A Laboratory Procedure for Measuring the Dispersion Characteristics of Loaded Tires

It is of interest to be able to measure the wave dispersion characteristics of tires, since that information can be used to identify the types and speeds of waves propagating within them. The latter information can be used, for example, to identify the waves that preferentially radiate sound or create structure-borne disturbances that can propagate into the vehicle interior. This type of measurement is usually performed by driving an unloaded tire at one point on its treadband with a shaker, and then measuring the resulting radial vibration around the tire circumference by using a laser vibrometer. The latter spatial data can then be Fourier transformed, one frequency at-a-time, to reveal the tire’s dispersion characteristics. However, it is well known that loading a tire has a significant impact on its dynamic response, causing circumferential modes of both the carcass and interior air space to split, for example. In this paper, the design and construction of an experimental rig that allows dispersion measurements to be made on a loaded tire will be described. Here, the focus was on relatively low frequencies, so the rig was designed to be dynamically rigid below 300 Hz