A number of authors have experimentally assessed the influence of friction on adhesive contacts, and generally the contact area has been found to decrease due to tangential shear stresses at the interface. The decrease is however generally much smaller than that predicted already by the Savkoor and Briggs 1977 classical theory using “brittle” fracture mechanics mixed mode model extending the JKR (Griffith like) solution to the contact problem. The Savkoor and Briggs theory has two strong assumptions, namely that (i) shear tractions are also singular at the interface, whereas they have been found to follow a rather constant distribution, and that (ii) no dissipation occurs in the contact. While assumption (ii) has been extensively discussed in the Literature the role of assumption (i) remained unclear. We show that assuming entirely reversible slip at the interface with a constant shear stress fracture mechanics model leads to results almost indistinguishable from the Savkoor and Briggs model (and further in disagreement with experiments), hence it is assumption (ii) that critically affects the results. We analyze a large set of experimental data from Literature and show that the degree of irreversibility of friction can vary by orders of magnitude, despite similar materials and geometries, depending on the velocity at which the tangential load is applied.

中文翻译：

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剪切式软胶触点的摩擦不可逆度

许多作者已经通过实验评估了摩擦对粘合剂接触的影响，并且通常发现接触面积由于界面处的切向切应力而减小。但是，这种减小通常比Savkoor和Briggs 1977年使用“脆性”断裂力学混合模式模型将JKR（类似于格里菲斯）解决方案扩展到接触问题的经典理论所预测的要小得多。Savkoor和Briggs理论有两个很强的假设，即（i）剪力在界面处也是奇异的，而已发现它们遵循相当恒定的分布，并且（ii）接触中不发生耗散。尽管在文献中对假设（ii）进行了广泛讨论，但假设（i）的作用仍不清楚。我们表明，假设采用恒定剪应力断裂力学模型在界面处完全可逆滑动，将导致结果与Savkoor和Briggs模型几乎无法区分（并且进一步与实验不一致），因此，假设（ii）对结果有重大影响。我们分析了来自文献的大量实验数据，结果表明，尽管材料和几何形状相似，但摩擦的不可逆程度可能会因数量级变化而变化，具体取决于切向载荷施加的速度。