Methodology to evaluate strength properties of steel by single instrumented indentation test

Abstract

The instrumented indentation test (IIT) is an attractive non-destructive testing technique. Determining accurate strength properties of steel using IIT is still challenging. In this paper, a new methodology is proposed to acquire the yield and ultimate tensile strength from a single IIT. This method extracts true stress-strain curves from IIT results. Acquired stress-strain curves indicate that the initial yield stress is not repeatable. This is caused by the inhomogeneous deformation of IIT specimens. Based on the obtained true stress-stain curves, corresponding yield strength, and ultimate tensile strength are calculated through theoretical derivation. The results show that the strength has a convergent tendency. On basis of this phenomenon, the strength is determined with an extrapolating method. Finally, the strength properties of Q345R are investigated to verify the reliability of this method. It is found that the strength determined from IIT and conventional tensile tests shows good agreement. The proposed method is effective in predicting strength properties from a single instrumented indentation test.