Experimental study and FEM analysis of redundant strains in flow forming of tubes

Flow forming, as a kind of metal spinning processes, is mainly used to produce thin-walled high-precision tubular components. In this study a coupled set of experiments and numerical simulations using the commercial finite element code ABAQUS/Explicit was used to study the evolution of redundant strains in a single-roller flow forming process in one pass. The modified embedded pins were used to evaluate the shear strains. It is shown that high shear strains occur not only at the longitudinal but also at the cross section. Sketched longitudinal lines also show that epsilon(theta z) of the cylindrical coordinate system cannot be neglected. Beside of the shear strains, reversal straining is recognized as another type of redundant work. It is shown that this type of redundant strain results from the incremental nature of flow forming process in which the deformation is highly localized. Good agreements between the force measurements of frictionless model simulations with the experiment imply that the frictional work can be neglected in comparison to the redundant work. (C) 2009 Elsevier B.V. All rights reserved.