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:

${\displaystyle r={\frac {\ln(b_{1}/b_{0})}{\ln(s_{1}/s_{0})}}}$

${\displaystyle r_{m}={\frac {r_{0}+2r_{\text{45deg}}+r_{\text{90deg}}}{4}}}$

• 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 :

${\displaystyle r_{\text{eben}}={\frac {r_{0}-2r_{\text{45deg}}+r_{\text{90deg}}}{2}}.}$