Defektoskopiâ

In this paper we propose to automate the classification of reflector types by TOFD-echoes using ResNet-18 convolutional neural network. The main focus is on modeling and classification of reflectors such as cracks, pores, non-welds and void areas. Experiments included training the model on TOFD echoes calculated both in a numerical experiment and TOFD echoes measured during ultrasonic inspection. The results showed high classification accuracy: 96.2 % in the numerical experiment, 97 % on experimentally measured TOFD-echoes with different types of reflectors. The study confirmed the possibility of using neural networks to determine the reflector type from TOFD-echo signals, which allows to automate the process of nondestructive testing and reduce the influence of human factor. For further development of the method it is suggested to use segmentation models for processing images with several reflectors

The article discusses the possibility of using the acoustic-electrical transformation method to detect cracks and mechanical compressive strength of concrete. Numerical and experimental studies of changes in the parameters of the electromagnetic response of model samples of concrete made of a cement-sand mixture with a crack to a deterministic pulsed acoustic impact are presented. It is shown that the presence of a crack is determined by changes in the amplitude-frequency parameters of the electromagnetic response from the sample. An example of determining the locations of weakening of the mechanical strength of a concrete construction beam based on the parameters of electromagnetic signals is given. The results of comparative tests for determining the mechanical compressive strength of concrete, obtained using a calibrated sclerometer and an acoustoelectric method, are shown. The results of monitoring the mechanical strength of concrete structures of an operating bridge crossing over a river are also presented based on the parameters of the electromagnetic response that arise during impact probing with acoustic pulses

The effect of annealing temperature of nickel plastically deformed according to various schemes on the change on its microstructure and level of magnetic characteristics was investigated. The processes of recovery and recrystallization in the nickel structure are reflected quite informatively both in the change of such magnetic characteristics as coercive force, maximum magnetic permeability and in the change of the field dependence of differential magnetic permeability. In different structural states (deformed and recrystallized structures), the position of the peak of differential magnetic permeability changes, as does its height. Thus, the established patterns can be used to analyze the processes of nickel recrystallization and assess the change in its structural state during manufacturing or operation

The concept of “thermal equivalents” of impact damage in composites, created by iteratively fitting the parameters of flat bottom hole defects, has been elaborated.  In thin-walled composites, impact damage tends to be located near the surface opposite to the impact, so thermal inspection on the rear surface of the product is most effective for their detection. Detection of defects on the front surface is associated with small signal amplitudes in the region of temperature indications and requires the use of the thermal equivalent of impact damage in the form of a combination of flat bottom hole defects.  On the rear surface, temperature indications of impact damage are often butterfly-shaped and characterized by a large area of defect “footprints”. Single flat-bottom flaws can serve as thermal equivalents of such defects. The proposed concept of thermal equivalents of real defects in composites is verified experimentally on a carbon fiber-reinforced plastic specimen with impact damage of the 62 J energy

To determine the relationship between the stress-strain state induced by bending and several magnetic parameters, a laboratory three-point bending test was performed, and measurements were made during the test without removing the load using DIUS-1.21M instrument. The load at which plastic deformation started in the specimen was determined. Graphs of dependence of coercive force, residual magnetic induction and hysteresis loop area on the applied load were plotted. It is revealed that elastic bending leads to a monotonic drop in the coercive force and hysteresis loop area and to an increase in the residual magnetic induction. Elastic-plastic deformation of the beam leads to a strong decrease in the residual magnetic induction, but for an unambiguous assessment of the stress-strain state under a load up to 20 kN, a multi-parameter magnetic testing is required