Jeong Y, Iadicola M A, Gnäupel-Herold T, Creuziger A
Center for Automotive Lightweighting, National Institute of Standards and Technology, USA.
University of Maryland College Park, USA.
Acta Mater. 2016 Jun 15;112:84-93. doi: 10.1016/j.actamat.2016.04.013. Epub 2016 Apr 18.
Constitutive behaviors of an interstitial-free steel sample were measured using an augmented Marciniak experiment. In these tests, multiaxial strain field data of the flat specimens were measured by the digital image correlation technique. In addition, the flow stress was measured using an X-ray diffractometer. The flat specimens in three different geometries were tested in order to achieve 1) balanced biaxial strain, and plane strain tests with zero strain in either 2) rolling direction or 3) transverse direction. The multiaxial stress and strain data were processed to obtain plastic work contours with reference to a uniaxial tension test along the rolling direction. The experimental results show that the mechanical behavior of the subjected specimen deviates significantly from isotropic behavior predicted by the von Mises yield criterion. The initial yield loci measured by a Marciniak tester is in good agreement with what is predicted by Hill's yield criterion. However, as deformation increases beyond the vonMises strain of 0.05, the shape of the work contour significantly deviates from that of Hill's yield locus. A prediction made by a viscoplastic self-consistent model is in better agreement with the experimental observation than the Hill yield locus with the isotropic work-hardening rule. However, none of the studied models matched the initial or evolving anisotropic behaviors of the interstitial-free steel measured by the augmented Marciniak experiment.
采用改进的Marciniak试验测量了一种无间隙钢样品的本构行为。在这些试验中，通过数字图像相关技术测量了扁平试样的多轴应变场数据。此外，使用X射线衍射仪测量了流动应力。测试了三种不同几何形状的扁平试样，以实现：1）平衡双轴应变，以及在2）轧制方向或3）横向方向上零应变的平面应变试验。处理多轴应力和应变数据，以获得相对于沿轧制方向的单轴拉伸试验的塑性功等值线。实验结果表明，受试试样的力学行为明显偏离了von Mises屈服准则预测的各向同性行为。Marciniak试验机测量的初始屈服轨迹与Hill屈服准则的预测结果吻合良好。然而，当变形增加到超过0.05的von Mises应变时，功等值线的形状明显偏离Hill屈服轨迹。与具有各向同性加工硬化规则的Hill屈服轨迹相比，粘塑性自洽模型的预测与实验观察结果更吻合。然而，所研究的模型均未与改进的Marciniak试验测量的无间隙钢的初始或演变各向异性行为相匹配。
