This work develops a two-scales macro-micro approach to address the challenge in calibrating crystal plasticity microstructural models when samples undergo necking prior to fracture. The crystal plasticity models are crucial for predicting the materials’ plastic deformation and failure at the microstructure level, identifying the materials’ intrinsic properties as well as investigating the microstructure-properties relationships. However, after necking occurs, the experimentally measured stress-strain curves fail to reflect the materials ‘true’ stress-strain behavior and cannot be directly fitted into crystal plasticity models. The proposed macro-micro approach employs a top-down strategy to address this challenge, which has been studied with experimental tests on precipitation-strengthened Ni-based superalloy Haynes® 282®. In this approach, a macro rate-dependent anisotropic plasticity model with Voce-type hardening and Rice-Tracey damage law is first utilized to model the deformation and failure of the tensile bar, and calibrated by matching the stress-strain curves, necking strain, and reduction of area. Especially, to match the testing results under different applied strain rates, the rate-sensitivity parameter and saturation stress in the elasticity model are modified to incorporate dependence on the local strain rate. Then, the ‘true’ stress-strain behaviors are extracted from the necking zone of the macro-model, which are used to calibrate a micro-model with explicit microstructures and governed by an extended crystal plasticity law. The consistency between the micro-model and macro-model are enforced during calibration. The calibration outcomes from the crystal plasticity model elucidate the materials intrinsic properties for slip, hardening, and failure, which is vital for further investigations into the microstructure-properties relationship and for accurate prediction of the material behavior under various test and service conditions.

中文翻译：

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用于识别镍基合金海恩斯 282 颈缩和失效晶体塑性参数的宏观微观方法


这项工作开发了一种两种尺度的宏观-微观方法，以解决样品在断裂前发生颈缩时校准晶体塑性微观结构模型的挑战。晶体塑性模型对于在微观结构水平上预测材料的塑性变形和失效、识别材料的固有性能以及研究微观结构与性能之间的关系至关重要。然而，颈缩发生后，实验测量的应力-应变曲线无法反映材料“真实”的应力-应变行为，无法直接拟合到晶体塑性模型中。所提出的宏观-微观方法采用自上而下的策略来应对这一挑战，并通过对沉淀强化镍基高温合金 Haynes® 282® 的实验测试对其进行了研究。在这种方法中，首先利用具有 Voce 型硬化和 Rice-Tracey 损伤定律的宏观速率相关各向异性塑性模型来模拟拉伸杆的变形和失效，并通过匹配应力应变曲线、颈缩应变、以及面积的减少。特别是，为了匹配不同施加应变率下的测试结果，弹性模型中的速率敏感性参数和饱和应力被修改以纳入对局部应变率的依赖性。然后，从宏观模型的颈缩区域提取“真实”应力应变行为，用于校准具有明确微观结构并受扩展晶体塑性定律控制的微观模型。在校准过程中强制执行微观模型和宏观模型之间的一致性。 晶体塑性模型的校准结果阐明了材料滑移、硬化和失效的内在特性，这对于进一步研究微观结构-性能关系以及准确预测各种测试和使用条件下的材料行为至关重要。