Abstract This is the second part of a two-part contribution on modeling of the anisotropic elastic-plastic response of aluminum 7079 from an extruded tube. Part I focused on calibrating a suite of yield and hardening functions from tension test data; Part II concentrates on evaluating those calibrations. A rectangular validation specimen with a blind hole was designed to provide heterogeneous strain fields that exercise the material anisotropy, while at the same time avoiding strain concentrations near sample edges where Digital Image Correlation (DIC) measurements are difficult to make. Specimens were extracted from the tube in four different orientations and tested in tension with stereo-DIC measurements on both sides of the specimen. Corresponding FEA with calibrated isotropic (von Mises) and anisotropic (Yld2004-18p) yield functions were also conducted, and both global force-extension curves as well as full-field strains were compared between the experiments and simulations. Specifically, quantitative full-field strain error maps were computed using the DIC-leveling approach proposed by Lava et al. The specimens experienced small deviations from ideal boundary conditions in the experiments, which had a first-order effect on the results. Therefore, the actual experimental boundary conditions had to be applied to the FEA in order to make valid comparisons. The predicted global force-extension curves agreed well with the measurements overall, but were sensitive to the boundary conditions in the nonlinear regime and could not differentiate between the two yield functions. Interrogation of the strain fields both qualitatively and quantitatively showed that the Yld2004-18p model was clearly able to better describe the strain fields on the surface of the specimen compared to the von Mises model. These results justify the increased complexity of the calibration process required for the Yld2004-18p model in applications where capturing the strain field evolution accurately is important, but not if only the global force-extension response of the elastic-plastic region is of interest.

中文翻译：

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挤压铝 7079 的各向异性塑性模型形式：第 I 部分，校准

摘要 这是对挤压管的 7079 铝的各向异性弹塑性响应建模的两部分贡献的第二部分。第一部分侧重于根据拉伸测试数据校准一组屈服和硬化函数；第二部分专注于评估这些校准。带有盲孔的矩形验证样本旨在提供行使材料各向异性的异质应变场，同时避免难以进行数字图像相关 (DIC) 测量的样品边缘附近的应变集中。从管子中以四个不同的方向提取样品，并在样品两侧用立体 DIC 测量进行拉伸测试。还进行了带有校准的各向同性 (von Mises) 和各向异性 (Yld2004-18p) 屈服函数的相应 FEA，并在实验和模拟之间比较了全局力 - 延伸曲线以及全场应变。具体而言，使用 Lava 等人提出的 DIC-leveling 方法计算了定量全场应变误差图。试样在实验中与理想边界条件有很小的偏差，这对结果具有一阶影响。因此，必须将实际的实验边界条件应用于 FEA，以便进行有效的比较。预测的全局力扩展曲线与总体测量结果一致，但对非线性区域的边界条件敏感，无法区分两个屈服函数。对应变场的定性和定量研究表明，与 von Mises 模型相比，Yld2004-18p 模型显然能够更好地描述试样表面的应变场。这些结果证明了 Yld2004-18p 模型在准确捕获应变场演化很重要的应用中所需的校准过程的复杂性增加是合理的，但如果仅对弹塑性区域的全局力扩展响应感兴趣则不然。