Analysis of magnetic changes induced by temperature disturbances in the goaf

In view of the influence of temperature field changes in the goaf on the performance of magnetic materials, this paper combines experiment and numerical simulation to explore and analyze the law of temperature propagation in the goaf and the mechanism of abnormal magnetic induction intensity in NdFeB rubber magnetic lines under the influence of a coupled temperature field. The results indicate that the measuring point temperature follows a quadratic function variation with the temperature measurement distance, and when the measurement distance exceeds 0.75m, the measuring point temperature reaches equilibrium with the ambient temperature. The temperature variation obtained from numerical simulations aligns with the experimental measurements, revealing three distinct temperature variation zones: a rapid temperature drop zone, a slow transition zone, and a stable approaching zone. As the temperature measurement distance increases, the curvature of the isothermal lines on the measuring plane gradually decreases and tends to become parallel, while the spatial isothermal surfaces transition from curved to flattened. With increasing temperature, the antagonistic effect between thermal excitation and magnetic exchange interaction strengthens, gradually becoming dominant, leading to disorderly arrangement of magnetic moments and a reduction in magnetic induction intensity. Additionally, as the temperature rises, the thermal expansion effect of the rubber matrix enhances the encapsulation of magnetic powder particles, suppressing the magnetic dipole interaction, resulting in a “two-point, three-zone” variation pattern of magnetic induction intensity, characterized by low-temperature, medium-temperature, and high-temperature zones. Among them, the magnetic induction intensity decreases most rapidly in the medium-temperature zone.