Improving bistable properties of metallic shells using a nanostructuring technique

A localized nanostructuring approach is proposed to manufacture bistable metallic shells and improve bistable properties of conventional cylindrical bistable shells. The stable configurations and transition processes of bistable shells based on three different mechanisms are experimentally and numerically investigated. Compared to conventional bistable cylindrical shells produced by plastically bending, the bistable shells with a nanostructured region can have much higher load bearing capacities and stiffness, and consume more energy before shape transition, no matter in a domelike shape or a cylindrical shape. Numerical modelling is developed using two equivalent inelastic strains for the plastic bending deformation and accumulated plastic deformation in nanocrystallization process. For nanostructured bistable shells, the internal stress fields are found to play important roles for the transition features, which are considerably affected by eccentric loading, while the eccentric loading has little effect on transition processes of the cylindrical bistable shells made by plastically bending. The influences of the size of the nanostructured region, the plate thickness and different nanostructuring processes on the bistable behaviors are further experimentally studied. In addition, the bistable properties of the bistable shells based on different mechanisms after thermal treatment from 200 °C to 700 °C are investigated. The applied nanostructuring process largely improves the bistable properties of bistable metallic shells, which can sustain severe environment of high temperature (about 500 °C).