Applicability of Notch Stress-Strain Correction Methods to Low-Cycle Fatigue Life Prediction of Turbine Rotors Subjected to Thermomechanical Loads

Abstract

The paper analyses the possibility of using analytical methods of notch stress-strain correction in low-cycle fatigue life predictions of steam turbine rotors operating under non-isothermal conditions. The assessment was performed by comparing strain amplitudes calculated using the Neuber and Glinka-Molski methods and those predicted by the finite element analysis (FEA) employing elastic-plastic material model. The results of investigations reveal that the Neuber method provides an upper bound limit, while the Glinka-Molski method results in a lower bound limit of strain amplitude. In the case of rotor heat grooves, both methods provide equally accurate results of notch strain amplitude and are suited to estimating lower and upper bound limits of low-cycle fatigue life under non-isothermal conditions.

Design of step‐stress accelerated life tests for estimating the fatigue reliability of structural components based on a finite‐element approach

“…Moreover, the FE method is often the reference to check the validity of the two analytical approaches. [34][35][36][37][38][39][40] For this reason we also selected the FE approach for designing the synthetic P-S-N curves. At this point, it needs to be explained that for the complicated structures, only the number of cycles near the notch could be estimated in this manner.…”

Principles of Stress-Strength Modelling of the Highly Thermally Loaded Materials—The Influence of an Effect of Strength Differential on the Material Effort

“…Here, a key stress invariant appears for the first time [ 11 , 13 , 14 ]: where is the stress deviator. In the Western European literature, there are different notations for the relationship between invariants, , , or : or in terms of the principal stresses: …”

“…The most popular heat-resistant material used in power plants is St12T steel [ 4 , 8 , 14 , 15 , 16 , 28 ]. As mentioned in the previous section, static tensile and compressive tests were made to figure out the steel limit properties that are required for further calculations.…”

“…The main objective of the presented paper is the description of stress and strain states in highly thermally loaded materials using both the Huber–Mises–Hencky (HMH) and Burzyński effort criteria [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. The HMH approach is certainly the most commonly employed approach to capture effort evolvement.…”

Burzyński’s Criterion in the Analysis of Heat Resistant Steel

“…In the above equation 6Rer means a strength yield at stretching and Rec stands for the strength yield at compression. These values should be determined from the material tests such as static tensile test and static compression test (Banaszkiewicz and Dudda, 2018).…”