Materials World Network: Physically based approach for predicting and minimizing damage nucleation in metals

预测损伤成核和评估是否会导致破坏的能力是计算塑性的一个主要目标。然而，大多数损伤建模是基于预先存在缺陷的假设，迄今为止发展的方法预测损伤的增长而不是成核。虽然非均质变形被认为是损伤成核的前兆，但从一种变形到另一种变形的步骤尚不清楚。当然，如果不准确地模拟非均质变形，那么就不可能自信地预测损伤成核或损伤生长。提出的研究旨在首次从损伤成核点周围的晶粒系综中获得一组适当详细的数据，以确定多晶边界处相应的机制。通过电子通道对比成像、电子背散射衍射、聚焦离子束铣削和数字图像相关，原位测量了塑性变形过程中空间分辨滑移和孪晶系统活性、晶体取向、晶格旋转、三维晶界立体学和局部表面应变。这一广泛而独特的数据集有助于评估中尺度形变模式的改进。通过对各自晶粒系综的验证晶体塑性有限元模拟的补充结果来补充实验观察，有可能对操作损伤成核机制有新的见解。由此推导出适当的损伤成核模型，可以从捕获成核的代表性体积的晶粒尺度模拟过渡到损伤生长/传播的连续尺度模拟。

The ability to predict damage nucleation and evaluate whether it will lead to failure is one major goal of computational plasticity. However, most damage modeling is based upon the assumption of pre-existing flaws, and approaches developed so far predict growth rather than nucleation of damage. While heterogeneous deformation is understood to be a precursor to damage nucleation, the step from one to the other is not clearly understood. Certainly, if heterogeneous deformation is not modeled accurately, then it is unlikely that damage nucleation, or damage growth can be confidently predicted. The proposed research seeks to obtain for the first time a suitably detailed set of data from grain ensembles around damage nucleation sites to identify the corresponding mechanisms at polycrystal boundaries. Spatially resolved slip and twin system activity, crystal orientation, lattice rotations, 3D grain boundary stereology, and local surface strain during plastic deformation is measured in situ by electron channeling contrast imaging, electron backscatter diffraction, focused ion beam milling, and digital image correlation. This extensive and unique data set facilitates the evaluation of improvements in mesoscale deformation models. By complementing experimental observations with supplemental results from verified crystal plasticity finite element simulations of the respective grain ensembles new insights into the operating damage nucleation mechanism(s) are possible. Deriving appropriate damage nucleation models from this will allow to bridge from grain-scale simulations of representative volumes where nucleation is captured to continuum-scale simulations of damage growth/propagation.