Trials Using Instrumented Indentation Technique (IIT) for Tensile Properties Determination

ABI or IIT

TWI’s Members recently requested an evaluation of the instrumented indentation technique (IIT). IIT is claimed to be capable of determining tensile properties from a local indentation similar to a hardness test. TWI subsequently investigated the capability, usefulness and limitations of the IIT and some of the findings are reported here. IIT is sometimes known as ABI (automated ball indenter) testing. There are many manufacturers of IIT or ABI units that provide equipment and/or testing services. Two leading manufacturers of IIT equipment are Advanced Technology Corporation in the USA, and FRONTICS in Korea. In this investigation, FRONTICS kindly offered to collaborate with TWI on the project.

Underlying Principles

IIT is different from a conventional hardness test. For the purposes of determining tensile properties, a spherical indenter is driven at approximately constant speed into the surface of the material to be measured, Fig.1. The load required to reach the penetration depth is recorded. At specific depths, the indenter is unloaded and withdrawn slightly and then reloaded to a greater depth in a series of increments until the test is complete.

Figure 1. IIT unit magnetically attached to API 5L X60 pipe,showing umbilicals to a data processing computer.