A crystal plasticity finite element model embedding strain-rate sensitivities inherent to deformation mechanisms: Application to alloy AZ31
A crystal plasticity finite element model embedding strain-rate sensitivities inherent to deformation mechanisms: Application to alloy AZ31
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DOI：
10.1016/j.ijplas.2021.103031
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发表时间：
2021-05-26
影响因子：
9.8
通讯作者：
Knezevic, Marko
中科院分区：
文献类型：
--
作者：
Feather, William G.;Savage, Daniel J.;Knezevic, Marko
代表晶体粘塑性流动法则的基本幂律关系确保了在选择滑移系时的唯一性，该滑移系可容纳施加的塑性应变率。幂律关系也引入了一个人为的高应变率敏感性在晶体塑性模拟，除非使用高值的幂律指数。然而，指数的高值的使用受到数值易处理性的限制。提出了一种在晶体塑性有限元模型中嵌入反映材料应变率敏感性的幂律指数的数值方法。重要的是，该方法不会增加模拟中涉及的计算时间。利用改进的CPFE模型解释和预测了AZ 31镁合金复杂的应变率敏感响应和组织演化。在模拟中使用的滑移和孪生模式的应变率敏感性的测量值。计算结果表明，该模型成功地捕捉到了应变率变化对力学响应的影响，包括在10-3 s- 1 ~ 103 s-1的应变率范围内以及拉伸和压缩加载方向上的流变应力、织构和孪晶的演化。结果表明，这样的预测是一个后果，不仅相对量的滑移和孪生活动驱动的一组准确表征的硬化规律参数，但也值的应变率敏感性固有的个人变形机制。此外，该模型验证了测量的应变率依赖性的变形机制，同时准确地再现力学数据。因此，该模型可用于验证和进一步完善或推断测量的应变率敏感性，通过再现实验数据的变形机制。
The fundamental power-law relationship representing the flow rule in crystal visco-plasticity ensures uniqueness in the selection of slip systems accommodating imposed plastic strain-rates. The power-law relationship also introduces an artificially high strain-rate sensitivity in crystal plasticity simulations, unless a high value of the power-law exponent is used. However, the use of high values for the exponent is limited by numerical tractability. This paper presents a numerical method implemented in a crystal plasticity finite element (CPFE) model for embedding any value of the power-law exponent reflecting the true material strain-rate sensitivity. Importantly, the method does not increase computation time involved in the simulations. The enhanced CPFE model is used to interpret and predict a complex strain-rate sensitive response and microstructural evolution of AZ31 Mg alloy. Measured values of strain-rate sensitivity for slip and twinning modes are used in the simulations. Calculations show that the model successfully captures the phenomena pertaining to the effect of changing applied strain-rate on the mechanical response including flow stress and evolution of texture and twinning for a broad range of strain-rates ranging from 10-3 s- 1 to 103 s-1 and loading orientations in tension and compression. It is shown that such predictions are a consequence of not only relative amounts of slip and twinning activities driven by a set of accurately characterized hardening law parameters but also values of the strain-rate sensitivities inherent to individual deformation mechanisms. Besides, the model validates the measured strain-rate dependency of deformation mechanisms while accurately reproducing the mechanical data. Hence, the model can be used to verify and further refine or infer measured strain-rate sensitivity per deformation mechanism by reproducing experimental data.