Turbine blade arc tenon/mortise structure and optimization method based on parameterized mesh deformation

An arc tenon/mortise assembly is designed and optimized based on the free-form deformation (FFD) technique. Traditional tenon connection structure with planar-to-planar contact is prone to fretting fatigue due to the action of centrifugal loading and vibration. Therefore, a novel tenon connection structure with arc-to-arc contact is developed and its fretting fatigue is analyzed by using finite element (FE) method. The result shows that arc tenon structure can decrease the stress concentration and thus improve the fretting fatigue performance effectively. Then, an optimization method is applied to improve this merit of the arc tenon further. However, FE calculation is highly dependent on mesh quality, especially the mesh size of the contact region. In addition, the mesh quality of automatic mesh-regeneration in the optimization procedure has less controllability. To preserve the mesh quality during optimization process, a mesh parameterization method is presented by establishing mapping relationship between the control points and the geometry parameters based on FFD technique, and the quality of the morphed mesh is consistent with the original. Subsequently, with combination of the design of experiment (DOE) method and Kriging surrogate model, the designed arc tenon/mortise connection structure is optimized. The results show that the von Mises stress distribution in contact region become more uniform and the fretting fatigue is about twice as much as that of its counterpart with planar-to-planar structure. It is noted that the work developed in this paper can improve the fretting performance of connection structure effectively.