Standard Test Method for Plastic Strain Ratio r for Sheet Metal
The plastic strain ratio r is a parameter that indicates the ability of a sheet metal to resist thinning or thickening when subjected to either tensile or compressive forces in the plane of the sheet. It is a measure of plastic anisotropy and is related to the preferred crystallographic orientations within a polycrystalline metal. This resistance to thinning or thicken-ing contributes to the forming of shapes, such as cylindrical flat-bottom cups, by the deep-drawing process. The r value, therefore, is considered a measure of sheet metal drawability. It is particularly useful for evaluating materials intended for parts where a substantial portion of the blank must be drawn from beneath the blank holder into the die opening.
