Determining reliable wide-strain-range equivalent stress–strain curves using 3D digital image correlation

Abstract

We propose a method for obtaining reliable wide strain range equivalent stress–strain curves from tensile testing by applying 3D digital image correlation. Herein, both the front and side surfaces of the specimen were identified by the 45° tilting of the specimens. The deformation of the specimen was the most severe in the neck section, and the equivalent strain representing the entire specimen could be extracted from the neck regions on the side and front surfaces. In addition, the equivalent stress was obtained by calculating the reduction in the varying cross-sectional area from the strain information of the two surfaces. The resulting wide strain range equivalent stress–strain curves can describe nonlinear hardening behaviors up to higher strains than the conventional gauge length method. The proposed method can provide wide strain range equivalent stress–strain curves only through experiments without requiring separate finite element method simulations or correction factors.

Keywords

• Equivalent stress–strain curve
• Uniaxial tensile test
• Strain correction
• Stress correction
• Digital image correlation