| Cutterhead is the main rock breaking tool of tunnel boring machine(TBM).It directly contacts with the rock.The working environment is poor and the load is complex.It is easy to be damaged,which leads to safety problems in tunnel construction.The fatigue life of cutterhead consists of crack initiation life and crack propagation life,and the crack initiation life accounts for a large proportion of the fatigue life.Therefore,it is very important to predict the crack initiation life of cutterhead to ensure the safe construction of cutterhead.This paper takes a certain type of TBM cutterhead as the research object,and studies the life and influencing factors of the cutterhead fatigue crack initiation through theoretical and simulation analysis.Firstly,according to the actual structure size of a TBM cutterhead and cutterseat,the three-dimensional model of TBM cutterhead and cutterseat is established.The static analysis is carried out by using the finite element analysis software,the stress and displacement changes of the cutterhead and cutterseat are obtained.The dangerous locations of the crack initiation cutterhead and the cutterseat are determined,which are five dangerous points on different blocks of the cutterhead and the corner of the "L" shape of the cutterhead.Secondly,using ABAQUS software,a 19 inch hob rock breaking simulation dynamic model is established.Through the dynamic rock breaking simulation analysis of the cutter,the force of the cutter is obtained.According to the CSM theory,the correctness of the model is verified.The load data of the dangerous points of the cutterhead is statistically processed,and the 8-level load spectrum of the cutterhead driving in the typical stratum is compiled,It lays a foundation for the prediction of crack initiation life of TBM cutterhead.Thirdly,based on the traditional nominal stress method,considering the stress concentration,size and surface processing,the S-N curve of Q355 B is modified.Combined with the fatigue damage accumulation theory and the 8-level load spectrum,the prediction models of the crack initiation life of the cutterhead and cutterseat with different survival rates are established.The calculation results show that when the survival rate is 50%,the crack initiation driving mileage of the cutterhead is longer 1.30 km.The software n Code is used to establish the fatigue simulation process.The error between the simulation results and the theoretical analysis results is 14.08%,which verifies the correctness of the prediction model of the cutterhead crack initiation life.Finally,the influencing factors of the crack initiation life of the cutterhead and cutterhead are studied.The results show that the stress concentration factor and load factor are inversely proportional to the crack initiation life of the cutterhead,and the size factor and surface processing factor are positively proportional to the crack initiation life of the cutterhead.The research results provide a theoretical basis for the anti fatigue design of TBM cutterhead,the formulation of manufacturing process,the adjustment of tunneling parameters in construction,the key detection parts of cutterhead and the reasonable arrangement of maintenance cycle,which has a certain engineering practical value. |
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