Meixia Chen

Engineering experience shows that in noise and vibration control for ships and aircraft, measures like stiffening can reduce vibration but may fail to lower radiated noise, as they disrupt structural continuity and create new radiation sources. This paper investigates the sub-critical frequency sound radiation from the boundaries of semi-infinite plates using analytical and discrete Fourier transform methods. A force-excited finite plate is also considered, generating its supersonic sound intensity map. Results demonstrate that the near- and far-field sound pressure and supersonic sound intensity manifest the radiation patterns of different boundary conditions as monopole, dipole, and quadruple pole patterns. At resonance, boundary acoustic radiation dominates in finite structures. Furthermore, as the plate size and frequency increase, the radiation differences among various boundary conditions converge to the results observed in semi-infinite plates. This study provides a mechanistic understanding of the relationship between vibration and sound radiation, offering valuable insights for controlling sound radiation in engineering applications.

Recent years have witnessed increasing research interest in metamaterials for vibration and noise control, with broadband vibration suppression being particularly sought after. This study proposes an analytical approach for achieving broadband vibration attenuation through parameter detuning of metamaterial plates. Through modal-based homogenization, energy method, and finite element validation, the effects of parameter detuning are quantitatively studied to obtain a vibration suppression scheme of metamaterial plates under Gaussian distribution. The plate’s average vibration response serves as a metric for evaluating suppression effectiveness across multiple samples. Results show while detuning reduces distinct band gap effect, it enables vibration suppression over a wider frequency range. Since parameter detuning naturally occurs in real manufacturing processes, considering it in the design is crucial for achieving effective broadband vibration control in practical applications.

A novel friction model for water-lubricated bearings under boundary lubrication conditions is proposed. The effects of speed, load, surface roughness, and material properties on the friction coefficient are examined. The model is validated through experimental tests using nitrile-butadiene rubber (NBR) and ultrahigh molecular weight polyethylene (UHMWPE) materials, demonstrating reliability and applicability. The impact of varying speed and load on lubrication regimes is analyzed, with a focus on the behavior of micro-convex contact friction under boundary lubrication conditions. Based on the verified friction model, the influence of surface roughness and texture direction on bearing performance is also explored, offering actionable insights for optimizing bearing design. This model provides critical insights for enhancing friction management and noise reduction in water-lubricated bearings, offering valuable guidance for their design and manufacturing.

The presence of excessive background noise in hydrodynamic noise experiments conducted in circulating water tunnels can significantly impact the accuracy and reliability of experimental test results. To address this issue, it is crucial to evaluate and optimize the background noise during the design stage. In this research, acoustic field model and fluid–solid coupling numerical calculation model of circulating water tunnels are established. Utilizing the finite element method, we analyze the flow noise and flow-excited noise resulting from wall pressure pulses in the circulating water tunnel. Furthermore, we conduct a noise contribution analysis and explore strategies for structural vibration noise control. The results demonstrate that both flow noise and flow-excited noise decrease with increasing frequency, with flow-excited noise being the primary component of the tunnel’s background noise. The presence of resonant peaks significantly contributes to the elevated flow-excited noise levels. Moreover, enhancing structural stiffness and damping proves less effective in suppressing low-frequency peaks. Additionally, employing sound measurement pods suspended from the side of the test section for noise measurement exhibits a high error rate at low frequencies. This research provides insights into optimizing background noise in water tunnels, thereby informing future enhancements in tunnel design.