Experimental Study On Vibration And Acoustic Radiation Characteristics Of Railway Wheel With Damping Ring

Squeal noise from railway wheels occurring in sharp curves produces a very intense and highly annoying railway noise. The lateral creep of the wheels on the top of the rail is assumed to be the main mechanism leading to squeal noise. Additional systems can be added on the wheel in order to limit the acoustic emission, and one of the effective methods is to use wheels with metal rings inserted with a certain pre-load into grooves cut under the wheel rim. However, the effectiveness of these so called damping rings varies from one wheel to another, depending on the designs of the rings. In order to understand the causes of such differences, as well as factors that influence the reduction of noise from wheels with damping ring, sound radiation characteristics of a standard wheel and wheels with damping rings (damped wheels) of different designs were tested in a semi-anechoic room, followed by detail discussin.3D FE models are developed for the standard wheel that is taken to be a reference in this study for the damped wheels. Combining the eigen frequencies and modal shapes of the standard wheel calculated by the FE models and the frequency response functions of the standard wheel and those of the damped wheels tested in the lab, the noise reduction of the damped wheels is assessed and the reduction mechanisms are studied. By way of flexible suspension to make the wheels be in an approximately free state, the standard wheel is tested for its vibration and radiation characteritics. At the same time, tests are also performed for wheels with a metal ring of diameter 14mm, wheels with two metal rings of diameter 12mm and wheels with two metal rings of diameter 14mm, all under different pre-load conditions. From these tests the effect of the ring diameter and that of the pre-load are discussed. The effect of the number of rings is assessed using the ring of diameter 14 mm. Again, it is done by way of flexible suspension to make the wheels be in an approximately free state, and wheels with different number of the metal rings of diameter are tested 14mm under different pre-load conditions. The vibration and sound radiation characteristics of the standard wheel, a damped wheel with two 12mm metal rings and a damped wheel wth two 14mm metal rings were tested under two configurations:the first is that the wheels are in free condition and the second is that the wheels are in contact with a rail. A detailed discussion is made based on these tests. From what has been discussed above, we may safely draw the following conclusions:1. Damping rings have not significant influence on the modal frequencies of the wheel but can greatly increase its modal damping;2. Under both radial and axial excitations, the vibration and sound radiation of a ring-damped wheel is much reduced compared with the original wheel.3. Wheels with a single metal ring of diameter 14mm exhibits noise reduction as the the pre-load increase. However, as the pre-load increases further, nagetive effect will occur.4. If another ring is added, then noise reduction can be siginificantly increased;5. However, for wheels with two metal rings, change in ring diameter from 12mm to 14mm results in small change in noise radiaction;6. Two mechanisms of noise reduction with damping rings can be identified:friction between the ring and the wheel, and loca stiffness engancement by the ring.