Micromechanics of sea ice frictional slip from test basin scale experiments.
Micromechanics of sea ice frictional slip from test basin scale experiments.
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试验盆规模实验中海冰摩擦滑移的微观力学。
DOI：
10.1098/rsta.2015.0354
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Sammonds PR
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作者：
Sammonds PR
我们在环境试验池中对大型浮盐水浮冰进行了一系列高分辨率的摩擦实验。在这些实验中，一个中心浮冰被推到另外两个浮冰之间，沿着两个界面断层滑动。摩擦运动主要是粘滑运动。沿滑动断层测量了剪切应力、正应力、局部应变和滑动位移，并监测了声发射。在沿断层的几个位置进行的单个粘滑循环的高分辨率测量使我们能够确定摩擦滑动的两个阶段：成核阶段，在此阶段，成核区在断层的其余部分之前开始滑动，以及整个断层滑动的传播阶段。这是滑移弱化行为。因此，我们已经描述了我们认为是北冰洋动力学中的关键变形机制。为了理解海冰摩擦的微观力学，我们采用了一个理论本构关系（即在温度、法向载荷、加速度、速度和滑移位移方面的剪切应力方程），该本构关系来源于粗糙-粗糙接触和滑动的物理学（Hatton et al. 2009 Phil.）。ma89, 2771-2799 (doi: 10.1080/14786430903113769))。在引入滑移弱化后，我们的实验数据与这一摩擦规律较为吻合。研究发现，本构关系遵循Archard定律而非Amontons定律，其中τ为剪切应力，σ n为正应力，n= 26/27，具有分形粗糙度分布，其中摩擦剪切应力，τ= f分形T ml ws，其中f分形为分形粗糙度高度分布，T ml为摩擦熔化和润滑的剪切强度，ws为滑移减弱。因此，我们可以推断，在这些实验条件下，界面断层的剪切破坏是通过剪切脆性破坏的过程，以及在更高的速度下，通过摩擦加热、局部表面熔化和流体动力润滑的过程。本文是“冰的微动力学”主题的一部分。
We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick–slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick–slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (ie an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity–asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89, 2771–2799 (doi: 10.1080/14786430903113769)). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with (where τ is the shear stress and σ n is the normal stress) and n= 26/27, with a fractal asperity distribution, where the frictional shear stress, τ= f fractal T ml ws, where f fractal is the fractal asperity height distribution, T ml is the shear strength for frictional melting and lubrication and ws is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities, through frictional heating, localized surface melting and hydrodynamic lubrication. This article is part of the themed issue ‘Microdynamics of ice’.