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No 4 (2023)
Articles
Acoustical characteristics of solid elastic mediums with oriented microfructures
Abstract
Model for interaction of plane elastic longitudinal waves with contains oriented microfractures with specific boundary conditions for “linear slip@ approximation is developed. The form of dispersion equation is defined in approximation of Bloch and Floque waves theory. Results of its solution which define character of functions for propagation phase velocity and attenuation coefficient of effective longitudinal wave in dependence on crack faces microfracture parameters and other model parameters.
Defektoskopiâ. 2023;(4):3-13
3-13
Multiple damage prediction in tubular rectangular beam model using frequency response-based mode shape curvature with back-propagation neural network
Abstract
In the civil infrastructure, the structures made up of tubular sections played an important role due to an economic point of view, lower self-weight, and stability against functional loads. The periodical maintenance or inspection of the structure is mandatory nowadays to achieve the potential utilization of the structural system. In this study, an experimental, numerical, and analytical study is carried out to investigate the structural fault and its severity in a tubular rectangular beam made up of structural steel. Modal parameters are extracted with the help of a dynamic data logger (B&K) by exciting an impact hammer on model structure and extracting a data with a set of unidirectional accelerometers. First, two displacement mode shapes are extracted using obtained modal parameters. The modal parameters are expected to contain environmental noise during experimentation, so, de-noising is must to obtain noise-free data. Artificial neural network training is utilized to reduce the noise from experimental modal parameters. Using the modified modal parameters, the mode shape curvature is obtained, and so-called modified mode shape curvature (MMSC) is used to calculate the curvature damage index. The curvature damage index is appropriate to investigate multiple fault locations with different fault levels in tubular rectangular beam structures.
Defektoskopiâ. 2023;(4):14-36
14-36
Possibilities of manual eddy current testing for measuring the depth of contact-fatigue cracks of the surface of rolling rails
Abstract
The possibility of using the eddy current method to assess the depth of cracks in the surface of rolling rails in operation for planning the work of a rail grinding train is investigated. Experimental studies of the influence of the excitation frequency and the angle of inclination of the eddy current converter, the state of the surface, the depth and angle of inclination of the surface crack on the amplitude and phase of the eddy current signal are carried out. The possibilities of the amplitude-phase method of detuning from interfering factors associated with the slope of the transducer and the curvature of the controlled surface are determined. The resolution of the flaw detector was investigated when evaluating the characteristics of two or more closely spaced cracks - a defect of the "grid" type of cracks. The depth of surface cracks in the range from 0.1 to 1.4 mm was determined by metallographic examination after eddy current control. Optimal control parameters have been experimentally substantiated and a correlation between the crack depth and the projection of the signal amplitude in the direction perpendicular to the direction of change of the interfering factor - the angle of inclination of the transducer - has been established.
Defektoskopiâ. 2023;(4):37-45
37-45
Iterative reconstruction of images of aluminum casting taking into account prior information
Abstract
The problem of low-projection X-ray tomography is a typical representative of the class of ill-posed problems. A practical solution to this problem will expand the scope of the X-ray tomography method. The problem of low-projection X-ray tomography is often a problem with a lack of initial data and can only be solved using a priori information. To introduce the necessary additional information into the numerical algorithm, the methods of iterative reconstruction of tomographic images are the most suitable. One of the approaches for introducing this kind of information is described in this article.
Defektoskopiâ. 2023;(4):46-55
46-55
Non-destructive testing of an aluminum alloy welded joint based on a mathematical model of the thermal welding process and computer microtomography
Abstract
Strength control of welded joints is used in many industries. X-ray microtomography as a method of non-destructive testing allows not only to detect the presence of defects, but also to classify them and assess the size of cracks and non-crack-like defects (pores). This article discusses the non-destructive testing of welded joints of aluminum alloy 6061 T6 using computer micrototomography and a mathematical model of the thermal welding process implemented in ANSYS Workbench. Experimental results of the X-ray microtomograph are presented, and the size of defects in this sample is estimated. The mathematical model allowed us to obtain the thermal histories at which the faults were formed.
Defektoskopiâ. 2023;(4):56-65
56-65
IR thermographic analysis of aperiodic energy entities in the atmosphere (tomsk phenomenon 17 years later)
Abstract
This study continues the investigation of 2006 intended for the analysis of aperiodic energy phenomena in the atmosphere by using the technique of infrared thermography. It is experimentally confirmed the existence of atmospheric energy entities of unknown nature in the zones subjected to prolong energy exposure. A spatial/temporal mathematical model of this phenomenon is proposed to match well the observed experimental data.
Defektoskopiâ. 2023;(4):66-69
66-69