Abstract

Effects of evolution in anisotropy during plastic deformation under strain path changes on the formability and failure were investigated in the present study. The evolution in anisotropic property of the extra deep drawing steel was considered by implementing the non-quadratic anisotropic yield function Yld2000-2d as a function of effective plastic strain, and the corresponding forming behaviour in two-step forming processes was analysed. For the strain path effect, pre-strain was applied under biaxial mode using Marciniak in-plane stretch forming set-up, followed by the secondary deformation using the out-of-plane stretch forming tool. For failure prediction of the proposed two-step forming, different failure limit approaches were investigated. First, a strain based forming limit diagram (FLD), proposed as the Marciniak–Kuczynski model was modified to include the evolution in anisotropic yield function. The dynamic shift in FLD was also determined by taking strain path change into consideration. In addition, the influence of evolution of yield function on the strain path independent failure limit criteria was also assessed in terms of stress based forming limit diagram. Finally, the prediction accuracy of the failure limit criteria was compared among different models in terms of failure location and limiting dome height (LDH). It was observed that the incorporation of evolution in anisotropic yield surface improved the prediction of formability in terms of the LDH and strain distribution for the investigated material.

Graphic Abstract

中文翻译：

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应变路径变化过程中各向异性的发展对钣金破坏极限的影响

摘要

在本研究中，研究了应变路径变化下塑性变形过程中各向异性的演变对可成形性和破坏的影响。通过实现非二次各向异性屈服函数Yld2000-2d作为有效塑性应变的函数，来考虑超深拉伸钢各向异性的演变，并分析了两步成形过程中相应的成形行为。对于应变路径效应，使用Marciniak平面内拉伸成形装置在双轴模式下施加预应变，然后使用平面外拉伸成形工具进行二次变形。对于所提出的两步成形的失效预测，研究了不同的失效极限方法。首先，基于应变的成形极限图（FLD），提出的Marciniak-Kuczynski模型经过修改以包括各向异性屈服函数的演化。还通过考虑应变路径的变化来确定FLD的动态位移。此外，还根据基于应力的成形极限图评估了屈服函数的演变对与应变路径无关的破坏极限标准的影响。最后，根据故障位置和极限球顶高度（LDH），比较了不同模型之间的故障极限准则的预测准确性。观察到，在各向异性屈服面中掺入了析出物，从而改善了所研究材料的LDH和应变分布方面的可成形性预测。还通过考虑应变路径的变化来确定FLD的动态位移。此外，还根据基于应力的成形极限图评估了屈服函数的演变对与应变路径无关的破坏极限标准的影响。最后，根据故障位置和极限球顶高度（LDH），比较了不同模型之间的故障极限准则的预测准确性。观察到，在各向异性屈服面中掺入了析出物，从而改善了所研究材料的LDH和应变分布方面的可成形性预测。还通过考虑应变路径的变化来确定FLD的动态位移。此外，还根据基于应力的成形极限图评估了屈服函数的演变对与应变路径无关的破坏极限标准的影响。最后，根据故障位置和极限球顶高度（LDH），比较了不同模型之间的故障极限准则的预测准确性。观察到，在各向异性屈服面中掺入了析出物，从而改善了所研究材料的LDH和应变分布方面的可成形性预测。根据故障位置和极限球顶高度（LDH）在不同模型之间比较了故障极限准则的预测准确性。观察到，在各向异性屈服面中掺入了析出物，从而改善了所研究材料的LDH和应变分布方面的可成形性预测。根据故障位置和极限球顶高度（LDH）在不同模型之间比较了故障极限准则的预测准确性。观察到，在各向异性屈服面中掺入了析出物，从而改善了所研究材料的LDH和应变分布方面的可成形性预测。

图形摘要