Texture, hardening and non-proportionality of strain in BCC polycrystal deformation
Texture, hardening and non-proportionality of strain in BCC polycrystal deformation
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DOI：
10.1016/j.ijplas.2013.04.008
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发表时间：
2013-11
影响因子：
9.8
通讯作者：
T. Erinosho;A. Cocks;F. Dunne
中科院分区：
文献类型：
--
作者：
T. Erinosho;A. Cocks;F. Dunne
用晶体塑性有限元框架研究了单晶和多晶体心立方钢的应变、初始织构和硬化的非均衡性。对于体心立方多晶，还预测了硬化对可达到的延性的影响。研究了两种极端的硬化形式，即各向同性潜伏性硬化和各向异性自硬化。为了研究位错分布的建立及其对非比例性、硬化和初始织构的依赖关系，计算了所有独立滑移系上的位错密度演化。首先考虑体心立方单晶的结果，以便深入了解后续的多晶研究。应变过程中的非比例程度，同时在所有情况下保持相同的最终应变状态，已被证明导致适度不同的最终应力状态，非比例程度越高，与相应的比例应力状态的偏离越大。硬化的性质也影响了非比例效应的强度，各向同性潜伏硬化导致了比各向异性自硬化更大的应力非比例效应。已建立的多晶位错分布取决于非比例的程度，特别是在单轴应变条件下(与双轴应变相反)，并且非常强烈地取决于所假设的硬化的性质，但对初始织构的影响较小。此外，在非比例双轴应变路径下，预测的极限应变受到中等程度的影响，而在非比例单轴应变路径下，预测的极限应变增加更显著。已有研究表明，非比例性在应变局部化的建立过程中起着关键作用，从而决定了成形极限。
Non-proportionality of straining, initial texture and hardening has been investigated in single- and polycrystal BCC steel using a crystal plasticity finite element framework. The effect of hardening on achievable ductility is also predicted for a BCC polycrystal. Two extreme forms of hardening have been investigated; namely, isotropic latent hardening and anisotropic self-hardening. Dislocation density evolutions on all independent slip systems have been calculated in order to investigate the establishment of dislocation distributions and their dependence on non-proportionality, hardening and initial texture. Results for a BCC single crystal are considered first in order to provide insight into subsequent polycrystal investigations.The degree of non-proportionality during straining, whilst maintaining in all cases the identical, final strain state, has been shown to lead to moderately differing final stress states, with a higher degree of non-proportionality giving the largest divergence from the corresponding proportional stress states. The nature of the hardening is also found to influence the strength of the non-proportionality effect, with isotropic latent hardening leading to the development of greater non-proportionality effects on stress than those for anisotropic self-hardening in polycrystals. The polycrystal dislocation distributions established are found to depend on the degree of non-proportionality, particularly under uniaxial straining conditions (as opposed to biaxial straining), and very strongly on the nature of the hardening assumed, but less so on the initial texture. In addition, the predicted limit strain is moderately affected under non-proportional biaxial strain paths as opposed to more significant increases under non-proportional uniaxial strain paths. It has been shown that that non-proportionality plays a key role in the establishment of strain localization and hence on forming limits.