Abstract
Combined high and low cycle fatigue (CCF) generally induces the failure of aircraft gas turbine attachments. Based on the aero-engine load spectrum, accurate assessment of fatigue damage due to the interaction of high cycle fatigue (HCF) resulting from high frequency vibrations and low cycle fatigue (LCF) from ground-air-ground engine cycles is of critical importance for ensuring structural integrity of engine components, like turbine blades. In this paper, the influence of combined damage accumulation on the expected CCF life are investigated for turbine blades. The CCF behavior of a turbine blade is usually studied by testing with four load-controlled parameters, including high cycle stress amplitude and frequency, and low cycle stress amplitude and frequency. According to this, a new damage accumulation model is proposed based on Miner’s rule to consider the coupled damage due to HCF-LCF interaction by introducing the four load parameters. Five experimental datasets of turbine blade alloys and turbine blades were introduced for model validation and comparison between the proposed Miner, Manson-Halford, and Trufyakov-Kovalchuk models. Results show that the proposed model provides more accurate predictions than others with lower mean and standard deviation values of model prediction errors.
Highlights
Modern aircraft engines tend to meet the requirements for high thrust-to-weight ratio and high reliability [1,2]
Tests by a trapezoidal wave presented in Figure 3; the sinusoidal wave results from in-flight vibrations which give rise to high cycle fatigue (HCF) shown in the load spectrum of the cycle fatigue (CCF); based on this, the experimental lives of turbine blades can be obtained under different high-frequency vibration loads by superimposed
A generic procedure for HCF design and verification is explored, fatigue damage accumulation methods for CCF life prediction are analyzed for turbine blades
Summary
Modern aircraft engines tend to meet the requirements for high thrust-to-weight ratio and high reliability [1,2]. LCF loads result from the takeoff-cruise to landing engine cycles, HCF loads result from the aerodynamically in-flight vibrations [24] Both of HCF and LCF usually induce failure of turbine blades, which is named as combined high and low cycle fatigue (combined cycle fatigue (CCF) in this analysis) of aircraft gas turbine blades. From the viewpoint of turbine blade design, the effect of superimposing LCF to HCF needs to be considered through modeling the combined damage accumulation on the expected fatigue strength behavior by CCF tests [25]. Through characterizing the effects of high cycle stress amplitude and low cycle stress amplitude on combined fatigue damage, Zheng et al [36] developed a CCF life prediction model based on the exponential decay law. The proposed model is verified with five experimental datasets of turbine blade alloys and turbine blades comparing with three other models in Section 4; Section 5 gives a conclusion to this paper
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