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The paper presents a semi-analytical method, named the Double Legendre Polynomial Method (DLPM), which is extended for modeling the axisymmetric free vibration of a functionally graded piezoelectric (FGP) hollow cylinder resonator. The FGP resonator is composed of two-phase graded piezoelectric materials, Lead zirconate titanate (PZT4) and aluminum nitrid (AlN), on the top and bottom surfaces, respectively, where the material properties gradually change along the thickness direction. The integration of FGP materials with piezoelectric materials is an innovative aspect in material science, and this paper explores their dynamic behavior, providing insights into their mechanical and electrical properties and contributes to expand our understanding of the axisymmetric free vibration of FGP hollow cylinder resonators as a crucial factor for optimizing their performance across a wide range of applications, including sensors, actuators, energy harvesting, and structural health monitoring systems. The DLPM is applied to solve the wave governing differential equations of motion, offering a new tool for studying the dynamic behavior of FGP hollow cylinders under axisymmetric vibration. The study investigates the effects of the diameter-thickness ratio on the effective electromechanical coupling coefficient and the resonant and anti-resonant frequencies of the FGP hollow cylinder. The results show that as the diameter-thickness ratio increases, the frequency-diameter product appears to become more stable. This observation is a valuable insight for optimizing the design of these resonators. Furthermore, the study presents the electrical input admittance, the natural frequencies as well as the mechanical displacement and electric potential profiles of the resonator. All the provided results are based on the calculation of the resonant frequencies. The validity of the presented results was verified by the comparison with the existing ones reported in the literature. [ABSTRACT FROM AUTHOR]

The materials industry is under increasing pressure to enhance performance while lowering costs and environmental impact. Three layers of functionally graded materials (FGMs) were proposed as a solution to this problem. The general goal of this research is to develop a semi-analytical method for solving the free vibration problem of FGMs in an infinite-length composite cylinder made of stainless steel (SS) and silicon nitride (SN). The formulation is based on Legendre polynomial approach and the use of specific rectangle window functions. This approach will result in an eigenvalue/eigenvector issue in the computation of normalized frequencies and displacement profiles. The effective material properties of FGM cylinders vary following the radial direction in conformity with the power-law distribution of the volume fractions. The numerical iteration approach was generated to create data utilizing MATLAB apps to investigate the free vibration analysis from specified boundary conditions. The results are obtained for longitudinal, torsional, and flexural modes. Then, the propagation of guided waves in three-layers (SN/SS/SN) of functionally graded cylinder with diverse gradient for each mode is studied. Accordingly, the results obtained demonstrate that the volumetric fraction of the FGM cylinder is significantly impacted by the graded-index. In addition, the graded-index has a major influence on the variation of the material's properties in the radial direction. Furthermore, the dispersion curves of the normalized frequencies and phase velocities are significantly influenced by the graded-index. These results demonstrate that the phase velocities of the same mode increase as the exponents of the power-law increase. The displacement distributions are also explored to better understand the characteristics of the guiding waves inside the materials. Furthermore, the boundary conditions have a more significant influence on the normal stresses. High accuracy is found between our results and those published in the literature (error = 0.58%). This paper provides an important insight into the propagation of ultrasonic-guided waves in functionally graded multilayer cylindrical constructs for non-destructive testing. [ABSTRACT FROM AUTHOR]

Due to the limit of preparation technology, defects, such as cracks and inclusions, are inevitable in the functionally graded quasi‐crystal material. For the purpose of the guided wave non‐destructive testing on the functionally graded (FG) two‐dimensional(2‐D) hexagonal quasi‐crystal(QC) plates, Lamb and SH wave characteristics in the context of the Bak's model are investigated by means of the Legendre polynomial method. The convergence of the polynomial method applied on the FG 2‐D hexagonal QC plate is analyzed. Some new wave characteristics resulted from the phonon‐phason coupling effect are revealed. There are three Lamb‐like modes without cut‐off frequencies for the x‐y and y‐z QC plates, but four Lamb‐like modes without cut‐off frequencies for the x‐z QC plate. For phonon modes, phonon displacements and stresses are bigger than phason displacements and stresses. However, they are just opposite for phason modes. It can be utilized to distinguish phonon modes and phason modes. [ABSTRACT FROM AUTHOR]