Case study of fastener clip failure in small-radius curve track by field test and numerical simulation

Abstract

Recurrent failures of rail fastener clips have been increasingly observed at a small-radius curve section of a Hong Kong metro line, compromising operational safety of the train. To illustrate the underlying mechanisms, this study adopts a two-pronged methodology that integrates field measurements with numerical simulations. Firstly, wheel-track resonance characteristics are systematically investigated using friction-induced self-excitation vibration theory coupled with synchronised field measurements of rail vibration and corrugation. To characterise the clip's modal parameters, a refined finite element (FE) model validated by on-site modal tests is developed, revealing that clip natural frequencies at 560 Hz and 1050 Hz are directly matching dominant wheel-track excitation frequency bandwidths of 500–600 Hz and 1000–1200 Hz. Secondly, we propose a novel framework to efficiently calculate the clip fatigue damage in frequency domain. It utilises the power spectral density (PSD) function of rail acceleration and clip stress in the track system, significantly reducing the FE model scale and enhancing the simulation-measurement correlation. The principal findings indicate: (1) The concentrated stress of the gauge-side clips is 13 % higher than the outer-side clips of the clip; (2) The fatigue failure rates of inner rail gauge-side clips is at least 4.7 times higher than that of other positions; and (3) Critical fracture initiation points are situated at the root of the rear arch's inner surface. These results closely correspond with field observations, validating the practical engineering value of the proposed methodology for dynamic fatigue damage assessment.