The extension of the surface of a sheet in all directions. In stretching, the flange of the flat blank is securely clamped. Deformation is restricted to the area initially within the die. The stretching limit is the onset of metal failure. The n in the equation = Kn which equates the true stress to the true strain of a material under plastic deformation. The n-value is measured from a tensile test by finding the slope of the true-stress to true-strain in the plastic region. It is also referred to as the n-value.