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Predicting deformation behavior of α-uranium during tension, compression, load reversal, rolling, and sheet forming using elasto-plastic, multi-level crystal plasticity coupled with finite elements
Journal of the Mechanics and Physics of Solids ( IF 5.3 ) Pub Date : 2020-03-03 , DOI: 10.1016/j.jmps.2020.103924
Timothy J. Barrett , Rodney J. McCabe , Donald W. Brown , Bjørn Clausen , Sven C. Vogel , Marko Knezevic

An elasto-plastic self-consistent (EPSC) polycrystal plasticity formulation is adapted to model deformation of wrought α-uranium (α-U) accommodated by a combination of elasticity, dislocation glide, and deformation twinning. The EPSC model incorporates a strain-path, strain rate, and temperature sensitive dislocation density-based hardening law for the evolution of resistance to slip, twinning, and de-twinning and a slip system-level kinematic back-stress law to influence the driving force for activation. The model is used to interpret the complex deformation behavior of α-U as a function of strain-path and temperature. Samples of α-U with different initial orientation distributions are experimentally evaluated in simple compression, tension, and load reversal at room temperature and in compression and rolling at 573 K under a quasi-static deformation rate. Evolution of texture and twinning is characterized using electron backscattered diffraction and in-situ and ex-situ neutron diffraction during deformation. It is observed that the behavior of the material is highly anisotropic owing to its low-symmetry orthorhombic crystal structure and different activation stresses for crystallographic deformation modes. The model is calibrated and validated under these deformation conditions and predicts the stress-strain responses, amount of twinning, texture evolution, and lattice strains with one set of parameters for the hardening and back-stress evolution laws. Subsequently, the developed model is used as a constitutive law in the implicit finite element (FE) framework to simulate drawing of a hemispherical part from a rolled sheet of α-U. Here, the FE-EPSC model is a two-level homogenization scheme with EPSC relating the grain-level to the polycrystalline aggregate-level response, while the FE framework scales the polycrystalline to the part-level response. The simulation results and insights from the calculations, such as location dependent texture evolution is in good agreement with experiments.



中文翻译:

使用弹塑性,多级晶体可塑性与有限元结合,预测拉伸,压缩,反向载荷,轧制和片材成形过程中α-铀的变形行为

弹塑性自洽(EPSC)多晶可塑性公式适用于对变形的α-铀(α- U)的变形进行建模,该变形通过弹性,位错滑移和变形孪生相结合来适应。EPSC模型结合了基于应变路径,应变速率和温度敏感位错密度的硬化定律,以发展抗滑移,孪生和解缠的能力,并结合了滑移系统级的运动背应力定律来影响行驶激活力。该模型用于解释α- U的复杂变形行为与应变路径和温度的关系。α样本具有不同初始取向分布的-U在室温下的简单压缩,拉伸和载荷逆转以及在准静态变形速率下在573 K的压缩和滚动下的实验评估。织构和孪生的演化通过变形过程中的电子反向散射衍射以及原位和异位中子衍射来表征。可以看出,由于其低对称的正交晶体结构和不同的结晶变形模式激活应力,该材料的行为具有高度的各向异性。在这些变形条件下对该模型进行校准和验证,并使用一组用于硬化和反应力演化定律的参数来预测应力应变响应,孪生量,织构演化和晶格应变。后来,α- U 在此,FE-EPSC模型是一种两级均质化方案,其中EPSC将晶粒级与多晶聚集体级响应联系起来,而FE框架将多晶比例缩放到部分级响应。仿真结果和计算得出的见解(例如与位置有关的纹理演变)与实验非常吻合。

更新日期:2020-03-03
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