Berg S, Johannsmann D
Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
Phys Rev Lett. 2003 Oct 3;91(14):145505. doi: 10.1103/PhysRevLett.91.145505.
Quartz resonators in contact with metal-covered spheres have been used to study the tribology of micron-sized metal-metal contacts at high speed (1 m/sec and high frequency (12 MHz), while maintaining a shear amplitude in the nanometer range. The data aquisition is based on ring-down experiments, where the electrical excitation is periodically interrupted and the free decay of the oscillation is analyzed. At contact, an amplitude-dependent frequency and decay rate are found, indicative of an underlying nonlinear equation of motion. Using perturbation theory and the two-timing approximation, a nonlinear spring constant kappa(1)(x) and a nonlinear drag coefficient xi(1)(x) are explicitly derived. We find a local slip-to-stick-transition at a shear amplitude of 0.5 nm. Coating the gold sufaces with a self-assembled thiol monolayer removes the stick.
与金属包覆球体接触的石英谐振器已被用于研究微米级金属-金属接触在高速（1米/秒）和高频（12兆赫兹）下的摩擦学，同时保持纳米范围内的剪切振幅。数据采集基于衰荡实验，其中电激励被周期性中断，并分析振荡的自由衰减。在接触时，发现了与振幅相关的频率和衰减率，这表明存在一个潜在的非线性运动方程。使用微扰理论和双时近似，明确推导了非线性弹簧常数κ(1)(x)和非线性阻力系数ξ(1)(x)。我们发现在0.5纳米的剪切振幅处存在局部滑-粘转变。用自组装硫醇单分子层涂覆金表面可消除粘连。
