Improvement of accuracy in a free bending test for material characterization

• The free bending test is influenced by the anticlastic curvature.
• 2D numerical simulations (plane stress, plane strain) are not accurate.
• Correction factors have been developed to allow the use of 2D models.
• Material characterization procedure using bending test is presented.
• Quick and simple method for bending-dominated forming proceses.

The effect of secondary (anticlastic) curvature and the stress state on the measurement of material properties in a free bending test is studied in order to improve the accuracy of the test. Experiments and numerical analysis are conducted on a medium strength 304L stainless steel and high strength dual-phase steels, DP780 and DP1000. The dependence of the secondary curvature on sample geometry is analysed and correction factors are introduced to improve the accuracy of the calculation of material properties when using plane strain or uniaxial stress two-dimensional assumptions.A free bending test procedure is proposed to characterize material behaviour close to yield. This will allow the quick and simple analysis of material properties for bending-dominated forming processes such as roll forming.