The influence of the thickness of non-piezoelectric pieces on pre-stressed piezotransducers

Analysis and Validation of Ultrasonic Probes in Liquid Level Monitoring Systems

Selecting and designing the optimum ultrasonic probe is vital for ultrasonic measurements and experiments. The amplitude of the emitted ultrasonic wave excitation signal as well as the diameter and the natural frequency of the probe seriously affect the validity of the probe results. In this paper, we analyze the significance of the key parameters of the ultrasonic probe theoretically. Further, an external fixed-point liquid level monitoring system was assembled according to the principle of ultrasonic reflection and transmission. On this experimental platform, we study the key parameters of the ultrasonic probe that affect the system evaluation through a simulation and experiment, and select the optimal sensor parameters for this experiment. The evaluations show that under the experimental conditions where the tested container is made of aluminum alloy and its wall thickness is 3 mm, the best results are obtained when the diameter of the ultrasonic sensor is 15 mm, the amplitude of the emitted excitation signal is ±15 V, and the frequency is 1 MHz. The results’ average deviation is less than ±0.22 V. The evaluations are consistent with the simulation results. This research can effectively monitor the liquid in the closed, ultra-thin-walled container, and can realize non-contact measurement. It provides an effective basis for the parameters selection and design of the ultrasonic probe in the ultrasonic-based experiments and tests.

Analysis and experimental validation of longitudinally composite ultrasonic transducers

The longitudinally cascaded piezoelectric ultrasonic transducer is studied which is composed of two longitudinally sandwiched piezoelectric transducers connected together mechanically in series and electrically in parallel. When the losses and load are taken into account, the electromechanical equivalent circuit of the transducer is obtained; the input electric impedance is analyzed and the resonance/anti-resonance frequency equations are obtained assuming one dimensional longitudinal vibrational theory. The relationship among the resonance/anti-resonance frequency, the effective electromechanical coupling coefficient, the mechanical quality factor and the electro-acoustic efficiency with the geometrical dimension, the losses, and the load is analyzed. Two longitudinally composite transducers are designed, made, and measured. It is shown that the theoretical resonance/anti-resonance frequencies, the effective electromechanical coupling coefficient, and the mechanical quality factor are in good agreement with the experimental results. It is expected that this kind of composite transducer can be used in large power and high intensity ultrasonic applications, such as ultrasonic liquid processing, ultrasonic metal machining, and ultrasonic welding and soldering.

Radial vibration and ultrasonic field of a long tubular ultrasonic radiator

The radial vibration of a metal long circular tube is studied analytically and its electro-mechanical equivalent circuit is obtained. Based on the equivalent circuit, the radial resonance frequency equation is derived. The theoretical relationship between the radial resonance frequency and the geometrical dimensions is studied. Finite element method is used to simulate the radial vibration and the radiated ultrasonic field and the results are compared with those from the analytical method. It is concluded that the radial resonance frequency for a solid metal rod is larger than that for a metal tube with the same outer radius. The radial resonance frequencies from the analytical method are in good agreement with those from the numerical method. Based on the acoustic field analysis, it is concluded that the long metal tube with small wall thickness is superior to that with large wall thickness in producing radial vibration and ultrasonic radiation. Therefore, it is expected to be used as an effective radial ultrasonic radiator in ultrasonic sewage treatment, ultrasonic antiscale and descaling and other ultrasonic liquid handling applications.