PSI - Issue 82

Valentyn Uchanin et al. / Procedia Structural Integrity 82 (2026) 288–294 Valentyn Uchanin et al. / Structural Integrity Procedia 00 (2026) 000–000

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Fig. 2. (a) Design of the attachable-type magnetic transducer with a generalized scheme of the magnetic analyzer: 1 – U-shaped core; 2 – magnetization windings; 3 – Hall sensor for measuring magnetic flux in the magnetic circuit; 4 – test object; 5 – control, measurement, and indication unit; 6 – current supply unit for the magnetization windings; 7 – magnetic flux measurement unit, and (b) the KRM-C-MA magnetic analyzer with an attachable-type magnetic transducer mounted on the tested specimen.

Fig. 3. (a) Correlation between the coercive force H c and hydrogen concentration C H in the metal, and (b) between the residual induction Br and hydrogen concentration C H .

2.2. Determination of mechanical stresses in ferromagnetic steel structures by the eddy current method based on magnetic anisotropy evaluation The stress state in MPs concerned with the internal forces and deformations caused by various factors, including internal pressure, temperature variations, or external loads, is a critical factor for their safe and reliable operation (Osadchuk et al., 2006; Xue et al., 2025). Even in the absence of external load, the transported liquid or gas exerts pressure on the walls of the pipeline, creating circumferential and longitudinal stresses. External forces like soil pressure or ground movement can create bending and axial stresses. Circumferential stress acts circumferentially around the pipe and is primarily caused by internal pressure. Longitudinal stress acts along the length of the pipe and is influenced by internal pressure, axial loads, and temperature changes. Bending stress arises from bending moments applied to the MP, often due to external loads or uneven support. Shear stress acts parallel to the surface of the pipe and is associated with torsion or bending. As mentioned above, inspection of MPs is complicated by their location in the soil. Therefore, the assessment of the distribution of abnormal stresses in the pipeline is carried out at open sections of crossings with highways, or it is necessary to use earthworks by excavating the pipe in critical areas. Therefore, the development of the NDT method for in-service MP stress evaluation provides critical support for structural integrity and safe monitoring. The known NDT techniques for MP stress monitoring are primarily based on ultrasonic, X-ray, or neutron diffraction methods, as reported by Gou et al. (2011), Li et al. (2025), Osadchuk et al. (2006), and Wimpory et al. (2009). Additionally, various electromagnetic NDT techniques can be employed for stress evaluation in MP, as reported by Abuku (1977), Garikepati et al. (1988), Langman and Mutton (1993), Lindgren and Lepistö (2002), Nutor et al. (2017), Uchanin et al. (2018), Uchanin and Ostash (2019), and Vourna et al. (2018). The eddy current method based on MA evaluation can be used to measure stresses in MPs made of FSS (Uchanin et al., 2018). The developed methodology was used to monitor an underground ammonia pipeline (355 mm in diameter, and a wall thickness of 8 mm) under long-term operating conditions with pressure up to 90 atm. Pipeline