Wheel-rail squeal noise during train turning has been a tricky problem influencing passengers and nearby residents. The tonal curve squeal that mainly occurs at the inner rail has been extensively studied, while the broadband flange squeal that takes place at the outer rail that can be equally annoying is seldom mentioned and hardly investigated. This paper presents a study aiming at understanding the mechanism of wheel-rail flange squeal from phenomenon to the underlying source. The study systematically demonstrates the connection between the observed wheel-rail flange squeal noise and contact force, with measurements taken from a series of well-controlled in-situ experiments on an operating metro line, and numerical simulations. An integrated transient model consisting of three submodels on train dynamics, rail dynamics, and wheel-rail contact incorporating genuine 3D surface irregularities is developed specifically for flange squeal analysis. The developed model can reproduce the characteristics of flange squeal and correlates wheel-rail contact force with the flange squeal noise with satisfactory performance. Features of flange squeal under four-speed levels corresponding to in-situ experiments are reappeared from global dynamics to local contact status. An explanation of the generation mechanism of flange squeal is proposed by measurement observation and confirmed through the proposed model with multiple influencing key factors, including train speed, contact position, shape of contact patch, contact creepages, and wheel and rail irregularities. The present study is expected to establish a footstone for the mechanism comprehension of flange squeal and inspire further research in this area.

火车转弯时的轮轨尖叫声一直是影响乘客和附近居民的棘手问题。主要发生在内轨处的音调曲线啸叫已被广泛研究，而在外轨处发生的同样令人讨厌的宽带法兰啸叫却很少被提及，也几乎没有被研究过。本文提出了一项研究，旨在从现象到潜在来源了解轮轨法兰尖叫的机制。该研究系统地展示了观察到的轮轨法兰尖叫噪声与接触力之间的联系，测量结果来自在运营的地铁线路上进行的一系列控制良好的现场实验，以及数值模拟。一个集成的瞬态模型，由列车动力学、轨道动力学、结合真正的 3D 表面不规则性的轮轨接触是专门为法兰啸叫分析而开发的。所开发的模型可以再现法兰啸叫的特征，并将轮轨接触力与法兰啸叫相关联，具有令人满意的性能。从全局动力学到局部接触状态，再现了原位实验对应的四速水平下的法兰尖啸特征。通过测量观察提出了法兰尖啸产生机理的解释，并通过所提出的模型确认了该模型，该模型具有多个影响关键因素，包括列车速度、接触位置、接触面形状、接触爬电距离以及轮轨不平整度。