The metasurface is widely used in wave manipulation because it has an excellent capability of phase modulation in a simple way. In this work, we propose an elastic metasurface that can achieve retroreflection of a flexural wave on a thin metal plate. The elastic metasurface is composed of only two subunits with a simplified design. By carefully selecting the thickness and material of the subunits, the phase of flexural wave is re-modulated, and retroreflection is achieved at different incident angles. Furthermore, a single-phase metasurface and a two-component metasurface with fixed constraints and free boundaries, respectively, are studied. The results show that this type of elastic metasurface conveniently steers reflection of the flexural wave, and it may have potential applications in vibration control, energy harvesting, and piezoelectric sensors.

By assembling the square lattice arrays of “+” shaped steel rods, an underwater acoustic composite lens consisting of a convex lens and a slab lens is proposed to achieve the convergence of underwater acoustic waves. In order to study the focusing ability, numerical simulations and experiments in a silencing pool are carried out among a range of frequencies between 15 kHz and 25 kHz. As a result, the 3-D underwater acoustic wave focusing is inspiringly achieved and observed. Particularly, the proposed underwater acoustic composite lens is vertically extended from a 2-D convex lens, but it is found to be able to focus waves in a three-dimensional manner. Comparisons of wave intensities and the focal distance between the numerical results and experimental results show fair agreements. These findings pave the way to the usage of superlens, hyperlens, and Luneburg lens for 3-D underwater acoustic wave focusing.

The differential quadrature method has been developed to calculate the elastic band gaps from the Bragg reflection mechanism in periodic structures efficiently and accurately. However, there have been no reports that this method has been successfully used to calculate the band gaps of locally resonant structures. This is because, in the process of using this method to calculate the band gaps of locally resonant structures, the non-linear term of frequency exists in the matrix equation, which makes it impossible to solve the dispersion relationship by using the conventional matrix-partitioning method. Hence, an accurate and efficient numerical method is proposed to calculate the flexural band gap of a locally resonant beam, with the aim of improving the calculation accuracy and computational efficiency. The proposed method is based on the differential quadrature method, an unconventional matrix-partitioning method, and a variable substitution method. A convergence study and validation indicate that the method has a fast convergence rate and good accuracy. In addition, compared with the plane wave expansion method and the finite element method, the present method demonstrates high accuracy and computational efficiency. Moreover, the parametric analysis shows that the width of the 1st band gap can be widened by increasing the mass ratio or the stiffness ratio or decreasing the lattice constant. One can decrease the lower edge of the 1st band gap by increasing the mass ratio or decreasing the stiffness ratio. The band gap frequency range calculated by the Timoshenko beam theory is lower than that calculated by the Euler-Bernoulli beam theory. The research results in this paper may provide a reference for the vibration reduction of beams in mechanical or civil engineering fields.

In this paper, a 3D semi-analytical method is proposed by introducing the Durbin’s Laplace transform, as well as its numerical inversion method, state space approach and differential quadrature method to analyse the transient behaviour of functionally graded material cylindrical panels. Moreover, to investigate the effectiveness of the proposed semi-analytical solution, four boundary conditions are used to undertake the analyses. Comparing the proposed approach with other theoretical methods from the literatures, we see better agreements in the natural frequencies. Besides, the semi-analytical solution acquires nearly the same transient response as those obtained by ANSYS. Convergence studies indicate that the proposed method has a quick convergence rate with growing sample point numbers along the length direction, so do layer numbers increase along the radial direction. The effects of thickness/outer radius ratio, length/outer radius ratio and functionally graded indexes are also studied. When carbon nanotube is added to functionally graded material cylindrical panel, the composite structures have been reinforced greatly. The proposed 3D semi-analytical method has high accuracy for the analysis of composite structures. This study can serve as a foundation for solving more complicated environments such as fluid–structure interaction of flexible pipe or thermal effect analysis of functionally graded material in aerospace field.

Due to the development of gas and oil exploration into the deep sea, the effective tensile capacity provided by armored steel wire will decrease rapidly with the increase of the weight of umbilical cables. In this paper, two designs of lightweight umbilical cables were studied in full consideration of the geometric characteristics, and the mechanical properties were investigated under tension, bending, and torsion. The contact and friction between the components of the umbilical cables were also included in the model. Three cases are presented for validation from theoretical and finite element methods. The discussion on variables was carried out from the views of friction coefficient and helically wound angle. Compared with the steel tube umbilical model, the nonmetallic armored umbilical cable shows higher tensile strength and more flexibility. With the increase of friction coefficient, the stiffness of umbilical cable models don't change much. The helically wound angle has a great influence on the tensile stiffness and bending stiffness but little effect on the torsional rigidity. The proposed lightweight model can be applicable to 6000m water depth. This research can benefit the design of umbilical cables to achieve the goal of high tensile capacity in deepwater applications.

As a powerful modality for biomedical research, photoacoustic computed tomography (PACT) offers the combination of optical specificity and acoustic penetration for in vivo visualization. However, its performance is limited by a trade-off between ultrasound detection aperture and sensitivity, compromising image contrast, resolution, and penetration depth. Here, we introduce three-dimensional aperture-driven photoacoustic tomography (3D-ADPAT) to overcome these limitations, synergistically combining a high–numerical-aperture focused ultrasonic transducer (HNA-FUT) with a phase-inverted focusing-equivalent reconstruction (PIFER) algorithm. This approach yields ~2.21-fold enhancement in spatial resolution and ~10-fold increase in contrast-to-noise ratio. 3D-ADPAT’s performance was validated through comprehensive simulations and phantom studies and further confirmed by in vivo whole-body imaging that resolved deep-seated anatomies and tracked small-molecule metabolic pathways. Furthermore, a barrel-shaped array–based 3D-ADPAT implementation was designed, supporting dynamic imaging within a large field of view or across variable spatiotemporal scales. In summary, 3D-ADPAT provides a powerful tool for advanced photoacoustic systems, promising to accelerate frontier biomedical research.