Suzuki Kosuke, Hirai Yuji, Ohzono Takuya
Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Higashi, Tsukuba 305-8565, Japan.
ACS Appl Mater Interfaces. 2014 Jul 9;6(13):10121-31. doi: 10.1021/am5010738. Epub 2014 May 4.
Friction on soft materials is strongly correlated with the associated deformation, which may be controlled by the surface topography. We investigate the wearless sliding friction between a rigid hemispherical indenter and a deformable textured surface, which is shape-tunable wrinkles. The size of the indenter is comparable to the wavelength of the wrinkles. We evaluate the effects on the friction of the aspect ratio of the wrinkles, the applied normal load, and the alignment direction of the wrinkles relative to the sliding direction. The frictional oscillations are observed during sliding in the direction perpendicular to the alignment using optical images and friction profiles. The correlation of friction force oscillation with deformation of the wrinkles is elucidated using Hertz contact theory. Within a cycle of frictional oscillation, the friction force increases as the front part of the indenter elastically plows the crests. When the normal load is high and/or the aspect ratio of the wrinkles is low, the indenter continues to squash the wrinkles and remains in contact with them during sliding. Consequently, the amplitude of friction force oscillation relative to the averaged friction force decreases.
软材料上的摩擦与相关变形密切相关，而这种变形可能由表面形貌控制。我们研究了刚性半球形压头与可变形纹理表面（即形状可调的皱纹）之间的无磨损滑动摩擦。压头的尺寸与皱纹的波长相当。我们评估了皱纹的纵横比、施加的法向载荷以及皱纹相对于滑动方向的排列方向对摩擦的影响。在垂直于排列方向滑动过程中，利用光学图像和摩擦轮廓观察到了摩擦振荡。使用赫兹接触理论阐明了摩擦力振荡与皱纹变形之间的相关性。在摩擦振荡的一个周期内，随着压头前部弹性犁过波峰，摩擦力增大。当法向载荷较高和/或皱纹的纵横比较低时，压头在滑动过程中会持续挤压皱纹并与之保持接触。因此，相对于平均摩擦力，摩擦力振荡的幅度减小。
