Page 199 - 《摩擦学学报》2021年第6期

984 摩 擦 学 学 报 第 41 卷

influence on the electrical signal. As for the current signal in the friction process, when the two friction pairs contacted
and separated continuously, the current signal presented a bipolar signal. However, the difference of the friction mode
led to the possibility that the peak shape of the current in the friction process may appear bipolar signals, or it may be
unipolar. This special phenomenon was explained by analyzing the electron flow at its rubbing interface. The large
interfacial potential difference of the interface caused by triboelectrification and the transfer of the third body made it
possible for a large amount of static charge from the surface to re-inject to the metal surface. Because the third body
participated in the friction process of the interface, the triboelectric properties of the interface were changed. The transfer
of materials and the induction of the electrical polarity of the interface made the triboelectric potential showed a
nonlinear trend during the friction process. That was, the surface potential of PTFE showed a reverse evolution trend
after reaching the maximum value. Further experiments showed that this phenomenon of reverse evolution of surface
potential existed when steel balls and steel sheets rubbed against PTFE. Optical photographs and surface element
analysis of metal friction proved that there were physically adsorbed wear debris and an incompletely covered transfer
film with irregular shapes on the surface of the metal friction pair. During the friction process of steel-PTFE, the reversal
time of potential can be corresponded to the time when the friction coefficient entered the stable stage, which was of
great value to realize the in-situ monitoring of the friction pair motion and fault warning in the process of mechanical
motion. This study proposed the mechanism of the triboelectric non-monotonic change of steel-PTFE, and links the start
time of stable friction coefficient with the reversal time of surface potential, which has potential application of friction
monitoring of steel-PTFE or other metal-polymer friction. It is foreseeable that in the future tribology, coupling the
triboelectricity of the interface or other test methods into the traditional friction test system is the trend of online
monitoring of the friction state and the state of the friction pair.
Key words: steel-PTFE; triboelectrification; surface potential; current; polarity evolution; friction monitor

作为一种对界面状态十分敏感的摩擦物理现象， 在金属-聚合物配副的摩擦中，可以通过测量金属端
摩擦起电常被用于摩擦副界面接触状态和性质变化 的接地电流和聚合物的表面电势实现对其界面摩擦
检测的辅助分析手段 [1-4] . 目前，摩擦起电被普遍认为 起电行为的测量 [35-38] ，这也为利用界面的摩擦电信号
是由两接触-分离表面的电子云发生重叠导致的电子 变化原位反映摩擦和磨损状态提供了可行的途径.
转移造成的 [5-7] ，而在有水参与的界面中，双电层的存 本文作者利用摩擦试验机和电学测试系统的耦
在使得离子转移成为影响摩擦起电性能的重要因素 [8-11] . 联，实现了对钢-PTFE摩擦副摩擦运动过程中的摩擦
另外，在摩擦过程中材料的转移也会导致摩擦起电性 系数、接地电流和摩擦电势三种信号的原位收集. 通
能发生改变 [12-16] . 与简单的接触-分离起电相比，摩擦 过分析这三种信号之间的内在联系，研究了钢-PTFE
起电更加复杂，摩擦副在摩擦过程中产生的机械互 配副的摩擦起电行为. 研究发现，在摩擦过程中这三
锁、磨损和界面物质转移等现象极大地影响了材料间 种信号的变化存在正相关性，证明了摩擦副的摩擦学
的摩擦起电行为. 行为与其摩擦起电行为之间存在内源性联系，这为实
通常两个物体相互摩擦时，两种材料的原子核对 现摩擦副摩擦状态的智能监测提供了新思路.

其核外电子的束缚能力差异越大，越容易起电. 作为
1 试验部分
一种常见的摩擦配副，金属与聚合物摩擦时，聚合物
材料极易得/失电子而在表面富集大量静电，进而影响 1.1 试验材料及制备
材料的摩擦和磨损等性能，因此其摩擦起电行为在应 商用纯PTFE块(φ20 mm×8 mm)购自上海金优橡
[17]
用过程中备受关注 . 除了材料的本性，摩擦副材料 塑制品厂，试验前分别用200目、400目和800目的砂纸
的摩擦起电还受材料表面结构、化学组成、摩擦运动 对PTFE表面进行抛光，用无水乙醇清洗表面并在100 ℃
方式和外部环境条件等因素的制约 [11, 18-23] ，如可以通 的烘箱内热处理2 h. 轴承钢球(GCr15)购自宁阳新新
过载流或施加电场的方式对摩擦过程进行一定程度 球业，试验之前用丙酮和无水乙醇进行反复清洗，去
的调控 [24-27] . 另外，界面的接触应力和黏附状态等也会 除表面的有机物.

对材料的摩擦起电行为产生重大影响 [28-32] . 另一方面， 1.2 试验方法
通过对材料或摩擦过程中的电学和声学等信号的测 试验使用商用的TRB摩擦试验机(TRB3，Austria)
量可以有效地监测摩擦以及摩擦副的状态 [33-34] . 尤其 的旋转模块进行摩擦试验. 整个摩擦试验机通过铝箔