Practical results and prospects of using fiber optical sensors of acoustic emission for diagnosting the technical condition of aircraft units

Abstract

Peripheral sensors for measuring aircraft parameters are an integral part of any system for diagnostics and forecasting of technical condition. Their principle of operation in relation to operation at aviation complexes is to convert mechanical, electromagnetic or light quantities into electrical ones for their subsequent processing. The process of radiation of disturbances propagating in the material caused by the dynamic local rearrangement of the structure of materials under the action of internal stresses leading to a change in the crystal lattice or the movement of micro- and / or macrodefects is called acoustic emission. So, the analysis of differences in the form of acoustic waves allows the classification of the type of deformation: crack or plastic deformation, which allows you to more accurately determine the current state of the airframe or diagnosed nodes. The principle of operation of such sensors is based on the effect of converting the linear dimensions of a Bragg cell, made on an optical fiber, into a change in the reflected wavelength. A necessary condition for obtaining correct results of measurements of stress states is the need for temperature compensation of the Bragg cells, which is achieved by introducing additional cells that are mechanically decoupled from the material being diagnosed and react only to the temperature component. The advantage of this method is the absence of the need for additional adjustment of the cells and their alignment, as well as the independence of measurements from the effects of electromagnetic radiation; the sensors are lightweight, vibration-resistant, and insensitive to electromagnetic fields. The article presents the practical results of using fiber-optic acoustic emission sensors for diagnosing the technical condition of critical components and assemblies of aircraft, as well as outlines the prospects for their deepest integration into a unified information and analytical system for diagnosing and predicting the technical state of aviation complexes. The developed technical solutions aimed at simplifying the methods of processing broadband acoustic emission signals, which make it possible to design acoustic emission sensors based on optical fiber, are structurally simpler and cheaper, with an increased signal-to-noise ratio, due to one conversion of an acoustic-optical signal into an electrical one.