Contact-Patch-Size Distribution and Limits of Self-Affinity in Contacts between Randomly Rough Surfaces
Contact-Patch-Size Distribution and Limits of Self-Affinity in Contacts between Randomly Rough Surfaces
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DOI：
10.3390/lubricants6040085
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发表时间：
2018-12-01
期刊：
影响因子：
3.5
通讯作者：
Wang, Anle
中科院分区：
文献类型：
--
作者：
Mueser, Martin H.;Wang, Anle
具有随机粗糙表面的固体之间的真正接触往往发生在大量的微观接触斑上。到目前为止，已经确定了两个缩放制度的数量密度n（A）的接触补丁大小A在弹性，非粘性，自仿射接触。在小的A处，n（A）近似为常数，而在大的A处，n（A）按幂律减小。利用绿色函数分子动力学，我们确定了一个特征（最大）接触面积A（c），如果接触压力低于接触膨胀的压力p（cp），则在该面积以上n（A）的超指数衰减变得明显。我们还发现，A（c）随着负载的增加相对缓慢远离接触渗流。A（c）的结果可以根据应力自相关函数G（sigma sigma）（r）估计，参数如下：特征接触片的半径r（c）不能太大，以至于G（sigma sigma）（r（c））远小于p（cp）（2）。我们的研究结果提供了一个可能的机制，在大的接触压力和/或具有较大的滚降波长的表面与负载之间的摩擦和磨损的比例故障。
True contact between solids with randomly rough surfaces tends to occur at a large number of microscopic contact patches. Thus far, two scaling regimes have been identified for the number density n(A) of contact-patch sizes A in elastic, non-adhesive, self-affine contacts. At small A, n(A) is approximately constant, while n(A) decreases as a power law at large A. Using Green's function molecular dynamics, we identify a characteristic (maximum) contact area A(c) above which a superexponential decay of n(A) becomes apparent if the contact pressure is below the pressure p(cp) at which contact percolates. We also find that A(c) increases with load relatively slowly far away from contact percolation. Results for A(c) can be estimated from the stress autocorrelation function G(sigma sigma)(r) with the following argument: the radius of characteristic contact patches, r(c), cannot be so large that G(sigma sigma)(r(c)) is much less than p(cp)(2). Our findings provide a possible mechanism for the breakdown of the proportionality between friction and wear with load at large contact pressures and/or for surfaces with a large roll-off wavelength.