MECHANICAL TESTING

Plastic Strain Ratio r for Sheet Metal - ASTM E 517

ASTM E 517 covers special tension testing for the measurement of the plastic strain ratio, r, of sheet metal intended for deep-drawing applications.

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 with in a polycrystalline metal. This resistance to thinning or thickening 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.

Index of Mechanical Testing