A New Empirical Life Prediction Model for 9–12%Cr Steels under Low Cycle Fatigue and Creep Fatigue Interaction Loadings

Abstract

Low cycle fatigue (LCF) and creep fatigue interaction (CFI) loadings are the main factors resulting in the failure of many critical components in the infrastructure of power plants and aeronautics. Accurate prediction of life spans under specified loading conditions is significant for the design and maintenance of components. In the present study, various LCF and CFI tests are conducted to investigate the effects of temperature, strain amplitude, hold time and hold direction on the fatigue life of P92 steel. To predict fatigue life under different experimental conditions, various conventional life prediction models are evaluated and discussed. Moreover, a new empirical life prediction model is proposed based on the conventional Manson-Coffin-Basquin (MCB) model. The newly proposed model is able to simultaneously consider the effects of temperature, strain amplitude, hold time and hold direction on predicted life. The main advantage is that only the known input experimental parameters are required to perform the prediction. In addition to the validation made through the experimental data of P92 steel conducted in the present paper, the model is also verified through numerous experimental data reported in the literature for various 9–12% Cr steels.

Numerical and Experimental Assessment of the Effect of Residual Stresses on the Fatigue Strength of an Aircraft Blade

“…The next step in the performed research was to determine the stress level and prepare the ε-N fatigue models (Manson-Coffin-Basquin equation) [17][18][19][20]30] and models of cyclic hardening (for the Ramberg-Osgood equation) [23,31]. As part of the previous tests [30,31], it was determined that in the case of resonant vibrations of the compressor blade of the PZL-10W engine with a geometric notch with a depth of 0.5 mm located at a height of 3 mm from the blade root, with a known vibration amplitude A = 1.8 mm, the equivalent (Von-Mises) stress reached the highest value in the bottom of the notch, and it amounted to σ eqv = 987 MPa.…”

“…To prepare a wide range of numerical tests, based on the available literature, 8 fatigue material models were selected for the Manson-Coffin-Basquin equation, based on the numerical fatigue ε-N analysis, which was carried out. The following fatigue models were used in the analysis: Manson's, 4-point Manson's, Mitchell's, Muralidharan-Manson's, Baumel-Seeger's, Ong's, Roessle-Fatemi's, and Median's [17][18][19][20]30,31]. Detailed data on fatigue models were included in Appendix A.…”

“…The value of the residual stresses was determined using X-ray diffraction. Additionally, based on the literature fatigue models for the material used [17][18][19][20][21] and the models of cyclic hardening [21][22][23][24][25][26], the fatigue life of the blade was numerically estimated. The results of the numerical fatigue analysis were compared with the experimental results presented in the publication [27].…”

An Analysis of a Reheater Failure and a Proposal to Upgrade the Device Design

“…Boiler installations built in the 1990's are more and more often operated under a higher risk of damage to pressure elements. Due to the time of to-date service, and the large number of shutdowns and start-ups, the number of failures has been on the rise annually [1][2][3][4].…”

“…Additionally, a combination of low-cycle and creep fatigue is the main factor resulting in the failure of many critical components in the power plant infrastructure. To predict fatigue life under different experimental conditions, various conventional life-prediction models are evaluated and discussed [2]. Thermal expansion, high pressure, and temperature also shorten the life of reheaters and superheaters [3].…”