Электромагнитно-акустический толщиномер для контроля металлоизделий с диэлектрическими покрытиями

Abstract

Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.11.13 – Devices and methods of testing and materials structure determination. – National technical university "Kharkiv Politechnical Institute", Kharkiv, 2015. Thesis is devoted to solution of important theoretical and practical task to ensure ultrasound control of the metal products thickness by using electromagnetic-acoustical method in cases of dielectric coatings (gaps) with thickness up to 10 mm. Work includes analysis of existing acoustic methods and devices for thickness measurement, their main advantages and disadvantages are reviewed. Based on the results of analysis of the given disadvantages, the most advanced ways was set off - electromagnetic-acoustical (EMA) method. The problems of selection of the optimal signal agitate sonorous vibrations by EMA method were reviewed. Calculations of the taken energy are given for the analysis of the practicability to use variants of probing signal. Electric model of amplifier output stage of probing signal and sensor is reviewed, peculiarities of its operation are described. Results of researches and developments dedicated to increase thickness measurement quality and efficiency are given. Matters to build of the transmitting and receiving analog tracts are reviewed. The signal level dependence on voltage research on sensor's transmitting winding are conducted. Impact of a gap on the signal level was examined. Results of the dependence of dead spot length on a gap and methods to its reduction are given. Factors affecting accuracy of control are determined. EMA thickness gauge was designed. The main factors of design are examined. The digital processing algorithm of the received data was reviewed. Metrological characteristics of the developed device were made.