Hidden mechanical joints of sheets to rods by axial sheet bending and unbending

Abstract

Mechanical joints of sheets to rods by plastic deformation produced at room temperature away from the rod ends have been investigated in recent years but new developments are still needed. The process hereby presented relies in the axial bending of a sheet with a pre-drilled hole of smaller diameter than that of the rod, until the diameter of the sheet becomes equal to the initial diameter of the rod. Then, a rod is placed inside this larger hole diameter of the sheet and the sheet is unbent to its original shape, with its material being radially injected to a rectangular cross-section slot previously machined in the rod, thus producing a mechanical interlocking between the two geometries. The major process parameters are identified and their influence in the deformation mechanics is analysed by means of finite element modelling and experimentation. The experiments were carried out in unit cells while the numerical modelling analysed sheets of different lengths and thicknesses, so that to allow a proper understanding of the influence of different specifications on the new joining by forming process. Destructive performance tests were performed in the sheet-rod connections and comparisons with previous joining techniques were made to confirm the success of the new mechanical joint.