A Root Cause of Curve Squeal: Self-Excited Frictional Vibration of a Wheelset-Track System

When a metro vehicle navigates a tight curve, it invariably causes a squealing noise. Most researchers proposed the negative friction-velocity slope as the generation mechanism for curve squeal. However, some phenomena of railway curve squeal are still difficult to explain. The purpose of this paper is to establish a friction-coupling finite element model of the wheelset-track system that can accurately predict curve squeal and to examine the influence of different wheelset-track structures on the trend of curve squeal occurrence. It has been proposed that curve squealing is caused by self-excited frictional vibrations. The complex eigenvalue analysis (CEA) and transient dynamics analysis were applied to predict the unstable vibration of curve squeal. The impacts of the coefficient of friction between the rail and the wheel, wheel web plate shape, fastener damping, gauge, and negative friction-velocity slope on the curve squealing noise were studied. The results demonstrated that the predicted frequency corresponded to the main frequency of the squealing noise measured on-site. Simultaneously, a friction coefficient of 0.25 or higher resulted in a curve squeal with a frequency of 2153.9 Hz. An S-shaped web plate wheel, appropriate fastener damping, and gauge can reduce unstable vibrations and curve squealing when a metro vehicle navigates a tight curve. The negative friction-velocity slope has less influence on the tendency of curve squealing.