EN ISO 16808:2014

Foreword
1 Scope
2 Symbols and abbreviated terms
3 Principle
4 Test equipment
5 Optical measurement system
6 Test piece
7 Procedure
8 Evaluation methods for the determination of
  the curvature and strains at the pole
9 Calculation of biaxial stress-strain curves
10 Test report
Annex A (informative) - International comparison of
        symbols used in the determination of the bulge
        test flow curve
Annex B (normative) - Test procedure for a quality
        check of the optical measurement system
Annex C (informative) - Computation of the curvature
        on the basis of a response surface
Annex D (informative) - Determination of the equi-biaxial
        stress point of the yield locus and the hardening
        curve
Bibliography

ISO 16808:2014 specifies a method for determination of the biaxial stress-strain curve of metallic sheets having a thickness below 3 mm in pure stretch forming without significant friction influence. In comparison with tensile test results, higher strain values can be achieved.