| Aiming at the problem of tunnel boring machine(TBM)cutterhead fatigue crack caused by long-distance single head driving and hard construction environment in long tunnel water engineering,the fatigue crack propagation life of a certain type TBM cutterhead is predicted and studied,meanwhile the structure service safety is analyzed.The structure and working principle of TBM and cutterhead are introduced.The force numerical value of disc cutter is calculated by CSM model,the finite element model of cutterhead is established,and the static and dynamic characteristics of cutterhead structure are analyzed.Under the static load,the maximum stress of cutterhead structure is 84.449 MPa,the maximum deformation of cutterhead is 1.375 mm,and the 1st to 6th natural frequencies of cutterhead are 59.249 Hz ～ 135.83 Hz,no resonance with the external load,indicating that the cutterhead design is reasonable.The temperature field calculation model of TBM cutterhead with multi-point heat source(disc cutters and main bearing)is established,the distribution law of thermal stress coupling stress of cutterhead structure is analyzed,and the optimization of cutterhead structure is carried out.After optimization,the maximum stress is reduced by 7.15%.The structural stress of TBM cutterhead is obtained,the load time history of structural stress is determined according to the normal random distribution theory,and the multi geological and multi working conditions are constructed.The load spectrum of the cutterhead in typical geology is compiled by using the rain flow counting method,which lays a foundation for further calculation of the fatigue crack growth life of TBM cutterhead.According to the existing statistical data of fatigue failure of TBM cutterhead,three critical areas of crack failure are determined.The crack growth type and law in the critical areas of fatigue crack failure are analyzed by ANSYS software,and the function expression of crack depth and equivalent stress intensity factor is fitted.According to the engineering practice,the initial crack size is determined based on the different positions of transient TBM cutterhead.The maximum allowable crack depth of the cutterhead face panel is calculated,and the damage tolerance criterion of TBM cutterhead panel is proposed.Based on the data of probability fracture mechanics and fatigue crack growth test of Q345 D material,the model of crack growth rate under different survival rate of cutterhead is established.The crack growth life of TBM cutterhead is calculated according to the load spectrum of cutterhead under typical geology,and the structural safety of TBM cutterhead is analyzed.The tracking test of tunnel construction project is carried out,and the correctness of damage tolerance criterion value and life prediction is verified.The research results provide an important reference for the fatigue life prediction of TBM cutterhead,and also provide a scientific basis for the maintenance and remanufacturing of the cutterhead. |
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