The formation of crevasses in Greenland and Antarctica is primarily driven by the brittle failure of ice at low strain rates. Understanding this phenomenon requires exploring the effect of microstructural heterogeneity and anisotropic elastoplastic deformation on the fracture behavior of ice. Here, we have developed a microstructure-sensitive coupled crystal plasticity and phase-field model. This model allows us to study the plastic deformation, damage initiation and propagation under various strain rates in hexagonal open-packed polycrystalline ice, the prevailing phase on Earth. By employing a Bayesian optimization method, we derived the material parameters for the micromechanical model based on experimental results. The modeling results reveal that the activation of basal dislocations results in a brittle to ductile transition in ice at a low strain rate of 10-7s-1 under tension. At higher strain rates, the intrinsic plastic anisotropy of ice leads to heterogeneous deformation among grains and stress concentration near grain boundaries, triggering crack initiation and exacerbating the brittleness of ice. Under compression, cracks usually do not propagate throughout the specimen due to a significant decrease in stress around the crack tip upon propagation. Moreover, we found that the formation of the shear-induced basal texture at the bottom of ice layers and along glacier valley sides intensifies the brittleness of ice. This study provides insights into the micromechanical deformation and fracture mechanisms of ice, elucidating the intricate process of crevasse development in polar ice sheets.

中文翻译：

---

多晶冰中微结构敏感的晶体塑性和变形和断裂的相场建模


格陵兰岛和南极洲裂缝的形成主要是由冰在低应变率下的脆性破坏驱动的。要了解这种现象，需要探索微观结构异质性和各向异性弹塑性变形对冰裂隙行为的影响。在这里，我们开发了一个对微观结构敏感的耦合晶体塑性和相场模型。该模型使我们能够研究六边形开堆积多晶冰（地球上的主要相）中各种应变速率下的塑性变形、损伤起始和传播。通过采用贝叶斯优化方法，我们根据实验结果推导出了微观力学模型的材料参数。建模结果表明，基底位错的激活导致在张力下以 10-7s-1 的低应变速率在冰中发生脆性到韧性转变。在较高的应变速率下，冰固有的塑性各向异性导致晶粒间发生异质变形，晶界附近出现应力集中，从而引发裂纹萌生，加剧冰的脆性。在压缩下，裂纹通常不会在整个试样中扩展，因为在扩展时裂纹尖端周围的应力显着减少。此外，我们发现在冰层底部和沿冰川山谷侧面形成的剪切诱导基底结构加剧了冰的脆性。这项研究为冰的微观力学变形和断裂机制提供了见解，阐明了极地冰盖裂缝发展的复杂过程。