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首页> 外文会议>Leeds-Lyon Symposium on Tribology; 19990914-17; Leeds(GB) >Some fundamental differences in the adhesion and friction of rough versus smooth surfaces
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Some fundamental differences in the adhesion and friction of rough versus smooth surfaces

机译：粗糙表面与光滑表面的附着力和摩擦力存在一些根本差异

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Recent Surface Forces Apparatus (SFA) experiments have shed new light on the roles of surface roughness and surface deformations, both at the molecular and microscopic scales, in determining adhesion and friction. Depending on the roughness, but also on other factors such as the stiffness and viscoelasticity of surfaces, these effects can cause the effective adhesion force to be orders of magnitude lower or higher than the thermodynamic (equilibrium) value, which in turn determines the frictional behaviour. The interactions of 'ideal', i.e., molecularly smooth, undamaged, surfaces are now quite well understood, both theoretically and experimentally. However, this is not the case for rough surfaces, which are difficult to define and characterize, and for which rigorous theories and reliable experimental data are lacking. Yet, most real or 'engineering' surfaces are rough on the nanometer to micrometer scale. This significantly affects their short-range interactions, their tribological behavior (adhesion, friction and lubrication) and their failure mechanisms (fracture and wear). Even when great care is taken to ensure smoothness, it is generally very difficult to produce a surface with a roughness of less than 25A except over small areas (usually for research purposes) and it is known that even a few nm of roughness can reduce the adhesion force between hard surfaces by more than an order of magnitude, and totally change their tribological behavior. To date there is no general theory for the interactions of rough surfaces nor any systematic experiments that identify the main trends; for example, how does the adhesion force or friction coefficient of a particular surface depend on its roughness? Indeed, one of the major problems is that roughness itself is not well defined. Simply quoting the RMS roughness of a surface is too simplistic, whereas describing it rigorously in terms of its Fourier components is too impractical. This whole issue has recently come to be appreciated as central to many tribological questions. We have recently performed measurements, using the SFA and scanning lateral probe techniques, on various surfaces having different roughness in an attempt to uncover some general trends and principles that describe the dependence of adhesion, friction and wear on roughness. We find, for example, that there is a generic, approximately exponential, relationship for the repulsive force between two rough surfaces, and that for non-adhering surfaces the friction force is proportional to the load (not the real contact area) at the molecular level. These and other, such as the dynamic, aspects of the tribological interactions between rough surfaces are described and discussed.
机译：最近的表面力装置（SFA）实验在分子和微观尺度上揭示了表面粗糙度和表面变形在确定粘附力和摩擦力方面的作用。根据粗糙度，还取决于其他因素（例如表面的刚度和粘弹性），这些影响可能导致有效粘附力比热力学（平衡）值低或高几个数量级，而热力学（平衡）值又决定了摩擦行为。从理论上和实验上，现在都已经很好地理解了“理想的”，即分子光滑，未损坏的表面之间的相互作用。但是，对于粗糙的表面却不是这种情况，粗糙的表面很难定义和表征，并且缺乏严格的理论和可靠的实验数据。但是，大多数真实或“工程”表面在纳米到微米级上都是粗糙的。这极大地影响了它们的短程相互作用，摩擦学行为（粘附，摩擦和润滑）以及破坏机理（断裂和磨损）。即使非常注意确保光滑度，通常也很难生产出粗糙度小于25A的表面，除非是在较小的区域（通常用于研究目的），而且众所周知，即使只有几nm的粗糙度也可以减小表面粗糙度。硬表面之间的附着力超过一个数量级，并完全改变了它们的摩擦学行为。迄今为止，还没有关于粗糙表面相互作用的通用理论，也没有确定主要趋势的系统实验；例如，特定表面的粘附力或摩擦系数如何取决于其粗糙度？确实，主要问题之一是粗糙度本身没有很好地定义。简单地引用一个表面的RMS粗糙度太简单了，而就其傅立叶分量严格地描述它太不切实际了。最近，整个问题被视为许多摩擦学问题的核心。我们最近使用SFA和扫描侧向探针技术在具有不同粗糙度的各种表面上进行了测量，以试图揭示一些描述粘合，摩擦和磨损对粗糙度的依赖性的一般趋势和原理。例如，我们发现两个粗糙表面之间的排斥力存在一般的近似指数关系，而对于非粘附表面，摩擦力与分子上的载荷（不是实际接触面积）成正比水平。描述和讨论了粗糙表面之间摩擦相互作用的这些和其他方面，例如动态方面。

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