TWI Industrial Member Report Summary 837/2005
By A Motarjemi
Technology to determine the mechanical properties of materials without the need to take a sample is of great importance to many parts of industry. It is particularly important to the power and oil and gas industries for the assessment of ageing equipment, where original data or material may not be available or where it may not be possible to extract a sample. Characterisation of the properties of narrow-gap, electron beam or laser welds is another area of interest, since it is difficult to design a test specimen that can measure the local properties over short distances.
In 2003, TWI undertook an exploratory project to compile and review the testing techniques available for determining the properties of material either in-situ on the component, or from small samples. Among those techniques for the determination of tensile properties in-situ was the instrumented indentation technique (IIT). In this project, TWI has investigated and independently evaluated the capability, usefulness and limitations of the IIT.
In this report, TWI describes the principles of the technique and the equipment, and comments on its practical experience of using it. The tensile properties of a range of materials, welds and components were estimated using the IIT, and compared with the results from conventional tensile tests. In some cases they were compared with the results from micro-flat tensile testing (MFT) and hardness testing.
- To evaluate the instrumented indentation technique (IIT) as a means to determine the tensile properties of materials by comparison with conventional tensile testing, hardness correlation and miniaturised tensile testing techniques.
- To determine the advantages and limitations of the instrumented indentation technique (IIT) for determining the tensile properties required for engineering critical assessments of components.