A Metal Abrasive Particle’s Classification and Identification Method Based on Dual-Frequency Asymmetric Excitation Magnetic Field

Material identification of oil abrasive particles is the key to accurate diagnosis and tracing of mechanical equipment failures. Addressing the bottleneck of existing symmetrical magnetic field excitation methods in distinguishing metal types, this article proposes a metal abrasive particle classification and identification method based on dual-frequency asymmetric magnetic field excitation. An external sensing and internal excitation nested three-coil detection structure is designed in this article. Based on the differences in frequency response characteristics of ferromagnetic and nonferromagnetic abrasives, a dual-frequency excitation strategy of 195 and 872 kHz is adopted to construct an asymmetric magnetic field spatial distribution. This method can realize the detection and material differentiation of different metal abrasives. At the same time, the influence of particle size and velocity on the sensing signal is also explored. Experimental verification demonstrates that this method can effectively distinguish the magnetic properties, size, and material of iron, 440C steel, copper, and aluminum metal abrasive particles in a 6-mm oil pipeline based on the multidimensional characteristics of the induced voltage signal, such as the number of valley peaks, amplitude difference, waveform trend, and distribution position. The theoretical minimum detectable particle sizes reach 154, 114, 140, and $215~\mu $ m. This method provides an effective technical means for online detection of the abrasive status of mechanical equipment.