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 in situ 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 in situ at the interface; values in the range of 0.22 to 0.61 were measured for different surface configurations.

中文翻译：

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使用超声波响应测量界面摩擦

滑动表面之间的摩擦是工程的许多方面普遍存在的基本现象。有许多滑动接触摩擦计可以测量实验室环境中的摩擦力。然而，将实验室数据传输到真实机器元件是不可靠的。结果取决于试样配置、表面状况和环境。在这项工作中，开发了一种方法，该方法使用高功率超声波的非线性响应来推断界面处的原位摩擦系数。当高功率横波撞击摩擦界面时，会发生相对滑动。它施加非线性响应并导致在接收的超声信号中产生高阶奇数频率分量。谐波的幅度取决于接触应力和局部摩擦系数。已经通过数值和实验研究了这种非线性超声响应。一个简单的一维模型已被用于预测非线性的产生。该模型已与在增加负载下压在一起的铝粗糙表面上进行的实验进行了比较。已经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。已经证明可以在界面处原位确定摩擦系数；对于不同的表面配置，测量了 0.22 到 0.61 范围内的值。该模型已与在增加负载下压在一起的铝粗糙表面上进行的实验进行了比较。已经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。已经证明可以在界面处原位确定摩擦系数；对于不同的表面配置，测量了 0.22 到 0.61 范围内的值。该模型已与在增加负载下压在一起的铝粗糙表面上进行的实验进行了比较。已经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。已经证明可以在界面处原位确定摩擦系数；对于不同的表面配置，测量了 0.22 到 0.61 范围内的值。