Optimum Design of Variable-Material Flywheels

This paper deals with design configurations that would maximize energy stored per unit mass of flywheel and would also lead to more uniform stress distribution within yield limits. A “shape factor” is herein used to relate inertia per unit mass to specific strength (viz., yield strength per unit density), the flywheel being equally stressed in both radial and tangential directions. A proposed “optimum design function” is shown to facilitate the search for an optimum design of an isotropic variable-material flywheel. Multimaterial flywheels, made up of suitable groups of materials may well provide higher inertia per unit mass than the corresponding constant-strength disk made of any material in the group. Examples of two-element alloy flywheels (lead-tin and aluminum-magnesium) with higher inertia per unit mass than the constant-strength disk are displayed.