Numerical simulation of damage for Cr35Ni45Nb steel ethylene cracking furnace tube at action of coupled multiple factors

Based on the continuum damage mechanics (CDM), a user subroutine of ABAQUS coded by FORTRAN was developed for simulating the damage process of Cr35Ni45Nb steel ethylene cracking furnace tube at action of coupled creep-carburization under 1050°C. The results showed that the inner surface of tube generated micro-cracks firstly at action of coupled creep-carburization. However, the rupture initiated from the outer surface at action of single creep. The Von-mises stress and maximum principal stress along the inner surface decreased initially and then increased with time at the action of single creep. And the Von-mises stress and maximum principal stress along the outer surface increased with time, which caused the damage rate of outer surface to be higher than that of inner surface. The Von-mises stress and maximum principal stress along the inner surface decreased with time at action of coupled creep-carburization, which was contrary to the outer surface.