X80 pipeline steel is widely used in long-distance oil and gas transportation due to its high strength and toughness. However, reducing wall thickness to cut costs can lead to stress concentration during forming and under external loads. Since stress can significantly alter the magnetic properties of ferromagnetic materials, magnetic characterization techniques provide a promising approach for stress evaluation; Nevertheless, variations in magnetic parameters caused by plastic strain introduce challenges in accurate stress assessment. In this study, we performed a series of uniaxial tension tests to introduce different levels of plastic strain and identified two hardening stages: an internal stress-dominated stage and a dislocation density-dominated stage. Corresponding models were used to describe their influence on magnetic behavior. Based on the energy minimization principle, the relationship between coercivity and stress under uniaxial loading was derived. A magneto-mechanical behavior model for the elastoplastic stage was then established by incorporating the effect of internal stress and dislocation density. The coercivity variation under combined elastic-plastic deformation was subsequently analyzed. Theoretical predictions show good agreement with experimental results, and a representative example was presented to demonstrate the model's applicability in engineering contexts.
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