A. Lambai; N.G. Mathews; S.P. Bhusare; A. Sharma; X. Maeder; L. Pethö; J. Pakarinen; J. Schwiedrzik; J. Michler; R. Ramachandramoorthy; G. Mohant
Materials & Design 258 (2025) 114720
High strain rate testing at micrometer length scale is crucial for understanding the fundamental deformation mechanisms and identifying potential changes asso
ciated with varying strain rates. However, the technique is not well established due to instrumental limitations and the lack of standardized experimental protocols.
This hinders the investigation of deformation mechanisms of materials at high strain rates and limits its incorporation into computational models. This work focuses
on the experimental considerations in designing constant strain rate (CSR) nanoindentation measurements up to 104 s−1 strain rate. An extensive study was con
ducted on three materials – fused silica (FS), nanocrystalline nickel (nc Ni), single crystal nickel (sx Ni) – to validate the experimental approach, explore potential
artefacts, study strain rate sensitivity of hardness, and understand the underlying deformation mechanisms at high strain rates. For all materials, the hardness
increased with strain rate and the strain rate sensitivity remained constant. For sx Ni, the formation of sub-grain boundaries was found to be responsible for the
observed increased strain rate sensitivity exponent. However, the results indicate no change in the deformation mechanisms across seven orders of strain rates from
10−2 s−1 to 104 s−1 in the tested materials.