Determination of crack resistance of a steam turbine rotor under the volume forces action

Abstract

The problem of the crack resistance of a steam turbine rotor disk with an initial semi-elliptical crack is investigated in this paper. The forces affecting the disk are due to its rotation and consist of a load uniformly distributed of the surface rim, modeling the impact of the blades, and mass forces distributed over the volume of the disk. It is assumed that the process of deformation of the rotor disk is linear. The stress intensity factor (CIF) are used to evaluate the fracture resistance. The steam turbine rotor disc is a massive axisymmetric body, which is why a semi-analytic finite element method is used to model the stress-strain state, which has been proven in a number of work for objects of this type. In the first stage, the distribution of stress-strain state of the rotor disc without crack is determined. The obtained results showed that maximum stresses occur in the region of the inner hole of the rotor disk. The following was to determine the fracture resistance of the rotor disc with a crack that may appear under the highest stress level. The configuration of the crack front is elliptical. The obtained results shows that the CIF attains the maximum value at the point furthest from the inner hole. The influence of ellipticity on the maximum values of CIF was investigated. The maximum CIN values for the rotor disc were determined using the approximate method used in the design of such objects. It involves the results of the known formula used to determine the CIF in the plate with a lateral crack. Comparison of results shows the nesecity of calculate such objects in the spatial formulation. There are significant limitations to the use of the two-dimensional approach to determine CIF in such objects.