Research On Fracture Behavior Of Tenon And Influence Factors Of Contact Performance In Nickel-based Single Crystal Turbine Blade

The fracture accident occurred in tenon/groove contact area pose a palpable threatto the performance of engine in nickel-based single crystal superalloy turbine blade. Soan advanced turbine blade design techniques will significantly increase the life ofcivilian and military engines. Therefore, to have an understanding of contactperformance in nickel-based single crystal superalloy turbine blade will have majortheoretical significance and engineering applications value on improving the life ofengines.Combination the methods of macroscopic and microscopic, experimental analysisand finite element simulation in this paper, the fracture behavior of the crack generatedin tenon/groove is analyzed and the influence factors of contact performance (frictioncoefficient and contact gap) are discovered.A three-dimensional model of the blade is set up to analyze the crackcharacteristic on the tenon of nickel-based single crystal superalloys turbine blade inthis thesis. The Mises stress and resolved shear stress distributions of crack tip inisotropic and {001}[110],{011}[110],{111}[110] orientations were researched andthen the crack propagation trend was examined by resolved shear stress distribution.The results show that under {001},{011},{111} conditions, the crack propagation angle is45,54.7,90respectively. It can prove that the crack propagates along aparticular direction and shaped as a serration.The macroscopic and microscopic morphology of the turbine blade with crack isobserved. The results show that the position near the exhaust side of the first toothbelongs to a relatively high-stress area and the crack will appear in this position. Themorphology is considered as the feature of fatigue. The crack propagates as a serrationand the angle between the serration is50°approximately, which can coincide with theresult of finite element analysis.Based on the theory of low-cycle fatigue, a tenon/groove contact model is set upand different friction coefficient of0,0.2,0.4,0.6,0.8,1.0are taken into account tocalculate the contact stress and fatigue life in {001},{011} and {111} orientation. Thenthe relationship between contact stress, fatigue life and friction coefficient is discussed.Take {001} orientation as example, a cubic curve is found to fit the relationshipbetween the friction coefficient and logarithmic fatigue life, and it can provide thebasis for the design of the contact surface.Contact stress and fatigue life in {001},{011} and {111} orientation is calculatedthrough changing the contact gap. The results show that contact gap has a significantinfluence on contact performance of nickel-based single crystal superalloy turbineblade. Crystal orientation is also a relatively significant role on the fatigue life, whichshowed the anisotropy of fatigue properties obviously.