The Role of the Third Deviatoric Stress Invariant in the Creep of Ice

对实验室和冰川现场测量的冰变形数据的分析，加上初步的双向蠕变实验，表明应力结构(作用于应变率测量方向以外的应力)对冰变形速率的影响可能比Glenn流动定律所建议的要大得多。这项研究将在威斯康星河瀑布大学的冷实验室中进行，包括在简单剪切和同时压缩的简单剪切中制备冰。这些实验将检验格伦流动定律的准确性，该定律假定在描述双轴应力下冰的变形时独立于第三不变量。如有必要，结果应允许将流动定律修改为基于第二种和第三种变体的更一般形式。这项研究的第二部分将涉及对冰川冰样进行联合应力测试，展示出广泛的晶体组构和颗粒尺寸，以研究各向异性冰流动规律的形式。

Analysis of ice deformation data from laboratories and from field measurements on glaciers, coupled with preliminary biaxial creep experiments, suggest that stress configuration (stresses acting in directions other that the direction in which the strain rate is measured) may effect the deformation rate of ice much more than that suggested by Glenn's Flow Law. This study will involve prepared ice in simple shear and in simple shear with simultaneous compression in a cold laboratory at the University of Wisconsin- River Falls. These experiments will test the accuracy of Glen's Flow Law, which assumes independence from the third invariant in describing deformation of ice under biaxial stresses. Results should allow, if necessary, modification of the flow law to a more general form based on both the second and third variants. A second part of this study will involve conducting combined stress tests on glacier ice samples exhibiting a broad range of crystal fabrics and grain sizes to investigate the form of the flow law for anisotropic ice.