Ball indentation technique - An important and useful method for studying the flow properties of materials

Abstract

The effectiveness of the ball indentation technique (BIT) has been established. BIT has been employed to explore the possibilities for revealing the effect of pre-strain and heat treatment on mechanical properties of HSLA steels and En steels. Welded HSLA steel has also been tested for finding the point to point variation (across the specimen) in mechanical properties. For all the materials tested, the yield, strength (Ys), ultimate tensile strength (UTS), strength coefficient (k) and strain hardening exponent (n) values have been derived through BIT and they are validated with the standard conventional mechanical test results. It is found that, with increasing the pre-strain effect the YS, UTS values have increased while K and n values have decreased. Across the weldments the variation of properties are consistent with the microstructural variations. The results clearly demonstrate the feasibility of this technique for determining the flow properties of the HSLA steel and their weldments as well as HAZs. Overall, it is found that BIT can be effectively used to determine the minute changes of mechanical properties either due to pre straining or due to beat treatment by using small amount of materials and it is quite fast compare to conventional test technique.