Abstract: To accurately predict the fatigue and service life of the welded area of the fullface tunnel boring machine (TBM) cutterhead, the notch stress method is adopted to study the fatigue and service life of the welded area based on fatigue cumulative damage. First, a simplified model is established for the cutterhead within the allowable range of error, the cutterhead working conditions is analyzed briefly, and the external excitation loads is obtained by programming. Second, the adaptability of the notch stress method on the cutterhead welding structure is analyzed, the transient dynamics simulation is performed on the entire cutterhead to obtain the dangerous area (rib). Moreover, the virtual notch radius method is used to establish a TBM cutterhead rib model to better reflect the detailed characteristics of the weld. Then the submodel simulation analysis is performed, and the stress at the weld root in the result is used as the fatigue assessment factor. Finally, the service life of the welded structure is conservatively estimated based on the revised SN curve combined with the revised average stress. The results show the following: (1) The fatigue and service life of the cutterhead can be accurately predicted by the notch stress method. The fatigue and service life of the ribs is at the root of the weld(minimum N=2.326×107). When the cutting distance of the cutterhead is about 21.9 km, the welded joint will take the lead of fatigue failure. The calculated results coincide with the actual situation. (2) During the tunneling process of TBM, the welding area of the cutterhead is prone to different degrees of fatigue failure, causing the TBM to lose its working ability in advance and a large amount of unnecessary losses in the project.

Key words:

tunnel boring machine cutterhead welded structure, notch stress method, finite element simulation, fatigue and service life prediction