Joining by boss forming of rods and tubes to sheets

Abstract This work presents a new joining by boss forming process for fixing rods and tubes to sheets. Material in the outer radius of the rod or tube wall thickness is axially compressed and piled up to form an annular flange with controlled cross-section geometry and size. The annular flange is then used to secure a sheet and to allow a form-fit mechanical interlocking to be obtained between the rod and the sheet by means of a second boss forming operation or an upsetting of the free tube end against the sheet surface. This paper identifies the major operating parameters and the workability limits of the boss forming process that is needed to produce the required rod-sheet or tube-sheet joints. The presentation covers material flow and tool design and is supported by experimentation and numerical simulation using finite element modelling. The new joining by boss forming process allows fixing dissimilar materials at room temperature, avoids the use of addition materials or adhesives and produces joints that are easy to disassemble at the end of the product life.