No 11 (2023)

The studies were carried out in a test facility based on the original biaxial testing machine created at the IES UB RAS, designed to determine the physical properties of materials during elastic-plastic deformation independently along two axes. Finite element modeling of the stress-strain state of a cruciform nickel specimen has shown that, under symmetric biaxial tension, equivalent von Mises stresses are uniformly distributed in the central part. The results of microstructural studies indicate that dynamic recrystallization takes place in the material during biaxial deformation at room temperature. The results of studying the behavior of the hysteretic magnetic characteristics, magnetostriction, Barkhausen magnetic noise parameters, and electromagnetic parameters of nickel under biaxial symmetrical tension have been presented. A unique relationship between the coercive force and equivalent stresses in the region of plastic deformation has been revealed. It has been shown that such magnetic parameters as maximum magnetic permeability and the maximum in the field dependence of differential magnetic permeability, as well as the amplitude and frequency of the eddy current signal determined at a frequency of 10 kHz, vary monotonically with increasing equivalent stresses under both elastic and plastic deformations.

Cracks indicates the real time deformity in concrete structures. It is characterized as discontinuity in terms of shape and size of the concrete structures. To ensure the structural health and safety, crack detection is an important task. The traditional methods of crack detection include visual introspection, ultrasonic and hand-held testing of crack. These methods require a high human intervention along with an experienced and skilled inspector. Moreover, these methods are subjective and time-consuming process which fails to identify the crack of the complex concrete structures properly. To overcome these issues, a grab-cut with improved Sobel has been proposed for automatic crack detection from the concrete structures. The proposed method works as a two-step model where cracks regions are segmented in the first step and a precise crack assessment is performed in the second step. Furthermore, to improve the efficacy of Sobel, the mask is modified with the aid of local variance of the image instead of using conventional mask of the filter. For the experimentation study, the images of self-prepared concrete sample have been acquired. The effectiveness of the proposed method has been compared with respect to various pre-existing methods like Sobel, Prewitt, Robert, LoG, Zero Cross and Canny. The comparative qualitative result exhibits that the proposed method surpasses the outcomes of the other pre-existing methods. Additionally, for easy implementation and application point of view a web tool of the proposed method has been developed. The web tool can be utilised by the civil infrastructure maintenance agency and construction engineers in the task of structure maintenance.

The article considers nondestructive testing of soldered lap joints of electric machines by means of a two-element eddy current tangential probe, excitation and measuring windings of which are placed on both sides of the test object. To ensure shielding from closely located current-conducting elements two active shielding windings are used. Using the tangential probe and reference blocks, replicating the shape and dimensions of the tested joint and imitating 0% and 100% soldering, allows measurement of soldering of busbar lap joints.

In earlier work the possibility of diagnosing a defect of a steel wire rope by spectral composition of its free transverse vibrations was substantiated. In the present work, an analytical model of transverse vibrations of a steel wire rope with local damage is proposed. The presence of the defect in the model is taken into account only in the form of a loss of bending stiffness of the corresponding section without changing the specific mass along the length. The model represents three homogeneous rope sections “stitched” together, where the middle one represents a defective section with a lower value of bending stiffness. According to the model calculations, it is shown that the character of the dependence of the natural frequencies of oscillations on their number practically does not change in the presence of a defect. However, its presence and location affects the ratio of vibration amplitudes of undamaged sections, which can be used to monitor the condition of the rope.