Abstract: Functionally graded materials(FGMs) are new materials whose properties change continuously in the spatial position. Using FGMs instead of uniform materials for high speed energy storage flywheel rotor can reduce stress concentration effectively and give full play to the material properties, thereby improving the rotor performance . In view of the big error of plane stress(PS) solution when the axial thickness of flywheel rotor is big compared to its radius, a three-dimensional semi-analytical solution that is a modified plane stress(MPS) solution of FGMs flywheel rotor is derived by dividing the rotor into finite ring elements with constant thickness and homogeneous material, and then its accuracy is verified by finite element method. At last, by taking thickness, material volume fraction and rotating speed as design variables, and maximized energy storage density of the rotor as objective function, both shape and material distribution are optimized for FGMs flywheel rotor by using sequential quadratic programming(SQP) method, in addition, the effect of material properties on optimization results are also analyzed. Calculation results indicate that rational shape and material distribution can make stress distribution more even, and greatly increase the energy storage performance of flywheel rotor.

Key words: Sequential quadratic programming(SQP), Flywheel rotor, Functionally graded materials(FGMs), Modified plane stress(MPS)