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Open AccessFeature PaperArticle

Ultra High Strain Rate Nanoindentation Testing

International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur PO, Hyderabad, Telangana 500005, India
Nanomechanics Inc., 105 Meco Ln, Oak Ridge, TN 37830, USA
Author to whom correspondence should be addressed.
Materials 2017, 10(6), 663;
Received: 20 May 2017 / Revised: 13 June 2017 / Accepted: 14 June 2017 / Published: 17 June 2017
(This article belongs to the Special Issue Advanced Nanoindentation in Materials)
Strain rate dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of strain rates that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low noise levels (sub nanometer) at fast time constants (20 µs) and high data acquisition rates (100 KHz). These capabilities open the doors for a wide range of ultra-fast nanomechanical testing, for instance, indentation testing at very high strain rates. With an accurate dynamic model and an instrument with fast time constants, step load tests can be performed which enable access to indentation strain rates approaching ballistic levels (i.e., 4000 1/s). A novel indentation based testing technique involving a combination of step load and constant load and hold tests that enables measurement of strain rate dependence of hardness spanning over seven orders of magnitude in strain rate is presented. A simple analysis is used to calculate the equivalent uniaxial response from indentation data and compared to the conventional uniaxial data for commercial purity aluminum. Excellent agreement is found between the indentation and uniaxial data over several orders of magnitude of strain rate. View Full-Text
Keywords: high strain rate; nanoindentation; aluminum alloy; dynamics high strain rate; nanoindentation; aluminum alloy; dynamics
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MDPI and ACS Style

Sudharshan Phani, P.; Oliver, W.C. Ultra High Strain Rate Nanoindentation Testing. Materials 2017, 10, 663.

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