Studying the frequency spectrum of acoustic emission signals by the infradyne transform method

Abstract

Background. The process of formation and development of microcracks in the walls of a tank with liquefied hydrocarbons can inevitably lead to a breach of tightness and, as a consequence, to the creation of a fire-hazardous situation and, yes, an explosion of the tank. The acoustic emission method allows to diagnose the tightness of the walls of the reservoirs, as well as machine parts and structures, in the mode of their operation. The purpose of the work was to develop a technique for reducing the influence of lowfrequency signals of external noise on the spectrum of recorded acoustic pulses and determining the type of microdefect corresponding to this frequency spectrum. Materials and methods. To reduce the influence of low-frequency signals of external noise on the spectrum of recorded acoustic pulses, an original technique is proposed based on the infradine RF conversion of acoustic emission signals, followed by the transfer of the frequency spectrum of the received acoustic emission signals from the low-frequency ultrasound frequency range to three separate high-frequency spectral regions without changing parameters of the frequency spectrum of acoustic signals. Results. A functional block diagram of an acoustic installation has been developed that allows recording acoustic emission signals with subsequent infradine RF conversion and separation into three separate frequency channels, simultaneously registering the number of pulses and the amplitude of individual acoustic emission pulses. The parameters of LC circuits of bandpass filters of resonant RF amplifiers have been calculated. Conclusions. The use of the method of infradine conversion of acoustic emission signals arising in the elastic deformation mode allowed to significantly reduce the influence of low-frequency external noise signals on the spectrum of recorded acoustic pulses, increase the sensitivity of the acoustic installation and determine the type of micro-defect formed in various machine parts and structures in their operation mode.

Keywords

• spectrum
• acoustic emission
• structures
• transformation
• frequency
• sensor
• resonant amplifier
• pulse counter