Определение координат отражателей в плоскости, перпендикулярной сварному соединению по эхосигналам, измеренным преобразователями по схеме TOFD

The TOFD method, which is widely used in ultrasonic flaw detection, makes it possible to distinguish a crack from a volume reflector by the phase of the echo signals and to determine its height with high accuracy. However, the TOFD method without scanning the piezoelectric transducers across the weld joint does not allow to determine the displacement of the reflector from the center of the welded joint, which is very important when evaluating the results of the control. The scanning devices used for this purpose have a complex design, their price is higher than that of one-dimensional scanning devices, and, most importantly, the control time increases significantly. If the echo signals reflected from the bottom of the object of control are used, taking into account the change in the wave type, then a combined image of the reflector can be obtained from a set of partial images recovered by the digital focusing antenna (DFA) method. If we use the echo signals measured in the combined mode for each piezoelectric converter, we can estimate the displacement of the reflector across the welded joint with an accuracy of ±1.5 mm. Numerical and model experiments have confirmed the efficiency of the proposed approach.

Comparison Between a Wideband Fractal-Inspired and a Traditional Multicantilever Piezoelectric Energy Converter

Harvesting energy from ambient vibrations in order to power autonomous sensors is a challenging issue. The aim of this work is to compare the power output from an innovative wideband fractal-inspired piezoelectric converter to that from a traditional multicantilever piezoelectric energy converter. In a given frequency range, the converters are tuned on the same eigenfrequencies. The effect of the input acceleration and of the resistive load applied to the converters is investigated experimentally for each of the three eigenfrequencies in the range between 0 and 120 Hz. The fractal-inspired converter exhibits a significantly higher specific output power at the first and third of the eigenfrequencies investigated.

Experimental Comparison Between a Fractal-Inspired Multi-Frequency Piezoelectric Energy Converter and a Traditional Converter

Harvesting energy from ambient vibrations in order to power autonomous sensors is a challenging issue. The aim of this work is to compare the power output from an innovative multi-frequency fractal-inspired piezoelectric converter to that from a traditional multi-cantilever piezoelectric converter. The converters are designed in order to give the same eigenfrequencies in a given range and a prototype of both is built using commercial materials. The experimental tests investigate both the effect of the acceleration and of the resistive load applied to the converters for each of the three eigenfrequencies in the range between 0 and 120 Hz. The fractal-inspired converter exhibits a significantly higher specific output power at the first and third of the eigenfrequencies investigated.

A Fractal-Inspired Multi-Frequency Piezoelectric Energy Converter: Design and Experimental Characterization

A promising harvesting technique, in terms of simplicity and efficiency, is the conversion of ambient kinetic energy through piezoelectric materials. This work aims to design and investigate a piezoelectric converter conform to a fractal-inspired, multi-frequency structure previously presented by the author. A physical prototype of the converter is built and experimentally examined, up to 120 Hz, in terms of modal response and power output. Three eigenfrequencies are registered and the power output is particularly good at the fundamental eigenfrequency. Also the effect of the resistive load applied to the converter is investigated.