Effect of ironing on the residual stresses in deep drawn cups

An experimental investigation has been carried out to determine the effect of ironing on the magnitude and distribution of the bending residual stresses in deep drawn cups. The separation method is used to determine the stresses in both the axial and the tangential directions. The independent variables of the investigation are the ironing reduction ratio, the number of ironing stages, and the metal type, the latter being St1403 and AlMg3. It was found that ironing gives a characteristic distribution of the residual stresses along the cup wall. The axial stresses decrease from a maximum near to the cup bottom to a minimum along the wall, then tend to vanish at the edge, whilst the tangential stresses are uniformly distributed along the cup wall. The residual stresses after deep drawing can be reduced greatly by ironing the cups with relatively small ironing strains. The number of the ironing stages does not affect the residual stresses significantly. The magnitude of the residual stresses, as compared to the positional flow stress of the metal, are higher in St1403 cups than those in AlMg3 cups.