621.165:539.4 and N. G. GarmashWe present the results of numerical analyses (in the three-dimensional statement) of the kinetics of stressed state and accumulation of dispersed defects in the zone of discharge holes in the rotor disks of a steam turbine in creep for 400,000 h . It is shown that the zones of discharge holes in the disks of the first two stages suffer the action of the highest stresses and the material in these zones is damaged more intensely that near the surface of the axial channel.Keywords: rotor, discharge holes, creep, damage to the material, long-term strength.Parallel with the surface of the axial channel, disk fillets, fillets of the root joints, and temperaturecompensating grooves of the end and diaphragm seals, the zones of discharge holes in the disks of the first two stages of solid-forged rotors of high-pressure (HPC) and medium-pressure cylinders (MPC) of steam turbines are regarded as the most critical sites from the viewpoint of exhaustion of their service life. Indeed, the rotors are most often damaged just at these sites [1,2]. In view of the severe consequences of possible failures, the high-temperature zone of the axial channel proves to be especially dangerous. In estimating the service life of rotors, special attention is given to the temperature-compensating grooves and disk fillets because, in these zones, the metal operates under severe conditions and is damaged as a result of both creep and thermal fatigue in the nonstationary modes. In the branch standard [3] regulating the numerical analyses of the total and residual service life of the rotors of steam turbines, the zone of discharge holes is neglected.The analysis of the accumulated numerical results shows that, near the surface of the axial channel, in the zones of discharge holes and in the rims of disks at the sites of steam inlet, the defects are mainly accumulated according to the mechanism of creep in the stationary modes of operation. In these zones, it is reasonable to determine the long-term static strength according to the branch standards [4,5] in which the safety margins are specified for the computed nominal equivalent stresses relative to the long-term ultimate strength.Among highly stressed zones of the rotors, the zone of discharge holes remains studied quite poorly. In finding the stress-strain state (SSS), the discharge holes are regarded as stress concentrators. Moreover, it is recommended [4] to determine local stresses for these holes by using the nominal hoop and radial stresses obtained from the solution of the plane problem of thermoelasticity for disks or the values determined from the solution of the axisymmetric problem and averaged over the thickness. In this case, according to [3], it is recommended to decrease the safety margin for long-term strength n lt from 1.5 to 1.35 (by 10%).In [6], the long-term strength of the medium-pressure rotor of a K-300-240 LMZ turbine was studied in the zone of discharge hole in the disk of the first stage (T =°525 C) according to the recommendations mad...
