PSI - Issue 40

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Prokopyev L.A. at al. / Structural Integrity Procedia 00 (2022) 000 – 000

366 * Corresponding author. Tel.: +79681548286. E-mail address: l.prokopyev@yandex.ru 1. Introduction

L.A. Prokopyev et al. / Procedia Structural Integrity 40 (2022) 365–371

AE-control is one of the practical and promising methods of non-destructive testing. One of the advantages, according to Danegan et al. (1968) of this method is the ability to detect microdamage at an early stage of crack formation. Also, according to Builo (2017), there is a correlation between the parameters of the AE signals and the parameters of fracture mechanics. This correlation, as noted Andreev (2019), Bolshakov (2019), Prokopyev (2019) and Matvienko (2011) can make it possible to predict the behavior of cracks and minimize the risks of significant hazards or economic loss. The main disadvantages of AE-control are complexity, significant time, and economic costs of typical loading of the constructions. Also, typical loading, as a rule, emits significant noise, which significantly degrades the signal quality. Nomenclature Young's modulus position of ∆ ( ) the temperature field along the y-axis the half crack length the coefficient depending on the loading scheme the coordinate of the edge of the working area TP1 – TP4 thermocouples AE1 – AE4 acoustic emission sensors , constants, obtained from experimental data x, y This article offered to study and develop the method of local low-temperature thermal loading for AE-control, developed by Andreev and Bolshakov (2016, 2017) in the industry to detect defects and predict defect behavior. The advantage of this loading method for acoustic emission testing is simplicity, low time, and economic costs. The low noise level of this loading method increases the reliability and efficiency of AE-testing and makes it possible to predict defect behaviour by fracture mechanics methods, studied by Parton and Morozov (1974). Therefore, it is necessary to study the possibility of using local low-temperature thermal loading for AE control to predict the behavior of cracks. Therefore, it is necessary to solve the following tasks: develop the scheme of low-temperature thermal loading of a steel flat plate specimen with a crack; calculation of the stress-strain state and stress intensity factors at the crack tip under local low-temperature thermal loading; determination of the relationship of the acoustic emissions total count with the stress intensity factor. 2. The stress intensity factor in a gradient temperature field Flat plate specimen of “St.3” steel with 3mm thickness selected for experiment scheme. This scheme is designed for uniaxial loading of the central region of the plate with a distributed tensile load with negligible stresses along the "x" axis. Two holes are made to compensate for deformations in the x-axis direction. In the plate's remote region, which is not subject to low-temperature influences, there is a displacement due to the rigidity of the plate. The coordinate axis tensile stresses Na time stress intensity factor (SIF) acoustic emission total count t