Chemical Creep and Its Effect on Contact Aging
Chemical Creep and Its Effect on Contact Aging
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DOI：
10.1021/acsmaterialslett.2c00356
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发表时间：
2022-06
影响因子：
11.4
通讯作者：
Zhuohan Li;I. Szlufarska
中科院分区：
文献类型：
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作者：
Zhuohan Li;I. Szlufarska
材料的年龄，以及它们的特性可以随着时间尺度的演变，在许多情况下，可以在实验室实验中捕捉到。蠕变是最常见的老化现象之一，其基本机制通常涉及在外加应力下的连续塑性变形或扩散。在弹性区域和室温下，典型固体不会发生随时间变化的变形，除非材料是粘弹性的。在这里，我们进行了多尺度模拟，发现在没有塑性、扩散或粘弹性的情况下，固体材料之间的粗糙接触可以发生变形蠕变，从而导致接触面积的时间演化。当材料界面是反应性的时，这种蠕变就会发生，它是由于粘性界面化学键的连续形成，从而将表面拉向彼此。这些化学键不仅增加了接触面积，而且提高了摩擦接触的剪切强度，对摩擦接触的老化有协同作用，静摩擦随接触时间的延长而增大。我们的工作提供了一种新的接触蠕变机制，并进一步揭示了接触老化不仅源于“接触量”─接触面积─的增加，而且还源于“接触质量”─剪切强度─，更重要的是，这两种机制并不一定相互独立。
Materials age, and their properties can evolve over time scales that in many cases can be captured in laboratory experiments. Creep is one of the most commonly observed aging phenomena, and the underlying mechanisms typically involve continuous plastic deformation or diffusion under the applied stress. In the elastic regime and at room temperature, time-dependent deformation is not expected in typical solids, unless the material is viscoelastic. Here, we performed multiscale simulations and discovered that deformation creep and, thus, time evolution of the contact area can occur at asperity contact between solid materials in the absence of plasticity, diffusion, or viscoelasticity. This creep takes place when the material interface is reactive, and it arises from the successive formation of adhesive interfacial chemical bonds that pull the surfaces toward each other. Those chemical bonds not only increase the contact area but also enhance the shear strength, resulting in a synergic effect on aging of frictional contacts, where the static friction increases with the contact time. Our work provides a new contact creep mechanism and, furthermore, reveals that contact aging can originate from not just the increase in the “contact quantity”─contact area─but also from the “contact quality” ─shear strength─and more importantly, the two mechanisms are not necessarily independent of each other.