With the transformation of the trend of vehicle electrification, the overall noise level in the vehicle is gradually reduced. The problem of low-frequency noise in the vehicle, which was previously ignored, is becoming more and more prominent. To solve the vehicle low-frequency noise problem, a combination of real-vehicle tests and simulation analysis is carried out. During the test, the driver and passengers feel that there is a relatively obvious low-frequency roar noise in the car, which results from the structural radiation noise of the trunk door vibration. Therefore, to solve this problem, we design an acoustic metamaterial with lightweight and miniaturized features based on the local resonance principle of phononic crystals. Firstly, the selection of the resonant unit configuration and the design of the band gap are implemented. Then, the layout planning of the whole vehicle, the layout of the resonance unit and the design of the base frame are implemented. The actual vehicle test results show that: after attaching the designed acoustic metamaterial, the low-frequency noise sound pressure levels in the front and rear of the vehicle were reduced by 2.0 dB (A) and 2.3 dB (A), respectively, meanwhile, the interior noise sound quality was improved. The sound pressure level at the driver’s right ear in the car has an abnormal peak of around 35Hz. In addition, the driver and passengers feel that there is a relatively obvious low-frequency roar noise in the car, and through low-pass filtering of the collected signals, it is confirmed that the peak frequency is the main cause of the low-frequency roar in the car. The low-frequency steady-state noise of the car is generally considered to be the low-frequency vibration of the body panel and the radiation occurs. Through the finite element simulation analysis (Grid Participation Analysis) of the abnormal peak frequency, the results show that the low-frequency roar is caused by the low-frequency vibration of the tailgate sheet metal, and the problem peak frequency is not coupled with the acoustic cavity mode. Facing the problem of the low-frequency roar radiated into the car by the vibration of the tailgate sheet metal parts, based on the local resonance band gap theory, we developed a design to suppress the 35 Hz vibration of the tailgate sheet metal parts and meet the characteristics of lightweight and miniaturization. By attaching the acoustic metamaterial to the tailgate and performing CAE simulation of the whole vehicle, it is determined that the structure can indeed reduce the 35 Hz noise in the car and the peak value of the tailgate sheet metal vibration.

In this work, eco-friendly superhydrophobic coatings were prepared by dispersing hydrophobic silica nanoparticles and a waterborne silicone-modified polyurethane dispersion into an ethanol solution, which was free of fluorine and volatile toxic solvents. The effects of the silica content on the hydrophobicity and scratch resistance of the hydrophobic surfaces were investigated by WCA measurements and a sandpaper abrasion test, respectively. The experimental results indicated that when the silica content exceeded 30% by mass, the silica/silicone-modified polyurethane coatings had superhydrophobicity. Meanwhile, the superhydrophobic coatings with a silica content of 30% by mass simultaneously had the optimal mechanical stability. We studied the morphology and roughness of the hydrophobic surfaces with different silica content and attempted to briefly explain the influence mechanism of silica content. Furthermore, anti-icing and oil–water separation experiments were carried out on the superhydrophobic coatings, which exhibited good anti-icing performance and high separation efficiency. The eco-friendly superhydrophobic coating is expected to be applied in the fields of oil–water separation, anti-icing, and self-cleaning, etc.

To study the lateral and vertical vibration performance of high-speed EMU power wheelset axle box, the vehicle-track system dynamics models were established in SIMPACK software. The wheelsets structures were considered as rigid bodies and flexible bodies respectively in the dynamics models. The vehicles ran in straight line at speeds of 200, 250, 300, 350, and 400km/h respectively in the simulation, and the maximum vibration acceleration in lateral and vertical and the acceleration's root mean square value at different speed were got. The results show as follows: The lateral vibration acceleration of the non-leading wheelset is larger than the one of the leading wheelset. The vertical acceleration of the non-leading wheelset doesn't appear to be much different from the one of the leading wheelset. The ratio of the axle-box lateral vibration acceleration's root mean square value of the non-leading wheelset to the leading wheelset is 1.38, and the ratio of the maximum lateral vibration acceleration of the non-leading wheelset to the leading wheelset is 1.37 if the wheelsets are supposed to be rigid bodies and the vehicle runs at a speed of 350km/h. As speed increases, the difference of axle-box vibration acceleration in vertical and lateral between rigid wheelset and flexible wheelset increases, too. The ratio of the axle-box lateral vibration acceleration's root mean square value of the flexible wheelset to the rigid wheelset is 1.55 and the ratio of the axle-box maximum lateral vibration acceleration of the flexible wheelset to the rigid wheelset is 1.44 when the vehicle runs at a speed of 400km/h. The 1^st symmetric bending mode has the most impact on both the vertical and lateral vibration acceleration.