A non-contact optical uniaxial tension-unloading strain measurement

A tension-compression test is necessary to investigate the impact of the kinematic hardening model’s parameters on the springback following sheet metal stamping processes. However, conventional cyclic testing using extensometers faces challenges due to buckling issues. Therefore, the implementing of Digital Image Correlation (DIC), a non-contact optical measurement system, becomes crucial. The present investigation involved the simultaneous use of an extensometer and an AutoGrid optical strain measurement system to perform a uniaxial tension-unloading test on aluminum alloy AA6082-T6. Both measurement systems were evaluated based on the comparison of the time-displacement, time-force, true stress-true strain, and reduction of Young’s modulus due to deformation. The results show that the force, change in displacement, and stress-strain values obtained by the two measurement techniques are comparable and close. It demonstrates that the DIC method has high accuracy and moderate agreement with conventional extensometer.