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In this paper, an intelligent prediction and design method of acoustic metamaterial beams based on deep learning is presented. A theoretical model of acoustic metamaterial beams is derived by using the spectral element method to calculate the band structure and transmission characteristic of beam-type acoustic metamaterial. A high-degree-of-freedom design space dataset of band structure and transmission characteristics is constructed. In addition, the vibration transmission characteristics of acoustic metamaterial beams are predicted and the on-demand inverse design of acoustic metamaterial beams is realized by constructing a fully connected deep learning neural network model. Furthermore, the forward prediction and reverse design network model is verified by using the autoencoder neural network model. Results show that the predicted value of the autoencoder neural network structure is in good agreement with the target value, which indicates the feasibility of the intelligent design method of acoustic metamaterials based on deep learning. The presented intelligent design method could be potentially utilized in the field of fast and efficient acoustic metamaterial design for low frequency vibration isolation in engineering structures. [ABSTRACT FROM AUTHOR]

Sandwich structures are widely applied in modern industry such as aerospace, automobile as well as marine structures. However, the vibroacoustic properties of sandwich structures are adversely influenced by low effective mass. In this study, the flexural wave propagation characteristics and vibration mitigation performances of the periodic sandwich plate-type metastructures are investigated. The proposed sandwich plate-type metastructures are constituted of a sandwich plate with periodic thin-wall circular tube cores and periodically attached local stepped resonators. A finite element method combining Solid-Shell coupling numerical method and Bloch theory is presented to calculate the dispersion relations and the displacement fields of the eigenmodes of the infinite periodic sandwich plate-type metastructures. In addition, the acceleration frequency responses and vibration attenuation performances of finite periodic sandwich plate-type metastructures are numerically investigated and compared with the experimental measurements. Furthermore, the influences of geometric parameters on flexural wave band gaps are conducted. Results show that the sandwich plate-type metastructures can yield a low-frequency broad flexural wave band gap, in which the flexural wave propagation is conspicuously suppressed, resulting in significant flexural vibration attenuation. The flexural wave band gap and vibration attenuation performances can be effectively manipulated by designing geometric parameters of the sandwich plate-type metastructures. [ABSTRACT FROM AUTHOR]

In this paper, the wave propagation mechanics theoretical model of hull grillage metastructures with local resonators is established, and the intelligent design method of hull grillage metastructures is proposed based on deep learning. The flexural vibration isolation characteristics of periodic hull grillage structures and the proposed hull grillage metastructures are theoretically studied using the spectral element method. Numerical calculation and experimental tests of the flexural wave vibration transmission of hull grillage metastructures are conducted to validate the proposed theoretical model. In addition, the data set is constructed by using the wave mechanics theoretical model of hull grillage metastructures, and the forward prediction neural network model of vibration transmission characteristics as well as the inverse design neural network model of hull grillage metastructures are established. Results show that compared with periodic hull grillage structures, the proposed hull grillage metastructures possess significant low-frequency flexural wave vibration isolation characteristics which almost completely covers the low-frequency range from 27 Hz to 169 Hz. Both forward prediction and inverse design network models have good performance, which verifies the correctness of the intelligent design method based on deep learning, and provides a new direction for the structural design on demand of low-frequency vibration reduction of ship and offshore structures. • The wave propagation theoretical model of hull grillage metastructures is established. • The flexural vibration isolation characteristics are studied by using the spectral element method. • Numerical calculation and experimental tests are conducted to validate the theoretical model. • The intelligent design method of hull grillage metastructures is proposed based on deep learning. [ABSTRACT FROM AUTHOR]

Elastic metamaterial is a type of artificial composite material/structure with unique subwavelength physics property, which shows attractive potential application in low-frequency sound and vibration control. In this paper, a ship vibration isolation method using the band gap concept of sandwich plate-type elastic metastructures is proposed to solve the low frequency vibration and noise control of marine power system. The flexural wave propagation and low-frequency vibration isolation characteristics of sandwich plate-type elastic metamaterials are investigated by using the finite element method combination with Solid-Shell multi-physics coupling model and Bloch theory. Numerical results demonstrate that the proposed sandwich plate-type elastic metastructures possess significant low-frequency subwavelength flexural wave band-gap and vibration isolation characteristics under the premise of structural strength and stiffness. The formation mechanism of flexural band gap is mainly attributed to the mode coupling of the local resonant mode and the Lamb wave mode of sandwich plate. The experimental measurements of flexural vibration transmission spectra were conducted to validate the accuracy and reliability of the numerical calculation method. In addition, the influences of geometrical parameters on the flexural wave band gap are studied. On this basis, the potential application of the proposed ship vibration isolation method in the marine power system is explored. • A ship vibration isolation method using the band gap concept is proposed. • The dispersion relations are calculated by using Solid-Shell multi-physics coupling model. • The experimental measurements of flexural vibration transmission spectra were conducted. • The potential application of ship vibration isolation method in the marine power system is explored. [ABSTRACT FROM AUTHOR]