Authors: D. N. Shermatov | A. O. Borisov | V. A. Gafarova | I. R. Kuzeev
Source: Safety of technogenic and natural systems (article, 2026-03-04)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Local Gradient Indicator of Magnetic Variability under Cyclic Loading of Steels Introduction. Fatigue failure is one of the main causes of failure of metal structures subjected to variable loads. Initially, this damage is not visible as cracks, but it leads to the accumulation of microdefects and the redistribution of internal stresses. Currently, it is not possible to monitor the progression of these defects in large structures with a significant surface area. To detect such processes in a timely manner, highly sensitive inspection methods are required that can identify potential areas of failure with a high degree of accuracy during the early stages of structural operation. Such methods do not currently exist, and our research aims to solve this problem to a certain extent. One promising approach is the monitoring of changes in the strength of a permanent magnetic field, which reflects the evolution of material state. The current study aims to investigate the potential of spatial analysis of magnetic response to identify instability zones during fatigue loading, where the likelihood of failure is high, as well as to analyze changes in steel structure. Materials and Methods. The study focused on samples made of 09G2S steel, subjected to loading to fracture on a servohydraulic testing machine INSTRON-8801. Magnetic measurements were taken at 12 points along the sample using an IKN-2M-8 instrument. Changes in the resulting strength of the permanent magnetic field were recorded at different stages of fatigue loading. All measurements were repeated at least three times to ensure the reliability of the results. Results. It has been found, that at the stage of relative operating time Ni/Np = 0.4–0.5, anomalous changes in the magnetic field strength corresponding to the fracture nucleus were recorded at certain points. Additionally, a characteristic area of signal stabilization was observed in the range Ni/Np = 0.8–0.9. This could be explained by the temporary relaxation of stresses prior to destruction. The obtained data demonstrate the local variability of the magnetic response and confirm the sensitivity of this method to the early stages of material degradation. Discussion. The conducted research has shown that spatial analysis of changes in the strength of a permanent magnetic field can be used to locate fracture nuclei in ferromagnetic steels. This dataset can be used as a basis for training samples for intelligent monitoring systems, including neural network algorithms that focus on predicting the remaining life and automatically assessing the technical condition of structures. This is particularly important for welded structures with a high number of welds. Conclusion. The introduction of energy into a system inevitably leads to a reorganization of the structure of the material in order to adapt to external forces. This reorganization is accompanied by a change in the material's magnetic field. By recording these changes, it is possible to interpret the measurement results in terms of possible destruction, as the most efficient way for the system to utilize the supplied energy is through the formation of new surfaces, or cracks. Reliability (semiconductor) ; Fracture (geology) ; Magnetic field ; Instability ; Fatigue testing ; Fatigue limit ; Structural material Magnetic Properties and Applications ; Electromagnetic Effects on Materials ; Non-Destructive Testing Techniques