R value (material test)
The r-value (also perpendicular anisotropy ) situated in the materials technology , a dimensionless measure of the anisotropy of plastic deformation in sheet samples. The r-value can according to DIN EN ISO 10113 in uniaxial tensile test are determined.
calculation
The mean r-value is calculated using the following equations:
- r-values> 1: width direction is main flow direction
- r-value = 1: isotropy of the material
Typical r values for steels are in the range from approx. 0.8 to 2.2.
The isotropy of sheet metal is important for the behavior during deep drawing , for example in the manufacture of beverage cans or car body parts .
The distribution of the r-values over the plane of the sheet ("lobes") is represented by the plane anisotropy :