Experimental and numerical study of the ironing of stainless steel cups

An experimental study of the ironing of austenitic stainless steel cups has been undertaken to (i) quantify the discrepancy (due to tool deformation) between nominal die-punch gap and real final wall thickness; and (ii) to de termine the maximum reduction for safe operation of the process. An analyti cal model has been derived in which the stresses based on the slab method, known to be very efficient for thin products, are augmented for shearing en ergy at the entry and exit of the deformation zone. A friction-factor model has been chosen to represent friction due to the rather large normal stres ses involved, and work-hardening has been included in a very simple yet eff icient way. The comparison of predicted forces with experimental forces is quite satisfactory. Moreover, finite-element modelling has been used to che ck the analytical model giving excellent agreement, proving that the remain ing discrepancies between theory and experiment are mainly due to the frict ion factor and/or constitutive behaviour used. From the FEM results, the st ates of stress in the cup wall during and after drawing are analyzed and su pport the hypotheses of the analytical model. The maximum reduction is disc ussed in terms of necking and fracture criteria (the Swift and the Hill cri teria) and compared with experimental findings. (C) 1999 Elsevier Science S .A. All rights reserved.