“Measurement of hardness and elastic modulus by depth sensing indentation: further advances in understanding and refinements in methodology”
Sudharshan Phani Pardhasaradhi, ARCI
Dipartimento di Ingegneria
Laboratorio Interdipartimentale di Microscopia Elettronica (LIME), 7/10/2019 ore 12:00
Keywords: nanoindentation, hardness, elastic modulus, stiffness
Depth sensing indentation technique has been widely used to measure small scale mechanical properties over the years. Starting from the seminal work of Oliver & Pharr , there have been many improvements/modifications to the test methodology and significant advances in measurement electronics/testing instrumentation. These advancements provide opportunities to not only develop novel testing capabilities but also further improve the precision and accuracy of the most common measurement parameters – hardness and elastic modulus.
In this regard, a comprehensive study on the various steps involved in a typical depth sensing indentation test, viz., surface approach, surface detection, load-time history including superimposing an oscillatory force on broad band load, unloading and drift rate measurement will be presented. The effect of each of these steps on the accuracy and precision of the hardness and elastic modulus measurement will be discussed with specific focus on frequency specific testing techniques, such as continuous stiffness measurement. The effect of the instrument’s measurement time constants and dynamic parameters such as mass, spring constant and damping coefficient during different steps of an indentation test and thereby on the hardness and elastic modulus will be explained. With such a premise, specific insights on the recently developed High-speed nanoindentation mapping method will be, finally, presented.
 Oliver & Pharr, Journal of Materials Research, 7(6),1992.