Li X, Dwyer-Joyce R S
Leonardo Centre for Tribology, The University of Sheffield, Sheffield, UK.
Proc Math Phys Eng Sci. 2020 Sep;476(2241):20200283. doi: 10.1098/rspa.2020.0283. Epub 2020 Sep 30.
Friction between sliding surfaces is a fundamental phenomenon prevalent in many aspects of engineering. There are many sliding contact tribometers that measure friction force in a laboratory environment. However, the transfer of laboratory data to real machine elements is unreliable. Results depend on the specimen configuration, surface condition and environment. In this work, a method has been developed that uses the nonlinear response of a high-power ultrasonic wave to deduce friction coefficient at an interface. When the high-power shear wave strikes a frictional interface, relative slip can occur. It imposes a nonlinear response and causes generation of higher-order odd frequency components in received ultrasonic signals. The amplitude of the harmonics depends on contact stress and local friction coefficient. This nonlinear ultrasonic response has been investigated both numerically and experimentally. A simple one-dimensional model has been used to predict nonlinearity generation. This model has been compared with experiments conducted on aluminium rough surfaces pressed together under increasing loads. Two strategies have been used to estimate the friction coefficient by correlating experimental and numerical third-order nonlinearity. It has proved possible to determine the friction coefficient at the interface; values in the range of 0.22 to 0.61 were measured for different surface configurations.
滑动表面之间的摩擦是工程诸多方面普遍存在的一种基本现象。有许多滑动接触摩擦计可在实验室环境中测量摩擦力。然而，将实验室数据转换到实际机器部件上是不可靠的。结果取决于试样配置、表面状况和环境。在这项工作中，已开发出一种方法，该方法利用高功率超声波的非线性响应来推导界面处的摩擦系数。当高功率剪切波撞击摩擦界面时，可能会发生相对滑动。这会产生非线性响应，并导致在接收到的超声信号中产生高阶奇次频率分量。谐波的幅度取决于接触应力和局部摩擦系数。已通过数值和实验对这种非线性超声响应进行了研究。已使用一个简单的一维模型来预测非线性的产生。该模型已与在增加载荷下挤压在一起的铝粗糙表面上进行的实验进行了比较。已使用两种策略通过关联实验和数值三阶非线性来估计摩擦系数。已证明可以确定界面处的摩擦系数；针对不同的表面配置测量到的值在0.22至0.61范围内。
