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首页> 外文期刊>Journal of Materials Research >Nanoindentation creep of quartz, with implications for rate- and state-variable friction laws relevant to earthquake mechanics
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Nanoindentation creep of quartz, with implications for rate- and state-variable friction laws relevant to earthquake mechanics

机译：石英的纳米压痕蠕变，对与地震力学有关的速率和状态变量摩擦定律有影响

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摘要

The frictional behavior of rocks in the laboratory is reasonably well described by rate-and state-variable friction laws, which reproduce a rich variety of natural phenomena when used in models of earthquakes. Despite the widespread adoption of the rate and state formalism in earthquake mechanics, the physical mechanisms that occur at microscopic contacting asperities on the sliding surface, which give rise to the observed rate and state effects, are still poorly understood. In an attempt to identify these underlying mechanisms, a series of nanoindentation experiments on quartz, an abundant mineral in the earth's crust, was conducted. These experiments demonstrate the utility of using continuous stiffness measurements as a means of obtaining reliable indentation creep data on hard materials like quartz at room temperature. The projected area of indentation in quartz increases linearly with the logarithm of the time of indentation, in agreement with the increase in real area of contact with log time inferred from slide-hold-slide friction experiments on quartz rocks. However, the increase in fractional area with time in the indentation tests was larger than that inferred from friction experiments by a factor of 1.7. Differences between the rates of fractional area increase in the two tests may indicate that the increase in contact area during the hold portion of slide-hold-slide tests was modulated by slip that occurs during reloading after the hold, as was observed for other materials. The nanoindentation results suggest that the increase in frictional strength (i.e., the increase of state in the rate- and state-variable friction laws) during slide-hold-slide friction experiments was caused by creep of the highly stressed asperity contacts.
机译：速率和状态变量摩擦定律可以很好地描述实验室中岩石的摩擦行为，当在地震模型中使用时，该定律可再现多种自然现象。尽管在地震力学中普遍采用了速率和状态形式主义，但对在滑动表面上的微观接触粗糙处发生的物理机制（导致观察到的速率和状态效应）的了解仍然很少。为了确定这些潜在的机理，对石英进行了一系列纳米压痕实验，石英是地壳中的一种丰富矿物。这些实验证明了使用连续刚度测量作为在室温下获得诸如石英等硬质材料的可靠压痕蠕变数据的手段的实用性。石英的压痕投影面积随压痕时间的对数线性增加，这与从石英岩石上的滑动-保持-滑动摩擦实验得出的实际接触面积与对数时间的增加一致。但是，压痕测试中的分数面积随时间的增加比摩擦实验推断的要大1.7倍。两次测试中分数面积增加率之间的差异可能表明，在滑动保持式滑动测试的保持部分期间，接触面积的增加受到保持后重新加载过程中发生的滑动的调节，正如其他材料所观察到的那样。纳米压痕结果表明，在滑动-保持-滑动摩擦实验期间，摩擦强度的增加（即，速率和状态变量摩擦定律中状态的增加）是由高应力粗糙接触的蠕变引起的。

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