619 / 2019-01-20 23:20:58

Fatigue crack growth simulations of steam turbine components under cyclic thermal-mechanical loads by 3D extend finite element method

Steam Turbine, fatigue crack growth, cyclic thermal load, extend finite element method

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Under frequent startup and shutdown, the high temperature and pressure components in steam turbine such as casings, rotors and valves may have crack initiation and crack growth due to the cyclic thermal-mechanical loads. After the finding of cracks in a steam turbine cylinder, the direction of crack propagation and the residual life need to be predicted. The extended finite element method (XFEM) has advantages in replicating the discontinuity of the displacement field across the crack surface and the singularity at the crack front without the need for re-meshing, thus becomes a popular fatigue crack growth simulation method in the last decade. In this paper, fatigue crack growth simulation of steam turbine cylinder under cyclic thermal-mechanical load is accomplished by three-dimensional XFEM. First, the thermal-mechanical coupled 3D XFEM is studied and achieved under ABAQUS software. Then, the stand test of fatigue crack propagation rate is carried out with CT specimen. Meanwhile the crack propagation simulation of the same specimen is done using 3D XFEM. The simulated crack growth rate is in good agreement with the experimental result. Finally, the direction and the rate of crack propagation of the cylinder are gained by the thermal-mechanical coupled 3D XFEM. The simulation shows that the residual life of the cracked cylinder of steam turbine can’t meet the need and the cylinder has to be repaired.