The interfacial contact conditions between a railway vehicle wheel and the rail are paramount to the lifespan, safety and smooth operation of any rail network. The wheel–rail interface contact pressure and area conditions have been estimated, calculated and simulated by industry and academia for many years, but a method of accurately measuring dynamic contact conditions has yet to be realised. Methods using pressure-sensitive films and controlled air flow have been employed, but both are limited. Ultrasonic reflectometry is the term given to active ultrasonics in which an ultrasonic transducer is mounted on the outer surface of a component and a sound wave is generated. This ultrasonic wave packet propagates through the host medium and reflects off the contacting interface of interest. The reflected waveform is then detected and contact area and interfacial stiffness information can be extracted from the signal using the quasi-static spring model. Stiffness can be related to contact pressure by performing a simple calibration procedure. Previous contact pressure measurement work has relied on using a focusing transducer and a two-dimensional scanning arrangement which results in a high-resolution image of the wheel–rail contact, but is limited to static loading of a specimen cut from a wheel and rail. The work described in this paper has assessed the feasibility of measuring a dynamic wheel–rail contact patch using an array of 64 ultrasonic elements mounted in the rail. Each element is individually pulsed in sequence to build up a linear cross-sectional pressure profile measurement of the interface. These cross-sectional, line measurements are then processed and collated resulting in a two-dimensional contact pressure profile. Measurements have been taken at different speeds and loads.

中文翻译：

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用于静态和动态测量轮轨接触压力和面积的超声波阵列评估

铁路车辆车轮和钢轨之间的界面接触条件对任何铁路网络的寿命、安全性和平稳运行至关重要。工业界和学术界对轮轨界面接触压力和面积状况进行了多年的估计、计算和模拟，但尚未实现准确测量动态接触状况的方法。已经采用了使用压敏薄膜和受控气流的方法，但两者都受到限制。超声波反射计是对有源超声波的术语，其中超声波换能器安装在部件的外表面上并产生声波。该超声波包通过宿主介质传播并从感兴趣的接触界面反射。然后检测反射波形，并使用准静态弹簧模型从信号中提取接触面积和界面刚度信息。通过执行简单的校准程序，刚度可以与接触压力相关联。以前的接触压力测量工作依赖于使用聚焦换能器和二维扫描装置，这会产生轮轨接触的高分辨率图像，但仅限于从轮轨上切割的试样的静态载荷。本文中描述的工作评估了使用安装在轨道上的 64 个超声波元件阵列测量动态轮轨接触面的可行性。每个元件都按顺序单独脉冲，以建立界面的线性横截面压力分布测量值。这些横截面，然后对线测量进行处理和整理，从而产生二维接触压力分布。在不同的速度和负载下进行了测量。