A review of stress analysis on materials and structures for flywheel energy storage systems

With advantages such as high power density, long cycle life, and environmental friendliness, flywheel energy storage systems hold great promise in applications like renewable energy integration and grid frequency regulation. As the core component for energy storage, the rotors stress distribution and evolution under high-speed rotation directly affect the systems safety and reliability. This paper reviews the stress analysis of rotor materials and structures in flywheel energy storage systems, systematically summarizing current research progress. First, from the perspective of material constitutive properties, it compares the stress responses of conventional metals (e.g., steel and aluminum alloys) and high-performance composite materials (e.g., carbon fiber-reinforced polymers and metal matrix composites) under centrifugal loads, with a focus on the failure mechanisms of anisotropic materials, high-cycle fatigue stress, and thermo-mechanical coupled stress. Second, in terms of structural design, it explores the influence of topology optimization, thin-walled hollow structures, and stiffener configurations on stress concentration and distribution within the rotor, and elaborates on the complex evolution of stress fields under multi-physics coupling (centrifugal force, temperature, and electromagnetic fields). Furthermore, it summarizes the current applications of finite element simulation, experimental methods (strain gauges and digital image correlation), and multi-objective optimization in stress analysis. The study shows that although existing research has revealed the critical influence of material and structural parameters on stress, challenges remain in areas such as refined modeling of multi-field coupling, integrated material-structure optimization, and full lifecycle stress prediction. Future research should integrate the development of novel materials with intelligent design approaches to deepen the understanding of stress mechanisms and provide theoretical support for the lightweight and high-reliability design of flywheel energy storage rotors for engineering applications.