This paper presents a design optimization of a membrane-based ultrasonic piezoelectric transducer using micromachining by finite element simulation. The transducer can be used to generate ultrasound using the piezoelectric film to excite the vibration of the transducer membrane. The objective is to maximize the vibration magnitude of the membrane by optimizing the structure of the transducer, when the exciting signal is fixed. The size and the shape of the piezoelectric film were selected as the design parameters to optimize the structure of the transducer. Based on the theoretical analysis, it is found that the absolute values of the stresses in the center and the boundary of the diaphragm are greater than that on the other regions of the film, with the directions of the stress on center and boundary opposite to each other. In order to achieve the maximum exciting efficiency, the discrepancy in the stresses between the center and the boundary on the diaphragm should be maximized. In this paper, totally four different piezoelectric film structures are analyzed for optimizing the exciting efficiency of the transducer. The finite element models of the transducer were created using ANSYS. The simulations based on the three design options were performed; and through the comparison of the simulation results, the optimal structural parameters of the piezoelectric film are identified. Finally, the direction of the design improvement for the exciting efficiency of the transducer is provided.

Based on a guided wave technique and a dispersive waveform prediction method, this paper presents a method which can be used to image defects in pipes. According to this method, a non-axis symmetrical end loading transducer can be used to excite an L (0, 2) mode and receive its echo at one end of the pipe. By rotating the said transducer with a specific space in the circumferential direction of said end and then operating the said transducer, twenty-four received signals can be obtained so as to image and locate those defects. Finally, we concluded that it is effective to image and recognize defects in two kinds of pipes including a one-holed pipe and a two-partially-circumferential-notched pipe using the presented method.