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Design, Analysis, and Testing of a Metamaterial Vibration Isolator for Hydrophone Equipped on Autonomous Underwater Vehicles

Yang Yuhan, Sun Qindong, Xu Shangfeng, Sun Tongshuai, Zhao Haitong, Yang Shaoqiong

Polish Maritime Research

2025

nr 1

121--128

The acoustic detection performance of hydrophones on the acoustic characteristics of targets is highly sensitive to external vibrations and noise interference. With the limitations of volume within autonomous underwater vehicles (AUVs) and highly corrosive ocean environments, the design of an embedded vibration isolator (VI) is needed so as to protect the hydrophones equipped on AUVs. To effectively isolate the low-frequency vibration produced by actuators on the AUV, such as the thruster, rudder, etc., this paper designs a VI for a hydrophone equipped on the AUV by using a metamaterial with quasi-zero stiffness (QZS) characteristics. This VI contains circumferential vibration-damping units, which improve the overall vibration damping effect through integration with the radial multi-stage damping layers. As a result, by utilising harmonic response analysis, the conformal design of eight circumferential units and two radial layers is optimised across all designs; its maximum vibration transmissibility is 56 dB at 500 Hz. Finally, the effectiveness of the QZS VI is verified through an experiment, which also shows a good match with the trend of the simulation results. This work also provides theoretical guidance for further study on the optimisation of phononic crystal mechanisms for vibration damping.

Kinetic characterization of adolescent scoliosis patients with Lenke 1B+

Wang Huai, Fu Rongchang, Yang Kewei

Acta of Bioengineering and Biomechanics

2024

Vol. 26, no. 3

75--86

The purpose of this study was to investigate dynamic responses of Lenke1B+ spines of adolescent scoliosis patients to different frequencies. Methods: Modal analysis, harmonic response analysis and transient dynamics of a full spine model inverted by the finite element method using Abaqus. Results: The first-order axial resonance frequency of 4.51 Hz produced a maximum axial displacement of 30.15 mm. Comparison of the five frequencies indicated that the 10 Hz frequency response curve was smoothest, while the amplitudefrequency curve at 4 Hz showed the greatest fluctuations accompanied by resonance phenomena. At the resonance frequency, the maximum axial displacement of the thoracic spine was at T1, being 31.17 mm, while that of the lumbar spine was at L1, with 0.56 mm. The maximum stress of the intervertebral discs was located between T4 and T5, representing 3.496 MPa, the maximum stress in the small joints was located in the concavity between T7 and T8, with 19.97 MPa and the maximum axial displacement was 54.31 mm, located in the convexity between T6 and T7. Conclusions: The first-order axial resonance frequency was the most harmful to the patient. The uneven stress distribution in the spine was closely related to the degree of spinal deformity, with the thoracic spine being more sensitive to low frequencies than the lumbar spine. The concave side of the spinal deformity was more prone to stress concentrations while the convex side was more prone to deformity, indicating that disc degeneration and small-joint disease are more likely to occur at the most deformed part of the spine.