Transfer Path Analysis and Low-Frequency Vibration Reduction by Locally Resonant Phononic Crystal

The motor has vibration characteristics of order and multi-band in the frequency domain, which is different from the internal combustion engine when it is used as the vehicle’s drive. These characteristics cannot be briefly attenuated by general methods, but make the phononic crystal (PC) an ideal solution to eliminate the vibration transmission of the motor, because the concentrated vibration peak can easily be blocked by the bandgap. In this paper, one dimensional locally resonant phononic crystal (LRPC) which has low-frequency bandgaps are arranged on the automotive subframe to absorbing vibration. The partial coherence analysis is used to analyze the transfer characteristic of vibration on the subframe. Then, 6 main paths are selected from the 18 vibration transmission paths, based on its high ratio of partial coherence coefficient in a certain frequency, and the arranged position, the spring stiffness and the resonator’s mass of the LRPCs are chosen based on this result. An experiment of a one-dimensional LRPC beam was used to calculate the transfer function. The results show that the theoretical calculation, finite element simulation and experimental bandgap are consistent. Finally, the transfer functions of the subframe are calculated by the finite element method. By comparing the two cases whether with or without LRPCs, the results show that after optimization, better vibration attenuation can be achieved under the premise of small mass increase. This result provides a new method for low-frequency vibration reduction of electric vehicles.