A case study of railway curve squeal radiated from both the outer and inner wheel

• A comprehensive case study is presented that studies curve squeal on a 213 m radius metro curve based on measurements performed both trackside and on-board passing vehicles. • Wayside noise measurements show squeal noise emission with an intermittent character that contains discrete jumps between dominating 1/3 octave bands with centre frequencies in the range between 6.3–15.8 kHz. This is significantly higher as compared to the main body of field measurements presented in literature. • On-board noise measurements taken close to the wheel–rail contacts of an instrumented wheelset show tonal squeal generated from the outer wheel with similar noise characteristics as typically related to inner wheel squeal. • Analysis of long-term on-board noise measurement data containing almost 2000 vehicle passages indicate squeal radiation from the inner and outer wheel of the instrumented wheelset for 65 % and 8 % of vehicle passages, respectively. Further, the occurrence of curve squeal radiated from the inner wheel was found to increase by 10 % after rail grinding. This case study is presented after observations were made that partially contrast the prevailing picture of railway curve squeal given in the literature. These are observations with significance both for modelling and condition monitoring. The current case study will be followed by a subsequent investigation focused on the validation and application of a simulation model to investigate root-causes for curve squeal at the Stockholm metro. Curve squeal in a 213 m radius curve on the Stockholm metro is studied. Data includes track characteristics (rail profile, rail roughness and gauge width) and noise measured at the trackside as well as by two vehicles equipped with an on-board mounted noise monitoring system. The current case study contrasts field measurements of curve squeal reported in the literature by a relative shift of emitted noise towards higher frequencies. Wayside noise measurements in the studied curve during a few hours showed squeal generation for all vehicle passages with dominating 1/3 octave band centre frequencies in the range between 6.3–15.8 kHz. Noise data measured during one year of regular traffic of two vehicles equipped with a monitoring system were obtained. The occurrence of curve squeal was analysed through an implementation of the curve squeal detection algorithm in operation at the Stockholm metro. This algorithm was also applied to search for events of squeal noise radiation from the outer wheel. Results show emissions of squeal noise from the inner and outer wheel for 65 % and 8 % of the vehicle passages through the studied curve, respectively. Further, the occurrence of curve squeal radiated from the inner wheel was found to increase by 10 % after rail grinding. In the literature, squeal radiated from the outer wheel is described as having an intermittent character with magnified spectral components in the frequency range between 5–10 kHz. In contrast, the current work presents sustained tonal squeal generated from the outer wheel with similar noise characteristics as typically related to ordinary curve squeal.