributed uniformly along the tangential direction, which is in good agreement with the experimental result. However, the relative error of the maximum thinning ratio between the simulation and experiment reaches to 33.8%. Therefore, a modified ductile fracture criterion based on the Oyane criterion for fracture prediction during shear spinning is proposed by considering the influence of mean stress and maximum shear stress on the ductile damage process. The results show that the relative error of maximum thinning ratio predicted by the modified criterion is only 15.9%, which is decreased by 17.9% compared with the Oyane ductile fracture criterion. The ductile fracture criterion applied to metal shear spinning is obtained, which can provide the theoretical basis for the accurate prediction of fracture during metal shear spinning.