Numerical Simulation And Research On The Welding Process Of The Cutterhead’s Typical Position

The cutterhead of shield machine, consisting of hundreds of welding seams, belongs to large welded structure. Weld crack is one of the major failure modes during its normal work process. Welding residual stress and distortion distributed in these welding seams have a big influence on the fatigue life and structural stability of the cutterhead. The force analysis of the cutterhead during the normal working condition is completed by the ANSYS finite element software. The stress distribution of the simulation result shows that the maximum stress distribute on the welding seams and their neighborhood regions of the connection part between the cutterhead and the flange plate. they are also the positions that prone to cracking according to the cutterhead failure incident reports. So, we consider those positions as the typical positions of the cutterhead in this paper. Based on the finite element theory and the thermal elastic-plastic finite element method, a finite element model of the typical positions that contains multi-layer and multi-pass CO2Arc welding seam is created to simulate the welding process. Then the temperature field, the stress field and the corresponding residual stress and distortion can be obtained by the simulation results.Based on the muti-layer and muti-pass CO2Arc welding thick plate, the double-ellipsoid heat source model was adopted to simulate the welding heat source. The convection situation of different position are also discussed and handled. The simulation results show that the element birth and death technology which activates the welding beams’elements step by step can simulate the forming process of the welding beams during the welding process accurately. The temperature field of the model and the thermal cycling curve of some typical positions of the model are discussed and analyzed. The temperature field is adopted as the load of stress and strain analysis by using the direct coupled method. All the component of the stress including von misses stress, X, Y and Z component of stress from all the position of the model during the welding and cooling down process are available, so do the X, Y, Z component of displacement and the total distortion of the model. The research results of this paper have a guiding significance for studying the bonding technology of the cutterhead of shield machine.