We study the frictional behavior of both elastic and viscoelastic thin coatings bonded to a seemingly rigid substrate and sliding against a rough profile in the presence of Coulomb friction at the interface. The aim is to explore the effect of the coupling between the normal and tangential displacement fields arising from the finiteness of the material thickness and to quantify the contribution this can have on energy losses.

We found that, due to normal–tangential coupling, asymmetric contacts and consequently additional friction are observed even for purely elastic layers, indeed associated with zero bulk energy dissipation. Furthermore, enhanced viscoelastic friction is reported in the case of viscoelastic coatings due to coupling, this time also entailing larger bulk energy dissipation.

Geometric coupling also introduces additional interactions involving the larger scales normal displacements, which leads to a significant increase of the contact area, under given normal load, compared to the uncoupled contacts.

These results show that, in the case of contact interfaces involving thin deformable coating bonded to significantly stiffer substrate, the effect of interfacial shear stresses on the frictional and contact behavior cannot be neglected.

我们研究了弹性和粘弹性薄涂层的摩擦行为，这些涂层粘结到一个看似刚性的基底上，并且在界面处存在库仑摩擦的情况下在粗糙轮廓上滑动。目的是探索由材料厚度的有限性引起的法向和切向位移场之间耦合的影响，并量化其对能量损失的贡献。

我们发现，由于法向-切向耦合，即使对于纯弹性层，也观察到不对称接触并因此观察到额外的摩擦，实际上与零体积能量耗散有关。此外，据报道，由于偶联，在粘弹性涂层的情况下粘弹性摩擦增强，这一次也导致更大的体积能耗散。

几何耦合还引入了涉及较大尺度法向位移的其他相互作用，与未耦合的触头相比，在给定的法向载荷下，这导致接触面积显着增加。

这些结果表明，在接触界面涉及粘结到明显较硬的基材上的薄的可变形涂层的情况下，界面剪切应力对摩擦和接触行为的影响不可忽略。