The Analysis of the Continuous Fracture Process of the Steam-Turbine Rotor with the Local Defect

Abstract

Main factors that determine the steam-turbine rotors work lifetime which work in a long-term load circumstances under an influence of high temperatures are the accumulation of creep deformations and the concomitant accumulation of the damage of the material. The heterogeneity of the material leads to the nascence of the defect that is the concentrator of stresses. To describe the dispersed damages impact on the construction material strength the function of the damage is applied the value of what changes during the operation process. To perform the research discrete models with N = 235, N = 731 and N = 2047 are considered. Using thicker discrete models allows clarifying the rotor basic lifetime value on 2% and 1% respectively. For the finite-element model with N = 731 the rotor basic lifetime value in the presence of the defect is 104000 hours that is less by 15% than in the absence of the defect. The rotor additional lifetime value is 6000 hours. The maximum value of the damage parameter can be observed on isolines nearby the defect at the moment of time 2200 hours and the difference between maximum values of the damage parameter for the rotor with the defect and hereunto is 30% that increases over time to 70%. After 104000 hours the accumulation region of the maximum values of the damage parameter increases in both directions of the rotor cross-section over time in such way that the augment of the maximum values of the damage parameter occurs more intensively in the rotation axis direction. At the moment of time 107000 hours the correlation between dimensions of the continuous fracture region in axes directions is 2/3 and to the moment of time 110000 hours is about 1/2. The value of the damage parameter in finite elements those border with the fracture region doesn’t exceed 0,3 scilicet the accumulation of the damage is local.