Plastic Strain Ratio R For Sheet Metal

Volume 18 issue 4 plastic strain ratio r for sheet metal.

Plastic strain ratio r for sheet metal.

The r value is calculated from width and longitudinal strain and is a measure of sheet metal drawability. Astm e517 standard test method for plastic strain ratio r for sheet metal governs its determination. It is typically advantageous if the material reduces in area a minimal amount when subject to this force meaning a good drawing material has a high r value. This scalar quantity is used extensively as an indicator of the formability of recrystallized low carbon steel sheets.

The r value is the ratio of the true strain in the width direction to the true strain in the thickness direction when a sheet material is pulled in uniaxial tension beyond its elastic limit see figure 1. The r value is calculated from width and longitudinal strain as a test specimen is pulled in tension. 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. The lankford coefficient also called lankford value r value or plastic strain ratio is a measure of the plastic anisotropy of a rolled sheet metal.

01 july 1990 coden. It is the ability to maintain thickness as the material is drawn. It is a measure of plastic anisotropy and is related to the preferred crystallographic orientations with in a polycrystalline metal. Unlike many other materials with r values that remain constant over the range of plastic strains the r value of sheet varies with the applied axial strain and as such should be reported at the tested strain level.

Effect of gage length and width measurement locations using reduced section specimens received 24 july 1989. Accepted 28 november 1989 published online. The plastic strain ratio r is considered a direct measure of sheetmetal drawability and is useful for evaluating materials intended for forming shapes by a deep drawing process. Plastic strain ratio r is a measure of the ability of a sheet metal to resist thinning or thickening when subjected to a tensile or compressive force.

It is a measure of plastic anisotropy and is related to the preferred crystallographic orientations within a polycrystalline metal.