Magnetic Evaluation on Disassembly Damage of an Interference Fit Joint

Abstract

Developing a method for disassembly damage evaluation is of great significance for the key components in maintenance and remanufacturing. Disassembly of the interference fit joint between the shaft and impeller, which could inevitably bring damages to the parts’ surface, was investigated. The ferromagnetic materials FV520B (impeller) and 40CrNiMo7 (shaft) were used in the disassembly experiments. Experiments showed that different damage degrees appeared on the disassembled interface as a result of single sliding friction under different loads. The stress concentration and plastic deformation stimulated changes in magnetic domains, which led to the distortion of surface spontaneous magnetic field and the induction of metal magnetic memory (MMM) signals. The tangential components of MMM signals had peak-trough features with zero-crossing points, and the normal components showed peak features. The visible features of the distorted MMM signals could locate the position of the defects. The average damage depth Sa, peak-trough difference Wpp and peak area S had been proposed as characteristic values. The linear relationship between Sa and Wpp, Sa and S was further obtained, respectively. It indicated that the MMM technique was capable of quantitatively evaluating the disassembly damage of ferromagnetic parts, which also provided a reference for the remanufacturability assessment and the selection of repairing processes in remanufacturing engineering.