A Physics-Based Rock Friction Constitutive Law: Steady State Friction
A Physics-Based Rock Friction Constitutive Law: Steady State Friction
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DOI：
10.1002/2016jb013829
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发表时间：
2018-02-01
影响因子：
3.9
通讯作者：
Scholz, Christopher H.
中科院分区：
文献类型：
--
作者：
Aharonov, Einat;Scholz, Christopher H.
在很宽的滑动速度范围内测量摩擦的实验发现，摩擦系数的值变化很大：摩擦是高的，在缓慢滑动的速率和状态本构关系的行为，但显着减弱的滑动速度接近地震滑动速度。我们引入一个基于物理的理论来解释这种行为。使用传统的蠕变微观物理学，我们计算的速度和温度依赖性的接触应力在滑动过程中，包括剪切加热的热效应。假设接触达到耦合的热和机械稳定状态，并计算摩擦稳定滑动。理论计算结果与实验结果吻合较好，石英和花岗岩的摩擦速度超过11个数量级。新模型阐明了摩擦的物理学原理，并预测了摩擦定律与独立确定的材料参数之间的联系。它预测了四个摩擦机制作为滑移率的函数：在低速摩擦是速度增强或减弱，这取决于材料参数，并遵循速率和状态摩擦定律。表面和体积活化能之间的差异是速度依赖性的主要控制。在中等速度下，对于某些材料参数，出现了明显的速度强化区。在快速滑动时，剪切加热产生摩擦的热软化。在最快的滑动，融化导致进一步削弱。该理论的四个摩擦区域与先前发表的低温和正应力下的实验结果吻合得很好。简明语言摘要在大范围滑动速度下测量摩擦的实验发现，摩擦系数的值变化很大：在缓慢滑动时摩擦系数很高，但当滑动速度上升到地震滑动速率时，摩擦系数明显减弱。我们引入一个基于物理的理论来解释这种行为。我们的模型假设摩擦力是由滑动面之间接触处的蠕变控制的。它还假设，当滑动是快速接触加热，这影响摩擦深刻。我们的模型是能够定量预测，第一次，在所有实验测量的滑移率的稳态摩擦的实验结果报告。这是使用从其他实验中测量的与摩擦无关的材料参数来完成的。新模型可能对理解摩擦力，特别是地震物理学有深远的影响。
Experiments measuring friction over a wide range of sliding velocities find that the value of the friction coefficient varies widely: friction is high and behaves according to the rate and state constitutive law during slow sliding, yet markedly weakens as the sliding velocity approaches seismic slip speeds. We introduce a physics-based theory to explain this behavior. Using conventional microphysics of creep, we calculate the velocity and temperature dependence of contact stresses during sliding, including the thermal effects of shear heating. Contacts are assumed to reach a coupled thermal and mechanical steady state, and friction is calculated for steady sliding. Results from theory provide good quantitative agreement with reported experimental results for quartz and granite friction over 11 orders of magnitude in velocity. The new model elucidates the physics of friction and predicts the connection between friction laws to independently determined material parameters. It predicts four frictional regimes as function of slip rate: at slow velocity friction is either velocity strengthening or weakening, depending on material parameters, and follows the rate and state friction law. Differences between surface and volume activation energies are the main control on velocity dependence. At intermediate velocity, for some material parameters, a distinct velocity strengthening regime emerges. At fast sliding, shear heating produces thermal softening of friction. At the fastest sliding, melting causes further weakening. This theory, with its four frictional regimes, fits well previously published experimental results under low temperature and normal stress.Plain Language Summary Experiments measuring friction over a wide range of sliding velocities find that the value of the friction coefficient varies widely: friction is high during slow sliding, yet markedly weakens as the sliding velocity rises to seismic slip rates. We introduce a physics-based theory to explain this behavior. Our model assumes friction is controlled by creep at contacts that form between the sliding surfaces. It also assumes that when sliding is fast contacts heat up, and this affects friction profoundly. Our model is able to quantitatively predict, for the first time, reported experimental results for steady state friction at all experimentally measured slip rates. This is done using material parameters that are measured from other experiments, unrelated to friction. The new model may have far reaching implications for understanding friction in general and for earthquake physics in particular.