Evaluation of the influence of anisotropic properties of single-crystal turbine blades of aircraft turbofan engines on their long-term strength

Abstract

Long-term static strength is one of the most important parameters to be calculated at the life-time design stage of aircraft engine turbine blades. The importance of studying and modeling this parameter is based on many factors. In particular, it should be noted that one of these factors is the peculiarities of the anisotropic characteristics of single-crystal turbine blades made of nickel heat-resistant alloys for a wide temperature and power load range. Another important factor is the different crystallographic orientations of the single crystals. The analysis of the literature has shown that to date, there are no general unified approaches for assessing the long-term strength of single-crystal turbine blades. The main approaches described in scientific literature include micromechanical (physical, crystallographic) and phenomenological models for assessing the durability of structures made of single-crystal heat-resistant nickel alloys. Many proprietary methods have also been developed in the scientific community. The majority of existing approaches, which are described in several literature sources, have many advantages and disadvantages. In this study, we propose a comprehensive approach for calculating and evaluating the long-term strength of single-crystal gas turbine blades. The proposed algorithm is based on obtaining the equations of the Larson-Miller parameter distribution by approximating the literature experimental data for different crystallographic orientations of turbine blades. The basis for numerical modeling of the distribution of the Larson-Miller parameter over the volume of the turbine blade was the calculation of creep according to Norton’s law. The equations of the Larson-Miller parameter for different crystal orientations obtained during the approximation were used in the finite element modeling of its distribution on the example of a cooled high-pressure turbine blade. Calculations were performed using the capabilities of the ANSYS Workbench software package. Based on the computation results, the time-to-failure was modeled for different crystallographic orientations and temperature states of the blade.

Keywords

• скінчено-елементне моделювання
• анізотропія
• монокристалічний сплав
• кристалографічна орієнтація
• повзучість
• довготривала міцність
• параметр ларсона-міллера
• лопатки турбіни
• авіаційний двигун