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 EVs 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 combination of the tire’s asymmetry, and the Doppler effect resulting from the tire’s rotation. In this study, the evolution of the Doppler-related frequency split with increasing speed 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. 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, material modifications were applied to the base model in the simulations 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 split, natural frequencies are strongly influenced by rotation speed.