Reliability study on the fatigue life of film cooling blades in advanced aero-engine turbines: Neglected crystal orientation uncertainty in casting

The orientation uncertainty of single-crystal turbine blades is a neglected practical engineering problem, and previous research has paid little attention to it. The work innovatively presents the random distribution regularity of the spatial orientation formed in the casting of single crystal blades and its influence on the structural reliability, which establish a foundation for the orientation design of blades. In this work, the uncertain characteristics of the spatial orientation for single crystal cast blades are mathematically quantified. Meanwhile, based on the classical material constitutive and life equations, the elastic-plastic theoretical and fatigue life evaluation models related to orientation are deduced and firstly applied to turbine blade engineering analysis. The elastic-plastic stress distributions of single-crystal turbine blades considering thermal effects are obtained by the fluid-structure interaction simulation. The spatial orientation distribution characteristics is presented from analyzing hundreds of samples. Finally, the influence of the uncertain orientation on the low cycle fatigue life reliability and structural failure probability of single-crystal turbine blades are clarified for the first time by using the BP neural network and stepwise response method. Our results demonstrate that crystal orientation uncertainty, especially in long-life design, can cause a serious failure probability, proving the necessity of orientation control for single crystal turbine blades clearly.