Design and optimization of shaft–hub hybrid joints for lightweight structures: Analytical definition of normalizing parameters

This paper addresses the design and optimization of interference-fit and adhesively bonded joints (hybrid joints) in lightweight structures. These types of joint involve a hub and a solid or hollow shaft, locked together by a frictional force (based on the radial pressure and the Coulomb friction law) and an adhesive strength generated at the coupling surfaces. The total strength of the joint allows the transmission of axial forces or torque moments. This paper amply investigates the optimal combinations of the hub aspect ratio (ratio between internal and external diameters) in order to maximize the axial (or torque) load transmitted by the joint as well as to reduce the weight of the structure. Derived from an analytical approach, two normalizing parameters are employed which are able to take into account the simultaneous effect of the materials density, the shaft aspect ratio, the hub yield strength, the coefficient of friction between the mating parts and, finally, the adhesive mean strength. Some design formulae and charts, based on the maximum shear yield criterion (Tresca), are proposed as a function of such normalizing parameters.