Instrumented Indentation Technique (IIT)

Structures constructed in the rapid economic growth age of 1970s have been seriously deteriorated by continuous use for more than 30 years, and this may cause large industrial disasters.

Therefore, for safe use of such aged facilities, it is necessary to estimate precise life by evaluating properties on the materials regularly. 

For safe use and maintenance of obsolete equipment, it is necessary to adopt the technology that allows monitoring material characteristics according to age-related degradation in industry fields in addition to the existing laboratory based mechanical properties evaluation method. It is also urgently needed to complement the system (Instrumented Indentation Technique), the system obtains/collects data of material degradation and life prediction to determine the risk and periodic time of inspection of the equipment and it then determines time to replace and repair.

For industry utilization of developed materials, it is important to obtain reliability of materials and parts based on properties accumulation by applying appropriate evaluation method. However, existing standard method for material properties assessment of uniaxial tensile and fracture mechanics provide considerable information on transformation and destruction behavior, but it require bulk specimen which can be damaged on facilities and structures with notch while collecting specimen from, so it ironically can harm the safety of structures, and even worse, specimen taken on properties may be different from original properties of structure at the site as a result of relaxed stress and damage made while being collected.

To consider the requirements of test method to apply properties evaluation in micro materials, it should be able to evaluate hundreds of Å thin film thickness alone, and it should be able to limit the properties evaluation area to inner part of grain to evaluate mechanical properties of each phase.

To solve the said problems, automated indentation testing method which is semi non-destructive, and simple to operate directly on site and nano indentation test method which holds nm indentation depth with extreme low load are proposed.

Unlike existing hardness test method that measures hardness alone, these testing methods obtain the indentation load-depth curve and measures various mechanical properties related to deformation and fracture with the indentation load-depth curve. With automated indentation testing method, it is able to measure not only hardness but also the flow properties including yield strength, tensile strength and strain hardening index and also, it is able to evaluate characteristics of fracture with appropriate modeling.

Researches regarding nano indentation testing method were mainly focused on evaluating hardness and elasticity modulus on thin film and Nano phase by using a sharp indenter with certain angle. But recently, researches are on progress to assess high-level properties like flow curve by integrating analyzed technology from automated indentation testing method(Instrumented Indentation Technique).

Table of Contents

1. Outline of IIT (Instrumented Indentation Technique)
2. Application of Advanced Indentation System
3. Macro scale mechanical properties evaluation
A. Contact properties
B. Flow properties
C. Yield strength
D. Strain hardening exponent
E. Indentation strength
F. Non-uniform elongation
G. Fracture toughness

4. Micro mechanic properties evaluation
A. Elasticity modulus and hardness of thin film

5. Summary
A Summary and References