Research of the features of location of acoustic emission signals in complex composite structures

Аuthors

Yakovlev D. S.¹, Khizhnyak S. A.², Zotov A. A.²

1. Branch of PJSC «UAC» — OTA, Moscow, Russia
2. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

Abstract

The article presents the results of an experimental study on the features of propagation and location of acoustic emission (AE) signals in composite materials (CM). The relevance of the work is determined by the complexity of location determination under impact loading as applied to aviation composite structures. These structures represent objects of complex geometry, which affects the reliability of technical condition diagnostics of the object under study.

The aim of the research is to develop a methodology for locating AE signal sources on an object, taking into account the influence of the geometric features of the test object (TO) and the material structure on the measurement results. Evaluation of the error in coordinate determination under various sensor placement schemes.

The complex multilayer and anisotropic structure of CM makes them vulnerable to specific damage types: delaminations, fiber breaks, and matrix cracking. The occurrence and accumulation of such defects significantly affects the structure’s residual life, strength, and load-bearing capacity. Timely detection of internal damage substantially increases operational safety and reduces the risk of destruction during operation.

The method of locating AE signals using built-in monitoring systems is one of the most promising, and at the same time, one of the most complex in terms of software implementation, for monitoring the re-liability of aviation structures.

The practical application of AE monitoring techniques for aviation structures is associated with a number of fundamental difficulties, such as:

• ambiguity in the interpretation of multiple reflections, especially in enclosed spaces and complex geo-metric configurations;

• the influence of temperature gradients and other operational factors on wave propagation velocity;

• distortion of wave fronts due to structural inhomogeneities, leading to errors in the calculation of signal arrival times.

Such problems, combined with a relative shortage of data on the behavior of AE signals on full-scale objects (due to the predominance of laboratory studies on model specimens that do not account for the operational features of structures), lead to difficulties in applying the control method to real objects.

Registration of AE monitoring results was carried out, including AE signal arrival times, their amplitude and frequency composition, along with analysis of the influence of structural inhomogeneities.

Keywords:

acoustic emission, source location, field experiment, fiber optic sensors, Bragg grating

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