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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Deformation of polycrystalline D2O ice: Its sensitivity to temperature and strain-rate as an analogue for terrestrial ice
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Deformation of polycrystalline D2O ice: Its sensitivity to temperature and strain-rate as an analogue for terrestrial ice

机译：多晶D2O冰的变形：其对温度和应变率的敏感性作为陆地冰的类似物

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摘要

Polycrystalline deuterated ice (D2O) was deformed over a range of high-temperatures (-20 to -1 degrees C; 0.92-0.99T(m)) during in situ neutron diffraction texture and grain-size analysis. This allowed for a continuous monitoring of the evolution of rheology, texture, grain-numbers and the type of microstructures, which are compared to those encountered in basal sections of ice-sheets. We quantify the textural evolution with J-index changes as a function of strain-rate and temperature. Three sets of unconfined samples were deformed at displacement rates of 1 x 10(-5) s(-1) (fast) 2.5 x 10(-6) s(-1) (medium) and 6 x 10(-7) s(-1) (slow). Dislocation creep is proposed as the main deformation mechanism with sub-grain rotation more significant at lower temperatures (0.92T(m)) and/or higher strain-rates. At higher-temperatures (0.99T(m)) and/or lower strain-rates dynamic recrystallization is dominated by grain boundary migration, typified by grains with highly curved or lobate grain boundaries, and leading to rheological softening of the ice. From initially randomly oriented [c]-axes, a texture comprising 30-35 degrees cones parallel to the compression axis develops, which is comparable to textures observed in the upper levels of polar ice-sheets. There is also a strain-rate dependence on the development of normalized [c] axis intensities, which is in competition with strain magnitude and temperature. At lower temperatures (<= 10 degrees C), small increments of strain or slower strain-rates, the cone-angle and textural strength decrease with a dominant textural component parallel to the compression axis. This may be an explanation for the vertical [c]-axis concentrations observed in polar ice cores. (C) 2019 Elsevier B.V. All rights reserved.
机译：在原位中子衍射纹理和晶粒尺寸分析期间，多晶氘代冰（D2O）在一定高度高温（-20至-1摄氏度; 0.92-0.99t（m））中变形。这允许连续监测流变学，质地，粒度和微观结构类型的演变，这与冰盖的基底部分中遇到的那些相比。我们用J-Index的函数量量化了J-Index的态度变化，作为应变速率和温度的函数。以1×10（ - 5）（-1）（快速）2.5×10（-6）S（-1）（中）和6×10（-7）S的位移速率以置换率变形三组无凝集样品。 （-1）（慢）。脱位蠕变被提出为具有亚粒转向的主要变形机制，在较低温度下更显着（0.92t（m））和/或更高的应变率。在较高温度（0.99t（m））和/或较低的应变率的动态重结晶是由晶界迁移的主导，由具有高弯曲或裂解晶界的晶粒键化，并导致冰的流变软化。从最初随机定向的[C] - 轴，纹理包括与压缩轴平行的30-35度锥体，其显影，其与在极性冰片的上层观察到的纹理相当。还存在对归一化[C]轴强度的发展的应变率依赖性，这是应变幅度和温度的竞争。在较低温度（<= 10℃）下，应变或较慢的应变率的较小增量，锥角和纹理强度随着与压缩轴平行的主要纹理部件而减小。这可能是在极地冰芯中观察到的垂直[c]轴浓度的解释。 （c）2019 Elsevier B.v.保留所有权利。

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