Multiple cracks failure rule for TBM cutterhead based on three-dimensional crack propagation calculation

Practically, there is multiple cracks interpenetrating in TBM cutterhead, which gives rise to its failure prematurely. While the existing theoretical formulas and calculating methods cannot calculate its fatigue failure process under dynamic loading. In view of such situation, crack cutting sampling of TBM cutterhead after service and its fracture failure analysis were performed to clear that its fracture failure is mainly brittle fracture, based on which, A three-dimensional finite element crack propagation model was established to calculate the crack propagation process under dynamic loading. Stress intensity factor of compact test specimens is calculated by standard formula, and the growth paths of crack are got from multiple cracks fatigue tests, compared the two results obtained above to verify respectively the accuracy of the proposed method in calculating stress intensity factor and its growth path. It is confirmed that the two results about the change of stress intensity factor is basically match, and the maximum error of the growth path of the multiples crack model and the test result is about 3.7% within the permissible range. It is proved that the proposed method is feasible to calculate the multiple cracks failure process under the dynamic loading. Finally, the growth processes of collinear multiple cracks, parallel multiple cracks, nonparallel multiple cracks, and penetrating multiple cracks were calculated. The results show that the stress intensity factor at the intersection of collinear cracks decreased by about 26%, compared with a single crack. Parallel and non-parallel multiple cracks are attracted to each other as the cracks propagate in the process of growth and the stress intensity factor gradually decreases. Although the growth path and stress intensity factor do not change, the crack stops expanding, with the crack tip penetrates through another crack. The failure criterion of TBM cutterhead and the rule of interpenetration of multiple cracks proposed in this paper are the theoretical basis and technical support for the its life prediction and risk prediction.