An investigation on the accuracy of numerical simulations for single point incremental forming with continuum elements

Finite element methods (FEM) have been widely used in simulating the single point incremental forming (SPIF) process to investigate the effects of process parameters, such as incremental depth, tool size and tool path on the thickness/strain distributions, deformed shapes, and the formability. However, due to the complexity of the process and the continuous change of the contact area in SPIF, numerical simulations tend to be time-consuming and hard to converge when an implicit integration method is used. To meet these challenges, most simulation work found in literature utilized the explicit integration method with shell elements to simulate the SPIF process. However, results have not been found satisfactory as evident by mismatches of the predicted shape, strain/thickness distribution and/or forming force between simulation and experimental results. In our past work, in order to obtain a more accurate result and consider the contact force in the thickness direction, solid continuum elements were introduced combined with the implicit method. Although the trends of the forming force in the Z direction were very similar between simulations and experimental results, there still existed a relatively large discrepancy in absolute values. In this paper, effects of yield criterion, element size and element type on the predicted forming force are investigated. Additionally, a new damage model has been incorporated into FEM simulation that, for the first time, predicts the force curve, the location of fracture and the maximum thinning with remarkable accuracy.