Evaluation method of equivalent initial flaw size and fatigue life prediction of nickel-based single crystal superalloy
Multidiscipline Modeling in Materials and Structures
ISSN: 1573-6105
Article publication date: 17 October 2023
Issue publication date: 13 November 2023
Abstract
Purpose
The purpose of this paper is to apply the concept of equivalent initial flaw size (EIFS) to the anisotropic nickel-based single crystal (SX) material, and to predict the fatigue life on this basis. The crack propagation law of SX material at different temperatures and the weak correlation of EIFS values verification under different loading conditions are also investigated.
Design/methodology/approach
A three-parameter time to crack initial (TTCI) method with multiple reference crack lengths under different loading conditions is established, which include the TTCI backstepping method and EIFS fitting method. Subsequently, the optimized EIFS distribution is obtained based on the random crack propagation rate and maximum likelihood estimation of median fatigue life. Then, an effective driving force based on anisotropic and mixed crack propagation mode is proposed to describe the crack propagation rate in the small crack stage. Finally, the fatigue life of three different temperature ESE(T) standard specimens is predicted based on the EIFS values under different survival rates.
Findings
The optimized EIFS distribution based on EIFS fitting - maximum likelihood estimation (MLE) method has the highest accuracy in predicting the total fatigue life, with the range of EIFS values being about [0.0028, 0.0875] (mm), and the mean value of EIFS being 0.0506 mm. The error between the predicted fatigue life based on the crack propagation rate and EIFS distribution for survival rates ranges from 5% to 95% and the experimental life is within two times dispersion band.
Originality/value
This paper systematically proposes a new anisotropic material EIFS prediction method, establishing a framework for predicting the fatigue life of SX material at different temperatures using fracture mechanics to avoid inaccurate anisotropic constitutive models and fatigue damage accumulation theory.
Keywords
Acknowledgements
The research was supported by the National Natural Science Foundation of China (52105147), National Science and Technology Major Project (J2019-IV-0011–0079), and Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University (No. CX2021068).
Citation
Wen, Z., Li, F. and Li, M. (2023), "Evaluation method of equivalent initial flaw size and fatigue life prediction of nickel-based single crystal superalloy", Multidiscipline Modeling in Materials and Structures, Vol. 19 No. 6, pp. 1311-1338. https://doi.org/10.1108/MMMS-08-2023-0256
Publisher
:Emerald Publishing Limited
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