| About this Abstract |
| Meeting |
2020 TMS Annual Meeting & Exhibition
|
| Symposium
|
Nix Award and Lecture Symposium: Mechanistic Understanding of Mechanical Behavior Across Length Scales
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| Presentation Title |
Measurement of Mechanical Properties by Nanoindentation: Recent Innovations in Testing Methodology |
| Author(s) |
P Sudharshan Phani, Benoit Merle, Warren Oliver, George M. Pharr |
| On-Site Speaker (Planned) |
P Sudharshan Phani |
| Abstract Scope |
Great progress has been made over the past three decades in measuring mechanical properties at small scales by load- and depth-sensing indentation methods, also known as nanoindentation. Here, we outline a new innovation in nanoindentation testing motivated by a desire to make accurate hardness (H) and modulus (E) measurements in materials with extremely high E/H ratios, during very rapid testing used to map local properties, and in nanoindentation tests at very high strain rates (103 to 104 s-1). Under these conditions, the commonly used continuous stiffness method of property measurement (CSM) often breaks down because of what has been termed “plasticity error” - a measurement error that develops when loading conditions are such that a significant portion of the deformation in one oscillation cycle of the CSM measurement is plastic rather than elastic. Here, we show that by fully understanding how the phase-lock amplifier measures the contact stiffness from small oscillations in the applied force or displacement, plasticity errors can be modeled and understood, and largely corrected. The observations and analysis also suggest that there are much better ways to make CSM measurements rather than the commonly used technique of applying small oscillations at fixed displacement amplitude. The new observations and analysis procedures are documented and verified by experimental measurements in two model materials - fused silica and aluminum.
* Work sponsored in part by the U.S. Department of Energy, National Nuclear Security Administration, under Award No. DE-NA0003857. |
| Proceedings Inclusion? |
Undecided |