Hardening evaluation of stamped aluminium alloy components using the Small Punch Test

The parts and components manufactured by stamping processes are accompanied by high plastic strain levels that generate residual stress and changes in the mechanical behaviour of the material in areas of high strain. An accurate design of these components requires a thorough understanding of these initial plastic strains as a result of the stamping process and its effect on the mechanical behaviour of the component. This paper analyzes the viability of the Small Punch Test (SPT) to determine the yield stress evolution in any area of stamped aluminium alloy components in those cases where there is not sufficient material to carry out standard tests. This test basically consists of deforming a miniature specimen, whose edges are firmly gripped by a die, using a high strength punch. The yield load in the SPT will be related to yield stress to provide a valid expression to evaluate the hardening of the material in any area of a stamped component regardless of the degree of strain achieved during the stamping process.

► SPT specimens with different levels of plastic strain have been tested.
► The yield stress could be evaluated without knowing the level of plastic strain.
► The presented methodology can be used with other materials used in stamped components.