Geometry effects on the vibro-acoustic behavior of railway resilient wheels

Noise generated by railway vehicles is nowadays one of the most important concerns in the railway engineering community and sometimes becomes one of the key points in the discussions preceding the design of a new line. Many researchers have contributed to achieve important improvements in the reduction of railway wheel noise during recent years. One of the solutions effectively able to reduce rolling noise is the adoption of resilient wheels, nowadays widely used on city trams and sometimes on high-speed trains. Some studies have shown the important role played by the wheel rubber blocks in reducing rolling noise and a strict link between their stiffness and the emitted noise has been demonstrated as well. On the other hand the resilient wheel effectiveness in mitigating squeal noise has not yet been deeply investigated. Moreover the effects of factors, different from the rubber block features, have not been completely stated. The aim of the present paper is to analyze which are the main parameters affecting the resilient wheel vibro-acoustic behavior and the consequences on squeal noise emission. This study considers not only the rubber block features but also other parameters, such as wheel geometry. The research approach is both experimental and numerical. The analysis has been carried out up to 5 kHz. Two different resilient wheels have been tested performing modal analyses and getting sound pressure levels at the same time. The results have been compared and commented. It has been found that the wheel geometry plays an important role in determining the wheel vibro-acoustic behavior, although rubber blocks remain the most influent elements. Particularly the wheel width value has significant effects on the tread dynamics and, as the main consequence, on the wheel sound radiation.