Local forming of gears by indentation of sheets

The aim and objectives of this article are to provide an analytical model for the incremental forming of gears along the direction perpendicular to the sheet thickness. The model allows determining the influence of the major process parameters in the indentation force and in the material volume undergoing plastic deformation during indentation by means of double-wedge gear tooth punches. Special emphasis is placed on the influence of superimposing tension stresses along the in-plane direction. The analytical model is built upon the slip-line theory under plane strain deformation conditions, and results are compared against those obtained from experiments in DC04 mild steel and from numerical simulations performed with the finite element method. Results show that the indentation force can be significantly reduced by stress superposition, and that a minimum distance from previous indentations is necessary to produce a new gear tooth in a material free from residual strains and stresses.