Analiza współoddziaływania fali mechanicznej silnej nieciągłości z czujnikiem piezoelektrycznym (The analysis of interaction of a strong discontinuity wave with piezoelectric sensor)

Radziszewski, Leszek (2015) Analiza współoddziaływania fali mechanicznej silnej nieciągłości z czujnikiem piezoelektrycznym (The analysis of interaction of a strong discontinuity wave with piezoelectric sensor). Monografie, Studia, Rozprawy (M65). Wydawnictwo Politechniki Świętokrzyskiej, Kielce. ISBN 9788363792220

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In this work the influence of the surface loading by piezoelectric contact sensor by measurements of transient disturbances in solids on testing results was investigated analytically and experimentally. In chapter 2 the one-dimensional model of the mechanical contact between the ultrasonic sensor and the solid medium was developed. Contrary to the previous papers the transducer was assumed not to be a rigid mass of known mechanical impedance but a continuous mass in a form of a rod. In this rod will propagate in the longitudinal direction disturbances with the velocity of a longitudinal wave and with a plain wave’s surface. An axial local impact causes the propagation of a strong discontinuity waves in a rod. We would analyze the propagation of the transient distortion locally, e.g. at the front. The influence of the sensor load on the displacement field generated by transient disturbances in the measured solids was investigated analytically. The displacement field was calculated with the d’Alambert’s method. Also, the analysis of electrical transients generated by piezoelectric contact transducer is given. The analysis of interaction a strong discontinuity wave with a fragmental-continuous model of transducer on the interface between sensor and investigated material was developed. The influence of viscoelastic parameters of a medium on the propagation of a front face of a strong discontinuity wave was analyzed, as well. The three-parameter model e.g. standard model, as a model of a body with viscoelastic properties was taken. Different methods of generation in a solid media a strong discontinuity wave were presented and compared in chapter 3. The comprehensive review of literature on laser ultrasound generation in metals and polymers has been done. Particular attention was paid to mathematical description of generation by laser ultrasonic volume waves. In chapter 4 an experimental investigation were presented. The non-contact ultrasonic technique of wave generation was used to test polymers and polymers composites. Transients elastic waves were generated with a Q-switched Nd:YAG laser. Measurements aiming at the determination of the macroscopic parameters of propagation of bulk waves (directivity patterns, amplitude, velocity and frequency distribution) were made in unidirectional glass/epoxy and isotropic polyvinyl chloride plastic thick plate. The influence of a constrained surface on the ultrasound parameters is discussed. The variations of the macroscopic parameters of propagation as functions of distance from the epicenter were studied. PZT-ceramic standard ultrasound probes were used as receiver. In chapter 5 the most important conclusions are presented. Finally, in appendix 1 and 2 a detailed description of calculation presented in chapter 2 were given.

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