Abstract:The integrity of cathode carbon block in aluminum electrolysis cell is crucial to the life of the cell, and it is prone to cracks and damages under the action of high temperature, electrolyte erosion and other factors, and it is difficult for traditional inspection techniques to capture the early characteristics of cathode carbon block damages and the dynamic change process. In view of this, the acoustic emission detection technology was introduced to detect the acoustic emission signals generated in the process of carbon block breakage, and uniaxial loading tests were carried out on graphite and graphitized cathode carbon blocks. The stress thresholds for crack closure stress σ_cc, crack initiation stress σ_ci, damage stress σ_cd and peak stress σ_cp were determined by cumulative AE ringing counts and axial stiffness analysis. Based on these stress thresholds, the damage process of cathode carbon block is divided into four stages, including the compaction stage, elasticity stage, stable crack growth stage and unstable crack growth stage. Meanwhile, the acoustic emission parameter signal characteristics of each stage were systematically investigated to reveal the acoustic emission response laws of different breakage stages. The study shows that: 1) The acoustic emission b value of the cathode carbon block is at a low level with small fluctuation for a long time in the stable crack growth stage and unstable crack growth stage, which indicates that the crack development rate of the carbon block is relatively smooth during the destabilized breakage process. 2) The acoustic emission S value of the graphitized cathode carbon block is lower than that of the graphite cathode carbon block in the process of the damage of the carbon block, which indicates that the expansion rate of the cracks within the graphite cathode carbon block is more drastic. When the S value is in the middle-high level for a long time, it indicates that cathode carbon block breakage may occur. 3) The results of tension-shear crack percentage for each stress stage based on RA-AF statistics show that the increase in shear crack percentage is a precursor feature of cathode carbon block approaching breakage.