Browsing by Subject "Ultrasonic guided waves"

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Open Access
Design and finite element simulation of a novel 3D-CMUT device for simultaneous sensing of in-plane and out-of-plane displacements of ultrasonic guided waves
(MDPI AG, 2023-10-25) Zhang, S.; Lu, W.; Wang, A.; Hao, G.; Wang, R.; Yilmaz, Mehmet
In this study, we introduce a physical model of a three-dimensional (3D) guided wave sensor called 3D-CMUT, which is based on capacitive micro-machined ultrasonic transducers (CMUTs). This 3D-CMUT sensor is designed to effectively and simultaneously obtain 3D vibration information about ultrasonic guided waves in the out-of-plane (z-direction) and in-plane (x and y-directions). The basic unit of the 3D-CMUT is much smaller than the wavelength of the guided waves and consists of two orthogonal comb-like CMUT cells and one piston-type CMUT cell. These cells are used to sense displacement signals in the x, y, and z-directions. To ensure proper functioning of the 3D-CMUT unit, the resonant frequencies of the three composed cells are set to be identical by adjusting the microstructural parameters appropriately. Moreover, the same sensitivity in the x, y, and z-directions is theoretically achieved by tuning the amplification parameters in the external circuit. We establish a transient analysis model of the 3D-CMUT using COMSOL finite element simulation software to confirm its ability to sense multimode ultrasonic guided waves, including A0, S0, and SH0 modes. Additionally, we simulate the ball drop impact acoustic emission signal on a plate to demonstrate that the 3D-CMUT can not only utilize in-plane information for positioning but also out-of-plane information. The proposed 3D-CMUT holds significant potential for applications in the field of structural health monitoring (SHM).
Open Access
In-plane-sensing analysis of comb-like capacitive micro-machined ultrasonic transducers (cmuts) using analytical small-signal model and fem
(Institute of Electrical and Electronics Engineers, 2023-04-18) Zhang, S.; Lu, W.; Yang, Y.; Wang, R.; Zhang, G.; Xu, B.; Yılmaz, Metin; Zhang, W.
In this work, capacitive micro-machined ultrasonic transducers (CMUTs) were developed into comb-like shapes to make these comb-like shaped structures work for sensing in-plane vibrations of ultrasonic guided waves. On this basis, an analytical small-signal model, which is mainly a combination of the forced vibration theory and the simplified parallel-plate capacitor model, was proposed to satisfy the requirements of theoretical design. Through the proposed model, the in-plane-sensing behaviors of a comb-like CMUT cell can be predicted, including vibrating velocity, output current, and sensitivity. Compared with the results calculated from the finite element method (FEM) simulation, it was found that the static state and the frequency-domain results of the analytical small-signal model agree well with those of FEM simulations if the used first natural frequencies of these two methods are identical. Considering the fringing field capacitance could further improve the accuracy of the analytical small-signal model. At last, influences of some external parameters, i.e., dc bias voltage, air damping, and input in-plane displacement, on the sensitivity of a comb-like CMUT cell were discussed by the analytical small-signal model and FEM simulation. Relevant results reveal the way to design a comb-like CMUT and indicate the conditions when the analytical small-signal model is accurate. Our work develops the theory on the in-plane-sensing comb-like CMUT and is expected to be combined with the theory on the previous out-of-plane-sensing CMUT to realize 3-D-CMUT for sensing 3-D guided waves.