Nano-indentation is a depth sensing indentation technique, which promises to become an important mechanical characterisation tool for structures such as coatings and small areas of components, right down to probing individual fibres in composites or specific grains in welds. It can be applied to all material groups including metals, ceramics, composites, polymers and biological tissues.
By using a nano-indenter, which can sample directly from the area of interest, engineers can begin to predict much more accurately how their products will behave. As the indenter is driven in and out of a sample at constant load, its penetration depth is continuously monitored. The resultant load-depth curve gives the information needed to determine hardness, elastic modulus and other material properties. This gives accurate material property values with penetration depths as low as a few nanometres.
Mapping of surface properties across small areas
The elastic and plastic properties of materials at the nano-scale
Mechanical property measurement of individual phases or grains
Nano-scratch and wear testing to help solve coating problems, such as delamination and abrasive wear, that have a direct bearing on ultimate performance.
Nano-indentation probes mechanical properties at high strain rate, investigating surface fatigue and fracture due to repetitive impact.
Testing under heated and cooled conditions (-30 to 750°C)
Testing in liquid environments
These techniques provide application-specific data complementary to conventional macro-scale test data which allows accurate simulation in the laboratory environment of the results of larger scale, expensive field testing.
Nano-indentation was used during two recent TWI projects; to access dissimilar metal interfaces for sub-sea applications and adhesion of transparent conductive oxides onto different substrates. This type of information may help to improve finite element simulations for reliability prediction of joined structures.
Typical failure modes of transparent conductive oxides deposited onto different substrates: PEN, glass and Si.
LCE-MTC is part-financed by the European Union's ERDF Competitiveness Programme 2007-13, securing £1.7m ERDF investment through One North East. The ERDF programme is bringing over £250m into the North East to support innovation, enterprise and business support across the region and aims to help create and safeguard 28,000 new jobs, start 3,000 new businesses and increase the region's productivity by £1.1bn per annum.
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