Triaxial compressive loading experiments were performed on columnar S2 saline ice, a plastically orthotropic material with planar isotropy normal to the columnar grains, to describe the effect of confinement on the strength and deformation of the material. Samples of columnar S2 saline ice were tested at −10°C under three types of triaxial loading—Proportional loading where the ratios of the normal stresses, applied along and across the columns, were varied in a systematic method; Conventional loading where the ice was confined under a constant hydrostatic pressure and then a uniaxial compressive load was applied perpendicular to the columns; And off-axis loading where proportional normal stresses were applied at an angle to the columns. In all three cases the nominal strain rate in the direction of greatest load was 4 × 10−5 s−1. At the given strain rate and temperature all samples deformed in a macroscopically ductile manner. The flow behavior was characterized by the yield and peak stresses, and the flow stress at 1% and 2% inelastic deformation. The yield and peak stresses rose with increasing across-column confinement, but were generally insensitive to along-column confinement. The flow stress showed a dependence on both the along- and across-column confinements at both 1% and 2% inelastic deformation. The ice behavior is discussed in terms of dislocation processes, cracking, grain boundary sliding and dynamic recrystallization. The yield and peak stresses agree with Hill's [1950] criterion at low to moderate confinements, but do not compare very well at higher confinements. It is then shown that alternative criterion by Horrigmoe and Zeng [1994] (modified) and Melton [1999] reasonably describe the data over a wider range of confinement. Correspondingly, the inelastic deformation generally obeys the associated flow rules.
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机译:在柱状S2盐冰上进行了三轴压缩载荷实验,该柱状冰是一种塑性正交异性材料,其平面各向同性垂直于柱状晶粒,以描述约束对材料强度和变形的影响。柱状S2盐冰样品是在-10°C的三种类型的三轴载荷下进行测试的-比例载荷,其中沿系统和沿柱施加的法向应力的比率以系统的方法变化;常规载荷,其中冰被限制在恒定的静水压力下,然后垂直于圆柱施加单轴压缩载荷。偏心载荷是在与圆柱体成一定角度的情况下施加成比例的法向应力。在这三种情况下,在最大载荷方向上的标称应变率为4×10 -5 super> s -1 super>。在给定的应变率和温度下,所有样品都以宏观延性方式变形。流动行为的特征在于屈服应力和峰值应力,以及在1%和2%的非弹性变形下的流动应力。屈服强度和峰值应力随跨柱约束的增加而增加,但通常对沿柱约束不敏感。在1%和2%的非弹性变形下,流动应力都显示出对沿柱和跨柱约束的依赖性。从位错过程,破裂,晶界滑动和动态再结晶等方面讨论了冰的行为。屈服强度和峰值应力在低至中度约束下与Hill(1950)的标准一致,但在较高约束下则无法很好地比较。然后表明,Horrigmoe和Zeng [1994](修改)和Melton [1999]的替代标准在更大范围内合理地描述了数据。相应地,非弹性变形通常遵守相关的流动规则。
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