Characterization of deformation behavior of thin-walled tubes during incremental forming: a study with selected examples

As an emerging flexible manufacturing technology, incremental forming of tubes has the ability to produce various tubular parts, including those that are difficult to integrally form using other methods. Due to the nature of hollow and thin-walled geometry, the deformation mechanism in the incremental forming of tubes is quite different from that of conventional incremental forming of sheets. This paper summarizes a list of typical tubing that can be formed incrementally and then examines the processes used to form four types of tubular parts, including axisymmetric expansion/reduction of tube ends, tube wall grooving, and hole flanging. This is done primarily from the perspective of phenomenology by using experiments and numerical simulation. Typical deformation behaviors of the workpieces were revealed and discussed. Three basic deformation modes in terms of variations in wall thickness, namely thinning (such as in end expansion), thickening (such as in end reduction), and invariant or almost constant thickness (such as in part of the wall grooving), were found to exist during incremental tube forming. Regarding the formability limits of the tube, incremental forming has its own advantages and disadvantages when compared with pressing.