Determination of Strain Paths in Sheet Metal Stamped Pieces: A New Improved Method

Nowadays, continuous technological advances lead the industrial world toward increasingly competitive stages. Rigorous quality control has become an unavoidable step in the chain of production. Car industry uses sheet materials to shape them into different pieces using stamping techniques. A very useful concept to characterize the formability of sheet metal samples is to obtain their Forming Limit Diagrams (FLD). This is the plot of their major principal strains that can sustain, prior to the onset of localized necking. Both experimental and numerical results in the literature have shown that the level of the FLD depends strongly on the Strain Path. In this work, we use a new system, developed in our research group, based on a fast, optical, co-ordinate acquisition device that calculates all the strain parameters of an industrial piece, to obtain the FLD of metal sheet stamped pieces, considering different strain path stages.