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Abstract
The stress rupture behavior of nickel-base single crystal superalloys is a primary issue facing aero-engine design, which has been studied for more than 40 years. To a large degree, it is the existence of film cooling holes with the introduction of air cooling techniques that adds the extra challenge to the problem. Using both experimental and numerical methods, we explore here the stress rupture behavior of nickel base single crystal plate specimens subject to multi-row film cooling holes. As the numerical simulation part, finite element analysis using Abaqus was performed. Numerical results reveal that the existence of film-holes causes stress concentration and transforms local stress from uniaxial to multi-axial. For the stress distribution of different types of specimens, we defined a stress multiaxiality factor to quantitatively characterize the degree of the stress complexity and examined its effect on the rupture behaviors of the specimens along with the true stress concentration factor. The test was also carried out and results indicated that the creep rupture lives of one- and two-row specimens turn out to be longer than those of non-hole specimen. However, the three- and four-row configuration showed the opposite trend. Among the geometric parameters of film-hole configuration, film-hole row spacing is a predominant one influencing the creep rupture properties. Numerical results agree well with the fracture positions and shapes of specimens.
Highlights
In the past few decades, nickel-based single crystal superalloys (SXs) have been widely used in hot section components because of their excellent performance against high temperature creep
The objective of this paper is to investigate the effects of multi-row film-hole configuration of a second generation nickel-based single crystal superalloy DD6, both in experimental and numerical approaches
There is no clear relationship between the configuration parameters and the stress rupture lives of the corresponding specimens, quite interestingly, the changing trend of the true stress concentration factor coincides with that of the parameter d1, and there is a similar trend between the stress multiaxiality factor and the parameter d2, when comparing the figures in Table 3 of Section 4.3 and the above table
Summary
In the past few decades, nickel-based single crystal superalloys (SXs) have been widely used in hot section components (mainly gas turbine blades) because of their excellent performance against high temperature creep. Together with the anisotropy of SXs, and inherently complex nature of creep and dislocation motion in the γ/γ0 structures, this makes it the subject of numerous scientific investigations to estimate and model the mechanical properties of single crystal superalloys. Various models were proposed to explain the creep mechanism of single crystals and to predict the creep rupture lives. A viscoplastic approach was proposed to gain unique solutions [5,6,7]. Based on such plastic constitutive frame and the damage mechanics, many other models with different damage parameters were proposed [8,9,10,11,12].
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