Formation of Probing Signals of Piezoelectric Transducers for Ultrasonic Testing

Abstract

Introduction. Reducing the duration of the probing pulse at the output of a multilayer radiator is an urgent task of acoustic non-destructive testing. This not only improves the resolution of the system and the accuracy of determining the coordinates of defects, but also reduces the length of the dead zone. The most versatile method for achieving short signal duration is mechanical damping. The use of RL circuits connected to the electrical side of a piezoelectric transducer (PET) for this purpose has been studied to a lesser extent. Of interest is a comparative study of the potential possibilities of the two indicated methods for obtaining a short signal.Aim. To carry out a comparative study of two options for reducing the duration of the probing signal in order to establish their preferential use in the practice of ultrasonic testing.Materials and methods. To determine the boundaries of the preferred application of one of the methods in comparison with the other, a mathematical apparatus is used based on the use of integral calculus, as well as numerical calculation methods. When constructing a mathematical model of piezoelectric transducers operating in a pulsed mode, the method of analog circuits is used in combination with the spectral method based on Fourier transforms. Numerical calculations were performed in the MathCad environment.Results. It was established that the use of an electrical corrective circuit with optimal parameters makes it possible, across a wide range of changes in the values of the specific acoustic resistance of the protector, to achieve a shorter duration of probing signals at the output of the probe than in the case of using a damped probe with values of the specific acoustic resistance of the damper zд latitude 10⋅106 Pa⋅s/m. At zд >10⋅106 Pa⋅s/m, preference should be given to mechanical damping of the piezoelectric element. It was found that the amplitude of the signals at the output of the PET with a corrective circuit connected thereto exceeds the amplitude of the signal when the piezoelectric element is damped.Conclusion. The results obtained allow an a-priori evaluation and comparison of PET capabilities using two methods for creating a short probing signal, as well as a justified selection of materials for creating a protector across a wide range of specific acoustic resistances. The correctly selected parameters of the structural elements of the probe makes it possible to improve the resolution of radiation-reception systems, reduce the length of the dead zone, and increase the accuracy of determining the coordinates of defects. This ultimately improves the quality of acoustic testing of materials and products.