Force amplification at the wheel hub due to the split in the air-cavity mode for a rolling tire

Reduction of tire/road noise has become an important issue for EV's since powertrain noise has largely been eliminated. A tire's air-cavity mode is known to be a significant contributor to increased forces at the wheel hub, which can result in significant interior noise levels near 200 Hz. Moreover, the single natural frequency of a static, undeformed tire can separate into two neighboring frequencies for a rolling, deformed tire due to the Doppler effect. In this study, the evolution of the frequency split at different speeds was observed in Tire Pavement Test Apparatus (TPTA) tests by measuring the dynamic force at the hub under rotation and load. Similar results were obtained using FE simulations to generate Campbell diagrams. Through the FE simulation, it has been shown that there can be force amplification at the hub when the split frequencies couple with adjacent treadband structural modes near 200 Hz. In addition, both material and geometrical modifications were applied to the base model to find values that would reduce force levels at the split frequencies. Finally, it is suggested that a target speed needs to be determined when evaluating a tire since the two natural frequencies are strongly influenced by rotation speed.