Wear and abnormal fracture failure mechanisms of alloy teeth in TBM insert tooth disc cutters

Insert tooth disc cutters are among the commonly used cutters in TBMs (Tunnel Boring Machines). However, due to the sharpness, protrusion, and small contact area between the alloy teeth and rock, these cutters are prone to uneven loading and stress concentration. This makes the alloy teeth susceptible to abnormal failure modes such as chipping, breakage, and detachment during operation. To improve the compatibility of insert tooth disc cutters with rock, this study investigates the wear and failure mechanisms of these cutters. In an analysis of failed disc cutters, it was found that 53% of the alloy teeth had failed, with breakage and chipping accounting for the highest proportions, at 37% and 15%, respectively. The study proceeded by characterizing the microscopic wear morphology of both the cutter ring matrix and the alloy teeth. The results revealed that the wear of alloy teeth is characterized by shallow surface scratches and pits caused by abrasive, adhesive, and fatigue wear. In contrast, the matrix of the cutter ring exhibited plowing grooves formed primarily by abrasive and adhesive wear. Furthermore, a finite element model (FEM) of the rock-breaking process was established and validated against experimental data to analyze the stress distribution and surface contact pressure of the alloy teeth during rock cutting. Simulation results indicated significant impact phenomena as the alloy teeth penetrate the rock, which reduces their service life. Both spherical and wedge-shaped teeth exhibited noticeable stress concentration and uneven loading, with the regions of stress concentration closely aligning with the areas where chipping occurred. This correlation confirms that the primary causes of tooth chipping are stress concentration and uneven loading. This research provides valuable insights for the selection and optimized design of insert tooth disc cutters in TBM applications.