Curve squeal on the Stockholm metro Statistical analysis based on data collected by an onboard monitoring system
Typ
Examensarbete för masterexamen
Program
Sound and vibration (MPSOV), MSc
Publicerad
2019
Författare
Swierkoska, Anna
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Curve squeal is a high level tonal noise that is generated during curving of rail
vehicles as a result of vibrations induced by the low rail (inner wheel) wheel–rail
contact. Due to its large magnitude tonal components typically in the range up to
10 kHz, squeal is regarded to be the most annoying noise generated by the railway
transport system. The mitigation of squeal noise is challenging and urgent as railway
networks are often located in densely populated areas and rail-bound transportation
is expected to become a backbone in the development of the future sustainable
transportation system.
The current study is based on noise data recorded by an onboard monitoring system
during one year of traffic on the green metro line of the Stockholm metro. The influence
of selected variables on the generation of curve squeal are investigated by a
statistical assessment performed in two steps; (1) a screening analysis accounting for
the entire green metro line with focus on variables related to track alignment (e.g.
curve radius and track constructed inside or outside of tunnels) and environmental
conditions (e.g. time of year and precipitation) and (2) a detailed analysis of the
conditions that promote squeal generation at two selected short radius curves exposed
to severe curve squeal. For the later a third-order logistic regression model is
developed with air temperature, humidity and vehicle speed as predictor variables.
The results clearly show the generation of curve squeal to become more frequent
with decreasing curve radius. For the two curves studied in the logistic regression
analysis, vehicle speed is found to be unimportant with respect to squeal generation.
In this part of the study only the coefficient related to humidity shows a significant
influence on the origin of curve squeal. The importance of environmental conditions
is further emphasised by the observation that the occurrence of curve squeal
decreases during precipitation.
Beskrivning
Ämne/nyckelord
Squeal noise, curve squeal, logistic regression